SELECT table_name, column_name FROM information_schema.columns where table_name="OPTIMIZER_TRACE";
table_name column_name
OPTIMIZER_TRACE QUERY
OPTIMIZER_TRACE TRACE
OPTIMIZER_TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE
OPTIMIZER_TRACE INSUFFICIENT_PRIVILEGES
set optimizer_trace="enabled=on";
show variables like 'optimizer_trace';
Variable_name Value
optimizer_trace enabled=on
set optimizer_trace="enabled=off";
show variables like 'optimizer_trace';
Variable_name Value
optimizer_trace enabled=off
create table t1 (a int, b int);
insert into t1 values (1,2),(2,3);
create table t2 (b int);
insert into t2 values (1),(2);
analyze table t1;
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status OK
analyze table t2;
Table Op Msg_type Msg_text
test.t2 analyze status Engine-independent statistics collected
test.t2 analyze status OK
create function f1 (a int) returns INT
return 1;
create view v1 as select * from t1 where t1.a=1;
create view v2 as select * from t1 where t1.a=1 group by t1.b;
set optimizer_trace="enabled=on";
# Mergeable views/derived tables
select * from v1;
a b
1 2
select * from information_schema.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
select * from v1 {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"view": {
"table": "v1",
"select_id": 2,
"algorithm": "merged"
}
},
{
"join_preparation": {
"select_id": 2,
"steps": [
{
"expanded_query": "/* select#2 */ select t1.a AS a,t1.b AS b from t1 where t1.a = 1"
}
]
}
},
{
"expanded_query": "/* select#1 */ select t1.a AS a,t1.b AS b from v1"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "t1.a = 1",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "multiple equal(1, t1.a)"
},
{
"transformation": "constant_propagation",
"resulting_condition": "multiple equal(1, t1.a)"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "multiple equal(1, t1.a)"
}
]
}
},
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": []
},
{
"rows_estimation": [
{
"selectivity_for_indexes": [],
"selectivity_for_columns": [
{
"column_name": "a",
"ranges": ["1 <= a <= 1"],
"selectivity_from_histogram": 0.5
}
],
"cond_selectivity": 0.5
},
{
"table": "t1",
"table_scan": {
"rows": 2,
"cost": 2.004394531
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 1,
"cost": 2.204394531,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 1,
"cost": 2.204394531,
"uses_join_buffering": false
}
},
"rows_for_plan": 1,
"cost_for_plan": 2.404394531,
"estimated_join_cardinality": 1
}
]
},
{
"best_join_order": ["t1"]
},
{
"attaching_conditions_to_tables": {
"original_condition": "t1.a = 1",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": "t1.a = 1"
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
select * from (select * from t1 where t1.a=1)q;
a b
1 2
select * from information_schema.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
select * from (select * from t1 where t1.a=1)q {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"derived": {
"table": "q",
"select_id": 2,
"algorithm": "merged"
}
},
{
"join_preparation": {
"select_id": 2,
"steps": [
{
"expanded_query": "/* select#2 */ select t1.a AS a,t1.b AS b from t1 where t1.a = 1"
}
]
}
},
{
"expanded_query": "/* select#1 */ select t1.a AS a,t1.b AS b from (/* select#2 */ select t1.a AS a,t1.b AS b from t1 where t1.a = 1) q"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "t1.a = 1",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "multiple equal(1, t1.a)"
},
{
"transformation": "constant_propagation",
"resulting_condition": "multiple equal(1, t1.a)"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "multiple equal(1, t1.a)"
}
]
}
},
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": []
},
{
"rows_estimation": [
{
"selectivity_for_indexes": [],
"selectivity_for_columns": [
{
"column_name": "a",
"ranges": ["1 <= a <= 1"],
"selectivity_from_histogram": 0.5
}
],
"cond_selectivity": 0.5
},
{
"table": "t1",
"table_scan": {
"rows": 2,
"cost": 2.004394531
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 1,
"cost": 2.204394531,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 1,
"cost": 2.204394531,
"uses_join_buffering": false
}
},
"rows_for_plan": 1,
"cost_for_plan": 2.404394531,
"estimated_join_cardinality": 1
}
]
},
{
"best_join_order": ["t1"]
},
{
"attaching_conditions_to_tables": {
"original_condition": "t1.a = 1",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": "t1.a = 1"
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
# Non-Mergeable views
select * from v2;
a b
1 2
select * from information_schema.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
select * from v2 {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"view": {
"table": "v2",
"select_id": 2,
"algorithm": "materialized"
}
},
{
"join_preparation": {
"select_id": 2,
"steps": [
{
"expanded_query": "/* select#2 */ select t1.a AS a,t1.b AS b from t1 where t1.a = 1 group by t1.b"
}
]
}
},
{
"expanded_query": "/* select#1 */ select v2.a AS a,v2.b AS b from v2"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"join_optimization": {
"select_id": 2,
"steps": [
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "t1.a = 1",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "multiple equal(1, t1.a)"
},
{
"transformation": "constant_propagation",
"resulting_condition": "multiple equal(1, t1.a)"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "multiple equal(1, t1.a)"
}
]
}
},
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": []
},
{
"rows_estimation": [
{
"selectivity_for_indexes": [],
"selectivity_for_columns": [
{
"column_name": "a",
"ranges": ["1 <= a <= 1"],
"selectivity_from_histogram": 0.5
}
],
"cond_selectivity": 0.5
},
{
"table": "t1",
"table_scan": {
"rows": 2,
"cost": 2.004394531
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 1,
"cost": 2.204394531,
"chosen": true,
"use_tmp_table": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 1,
"cost": 2.204394531,
"uses_join_buffering": false
}
},
"rows_for_plan": 1,
"cost_for_plan": 2.404394531,
"cost_for_sorting": 1,
"estimated_join_cardinality": 1
}
]
},
{
"check_split_materialized": {
"not_applicable": "no candidate field can be accessed through ref"
}
},
{
"best_join_order": ["t1"]
},
{
"attaching_conditions_to_tables": {
"original_condition": "t1.a = 1",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": "t1.a = 1"
}
]
}
},
{
"test_if_skip_sort_order": []
}
]
}
},
{
"table_dependencies": [
{
"table": "<derived2>",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"rows_estimation": [
{
"table": "<derived2>",
"table_scan": {
"rows": 2,
"cost": 2
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "<derived2>",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 2,
"cost": 2,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 2,
"cost": 2,
"uses_join_buffering": false
}
},
"rows_for_plan": 2,
"cost_for_plan": 2.4,
"estimated_join_cardinality": 2
}
]
},
{
"best_join_order": ["<derived2>"]
},
{
"attaching_conditions_to_tables": {
"original_condition": null,
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "<derived2>",
"attached": null
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": [
{
"join_execution": {
"select_id": 2,
"steps": []
}
}
]
}
}
]
} 0 0
drop table t1,t2;
drop view v1,v2;
drop function f1;
create table t1(a int, b int);
insert into t1 values (0,0),(1,1),(2,1),(3,2),(4,3),
(5,3),(6,3),(7,3),(8,3),(9,3);
create table t2(a int, b int);
insert into t2 values (0,0),(1,1),(2,1),(3,2),(4,3),
(5,3),(6,3),(7,3),(8,3),(9,3);
ANALYZE TABLE t1;
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status OK
ANALYZE TABLE t2;
Table Op Msg_type Msg_text
test.t2 analyze status Engine-independent statistics collected
test.t2 analyze status OK
create view v1 as select a from t1 group by b;
create view v2 as select a from t2;
# Mergeable view
explain select * from v2 ;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 10
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain select * from v2 {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"view": {
"table": "v2",
"select_id": 2,
"algorithm": "merged"
}
},
{
"join_preparation": {
"select_id": 2,
"steps": [
{
"expanded_query": "/* select#2 */ select t2.a AS a from t2"
}
]
}
},
{
"expanded_query": "/* select#1 */ select t2.a AS a from v2"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"table_dependencies": [
{
"table": "t2",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"rows_estimation": [
{
"table": "t2",
"table_scan": {
"rows": 10,
"cost": 2.021972656
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 10,
"cost": 2.021972656,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 10,
"cost": 2.021972656,
"uses_join_buffering": false
}
},
"rows_for_plan": 10,
"cost_for_plan": 4.021972656,
"estimated_join_cardinality": 10
}
]
},
{
"best_join_order": ["t2"]
},
{
"attaching_conditions_to_tables": {
"original_condition": null,
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t2",
"attached": null
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
# Non-Mergeable view
explain select * from v1 ;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 10
2 DERIVED t1 ALL NULL NULL NULL NULL 10 Using temporary; Using filesort
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain select * from v1 {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"view": {
"table": "v1",
"select_id": 2,
"algorithm": "materialized"
}
},
{
"join_preparation": {
"select_id": 2,
"steps": [
{
"expanded_query": "/* select#2 */ select t1.a AS a from t1 group by t1.b"
}
]
}
},
{
"expanded_query": "/* select#1 */ select v1.a AS a from v1"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"join_optimization": {
"select_id": 2,
"steps": [
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"rows_estimation": [
{
"table": "t1",
"table_scan": {
"rows": 10,
"cost": 2.021972656
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 10,
"cost": 2.021972656,
"chosen": true,
"use_tmp_table": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 10,
"cost": 2.021972656,
"uses_join_buffering": false
}
},
"rows_for_plan": 10,
"cost_for_plan": 4.021972656,
"cost_for_sorting": 10,
"estimated_join_cardinality": 10
}
]
},
{
"check_split_materialized": {
"not_applicable": "group list has no candidates"
}
},
{
"best_join_order": ["t1"]
},
{
"attaching_conditions_to_tables": {
"original_condition": null,
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": null
}
]
}
},
{
"test_if_skip_sort_order": []
}
]
}
},
{
"table_dependencies": [
{
"table": "<derived2>",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"rows_estimation": [
{
"table": "<derived2>",
"table_scan": {
"rows": 10,
"cost": 10
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "<derived2>",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 10,
"cost": 10,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 10,
"cost": 10,
"uses_join_buffering": false
}
},
"rows_for_plan": 10,
"cost_for_plan": 12,
"estimated_join_cardinality": 10
}
]
},
{
"best_join_order": ["<derived2>"]
},
{
"attaching_conditions_to_tables": {
"original_condition": null,
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "<derived2>",
"attached": null
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": [
{
"join_execution": {
"select_id": 2,
"steps": []
}
}
]
}
}
]
} 0 0
drop table t1,t2;
drop view v1,v2;
#
# print ref-keyues array
#
create table t0 (a int);
INSERT INTO t0 VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t1 (a int, b int, c int, key(a));
insert into t1 select A.a*10 + B.a, A.a*10 + B.a, A.a*10 + B.a from t0 A, t0 B;
create table t2(a int, b int, c int , key(a));
insert into t2 select A.a*10 + B.a, A.a*10 + B.a, A.a*10 + B.a from t0 A, t0 B;
analyze table t1;
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status Table is already up to date
analyze table t2;
Table Op Msg_type Msg_text
test.t2 analyze status Engine-independent statistics collected
test.t2 analyze status Table is already up to date
explain select * from t1,t2 where t1.a=t2.b+2 and t2.a= t1.b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL a NULL NULL NULL 100 Using where
1 SIMPLE t2 ref a a 5 test.t1.b 1 Using where
select * from information_schema.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain select * from t1,t2 where t1.a=t2.b+2 and t2.a= t1.b {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "select t1.a AS a,t1.b AS b,t1.c AS c,t2.a AS a,t2.b AS b,t2.c AS c from t1 join t2 where t1.a = t2.b + 2 and t2.a = t1.b"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "t1.a = t2.b + 2 and t2.a = t1.b",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "t1.a = t2.b + 2 and multiple equal(t2.a, t1.b)"
},
{
"transformation": "constant_propagation",
"resulting_condition": "t1.a = t2.b + 2 and multiple equal(t2.a, t1.b)"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "t1.a = t2.b + 2 and multiple equal(t2.a, t1.b)"
}
]
}
},
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
},
{
"table": "t2",
"row_may_be_null": false,
"map_bit": 1,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": [
{
"table": "t1",
"field": "a",
"equals": "t2.b + 2",
"null_rejecting": true
},
{
"table": "t2",
"field": "a",
"equals": "t1.b",
"null_rejecting": true
}
]
},
{
"rows_estimation": [
{
"table": "t1",
"table_scan": {
"rows": 100,
"cost": 2.317382812
}
},
{
"table": "t2",
"table_scan": {
"rows": 100,
"cost": 2.317382812
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 100,
"cost": 2.317382812,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 100,
"cost": 2.317382812,
"uses_join_buffering": false
}
},
"rows_for_plan": 100,
"cost_for_plan": 22.31738281,
"rest_of_plan": [
{
"plan_prefix": ["t1"],
"table": "t2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "ref",
"index": "a",
"used_range_estimates": false,
"cause": "not available",
"rows": 1,
"cost": 200.0585794,
"chosen": true
},
{
"access_type": "scan",
"resulting_rows": 100,
"cost": 2.317382812,
"chosen": false
}
],
"chosen_access_method": {
"type": "ref",
"records": 1,
"cost": 200.0585794,
"uses_join_buffering": false
}
},
"rows_for_plan": 100,
"cost_for_plan": 242.3759623,
"estimated_join_cardinality": 100
}
]
},
{
"plan_prefix": [],
"table": "t2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 100,
"cost": 2.317382812,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 100,
"cost": 2.317382812,
"uses_join_buffering": false
}
},
"rows_for_plan": 100,
"cost_for_plan": 22.31738281,
"rest_of_plan": [
{
"plan_prefix": ["t2"],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "ref",
"index": "a",
"used_range_estimates": false,
"cause": "not available",
"rows": 1,
"cost": 200.0585794,
"chosen": true
},
{
"access_type": "scan",
"resulting_rows": 100,
"cost": 2.317382812,
"chosen": false
}
],
"chosen_access_method": {
"type": "ref",
"records": 1,
"cost": 200.0585794,
"uses_join_buffering": false
}
},
"rows_for_plan": 100,
"cost_for_plan": 242.3759623,
"pruned_by_cost": true
}
]
}
]
},
{
"best_join_order": ["t1", "t2"]
},
{
"attaching_conditions_to_tables": {
"original_condition": "t2.a = t1.b and t1.a = t2.b + 2",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": "t1.b is not null"
},
{
"table": "t2",
"attached": "t1.a = t2.b + 2"
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
drop table t1,t2,t0;
#
# group_by min max optimization
#
CREATE TABLE t1 (id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, a INT NOT NULL, KEY(a));
analyze table t1;
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status OK
EXPLAIN SELECT DISTINCT a FROM t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range NULL a 4 NULL 5 Using index for group-by
select * from information_schema.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
EXPLAIN SELECT DISTINCT a FROM t1 {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "select distinct t1.a AS a from t1"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"rows_estimation": [
{
"table": "t1",
"range_analysis": {
"table_scan": {
"rows": 65536,
"cost": 13255.2
},
"potential_range_indexes": [
{
"index": "PRIMARY",
"usable": false,
"cause": "not applicable"
},
{
"index": "a",
"usable": true,
"key_parts": ["a"]
}
],
"best_covering_index_scan": {
"index": "a",
"cost": 13377.39141,
"chosen": false,
"cause": "cost"
},
"group_index_range": {
"distinct_query": true,
"potential_group_range_indexes": [
{
"index": "a",
"covering": true,
"rows": 5,
"cost": 6.25
}
]
},
"best_group_range_summary": {
"type": "index_group",
"index": "a",
"min_max_arg": null,
"min_aggregate": false,
"max_aggregate": false,
"distinct_aggregate": false,
"rows": 5,
"cost": 6.25,
"key_parts_used_for_access": ["a"],
"ranges": [],
"chosen": true
},
"chosen_range_access_summary": {
"range_access_plan": {
"type": "index_group",
"index": "a",
"min_max_arg": null,
"min_aggregate": false,
"max_aggregate": false,
"distinct_aggregate": false,
"rows": 5,
"cost": 6.25,
"key_parts_used_for_access": ["a"],
"ranges": []
},
"rows_for_plan": 5,
"cost_for_plan": 6.25,
"chosen": true
}
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "index_merge",
"resulting_rows": 5,
"cost": 6.25,
"chosen": true
}
],
"chosen_access_method": {
"type": "index_merge",
"records": 5,
"cost": 6.25,
"uses_join_buffering": false
}
},
"rows_for_plan": 5,
"cost_for_plan": 7.25,
"estimated_join_cardinality": 5
}
]
},
{
"best_join_order": ["t1"]
},
{
"attaching_conditions_to_tables": {
"original_condition": null,
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": null
}
]
}
},
{
"test_if_skip_sort_order": []
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
drop table t1;
#
# With group by , where clause and MIN/MAX function
#
CREATE TABLE t1 (a INT, b INT, c int, d int, KEY(a,b,c,d));
INSERT INTO t1 VALUES (1,1,1,1), (2,2,2,2), (3,3,3,3), (4,4,4,4), (1,0,1,1), (3,2,3,3), (4,5,4,4);
ANALYZE TABLE t1;
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status OK
EXPLAIN SELECT MIN(d) FROM t1 where b=2 and c=3 group by a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range NULL a 20 NULL 8 Using where; Using index for group-by
select * from information_schema.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
EXPLAIN SELECT MIN(d) FROM t1 where b=2 and c=3 group by a {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "select min(t1.d) AS `MIN(d)` from t1 where t1.b = 2 and t1.c = 3 group by t1.a"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "t1.b = 2 and t1.c = 3",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "multiple equal(2, t1.b) and multiple equal(3, t1.c)"
},
{
"transformation": "constant_propagation",
"resulting_condition": "multiple equal(2, t1.b) and multiple equal(3, t1.c)"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "multiple equal(2, t1.b) and multiple equal(3, t1.c)"
}
]
}
},
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": []
},
{
"rows_estimation": [
{
"table": "t1",
"range_analysis": {
"table_scan": {
"rows": 7,
"cost": 5.429052734
},
"potential_range_indexes": [
{
"index": "a",
"usable": true,
"key_parts": ["a", "b", "c", "d"]
}
],
"best_covering_index_scan": {
"index": "a",
"cost": 2.409226263,
"chosen": true
},
"setup_range_conditions": [],
"analyzing_range_alternatives": {
"range_scan_alternatives": [],
"analyzing_roworder_intersect": {
"cause": "too few roworder scans"
},
"analyzing_index_merge_union": []
},
"group_index_range": {
"potential_group_range_indexes": [
{
"index": "a",
"covering": true,
"ranges": ["(2,3) <= (b,c) <= (2,3)"],
"rows": 8,
"cost": 2.2
}
]
},
"best_group_range_summary": {
"type": "index_group",
"index": "a",
"min_max_arg": "d",
"min_aggregate": true,
"max_aggregate": false,
"distinct_aggregate": false,
"rows": 8,
"cost": 2.2,
"key_parts_used_for_access": ["a", "b", "c"],
"ranges": ["(2,3) <= (b,c) <= (2,3)"],
"chosen": true
},
"chosen_range_access_summary": {
"range_access_plan": {
"type": "index_group",
"index": "a",
"min_max_arg": "d",
"min_aggregate": true,
"max_aggregate": false,
"distinct_aggregate": false,
"rows": 8,
"cost": 2.2,
"key_parts_used_for_access": ["a", "b", "c"],
"ranges": ["(2,3) <= (b,c) <= (2,3)"]
},
"rows_for_plan": 8,
"cost_for_plan": 2.2,
"chosen": true
}
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "index_merge",
"resulting_rows": 8,
"cost": 2.2,
"chosen": true,
"use_tmp_table": true
}
],
"chosen_access_method": {
"type": "index_merge",
"records": 8,
"cost": 2.2,
"uses_join_buffering": false
}
},
"rows_for_plan": 8,
"cost_for_plan": 3.8,
"cost_for_sorting": 8,
"estimated_join_cardinality": 8
}
]
},
{
"best_join_order": ["t1"]
},
{
"attaching_conditions_to_tables": {
"original_condition": "t1.b = 2 and t1.c = 3",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": "t1.b = 2 and t1.c = 3"
}
]
}
},
{
"test_if_skip_sort_order": []
},
{
"prepare_sum_aggregators": {
"function": "min(t1.d)",
"aggregator_type": "simple"
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
DROP TABLE t1;
CREATE TABLE t1 (id INT NOT NULL, a DATE, KEY(id,a));
INSERT INTO t1 values (1,'2001-01-01'),(1,'2001-01-02'),
(1,'2001-01-03'),(1,'2001-01-04'),
(2,'2001-01-01'),(2,'2001-01-02'),
(2,'2001-01-03'),(2,'2001-01-04'),
(3,'2001-01-01'),(3,'2001-01-02'),
(3,'2001-01-03'),(3,'2001-01-04'),
(4,'2001-01-01'),(4,'2001-01-02'),
(4,'2001-01-03'),(4,'2001-01-04');
set optimizer_trace='enabled=on';
EXPLAIN SELECT id,MIN(a),MAX(a) FROM t1 WHERE a>=20010104e0 GROUP BY id;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range NULL id 8 NULL 9 Using where; Using index for group-by
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
EXPLAIN SELECT id,MIN(a),MAX(a) FROM t1 WHERE a>=20010104e0 GROUP BY id {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "select t1.`id` AS `id`,min(t1.a) AS `MIN(a)`,max(t1.a) AS `MAX(a)` from t1 where t1.a >= 20010104e0 group by t1.`id`"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "t1.a >= 20010104e0",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "t1.a >= 20010104e0"
},
{
"transformation": "constant_propagation",
"resulting_condition": "t1.a >= 20010104e0"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "t1.a >= 20010104e0"
}
]
}
},
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": []
},
{
"rows_estimation": [
{
"table": "t1",
"range_analysis": {
"table_scan": {
"rows": 16,
"cost": 7.23125
},
"potential_range_indexes": [
{
"index": "id",
"usable": true,
"key_parts": ["id", "a"]
}
],
"best_covering_index_scan": {
"index": "id",
"cost": 4.21171589,
"chosen": true
},
"setup_range_conditions": [],
"analyzing_range_alternatives": {
"range_scan_alternatives": [],
"analyzing_roworder_intersect": {
"cause": "too few roworder scans"
},
"analyzing_index_merge_union": []
},
"group_index_range": {
"potential_group_range_indexes": [
{
"index": "id",
"covering": true,
"ranges": ["(2001-01-04) <= (a)"],
"rows": 9,
"cost": 2.35
}
]
},
"best_group_range_summary": {
"type": "index_group",
"index": "id",
"min_max_arg": "a",
"min_aggregate": true,
"max_aggregate": true,
"distinct_aggregate": false,
"rows": 9,
"cost": 2.35,
"key_parts_used_for_access": ["id"],
"ranges": ["(2001-01-04) <= (a)"],
"chosen": true
},
"chosen_range_access_summary": {
"range_access_plan": {
"type": "index_group",
"index": "id",
"min_max_arg": "a",
"min_aggregate": true,
"max_aggregate": true,
"distinct_aggregate": false,
"rows": 9,
"cost": 2.35,
"key_parts_used_for_access": ["id"],
"ranges": ["(2001-01-04) <= (a)"]
},
"rows_for_plan": 9,
"cost_for_plan": 2.35,
"chosen": true
}
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "index_merge",
"resulting_rows": 9,
"cost": 2.35,
"chosen": true,
"use_tmp_table": true
}
],
"chosen_access_method": {
"type": "index_merge",
"records": 9,
"cost": 2.35,
"uses_join_buffering": false
}
},
"rows_for_plan": 9,
"cost_for_plan": 4.15,
"cost_for_sorting": 9,
"estimated_join_cardinality": 9
}
]
},
{
"best_join_order": ["t1"]
},
{
"attaching_conditions_to_tables": {
"original_condition": "t1.a >= 20010104e0",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": "t1.a >= 20010104e0"
}
]
}
},
{
"test_if_skip_sort_order": []
},
{
"prepare_sum_aggregators": {
"function": "min(t1.a)",
"aggregator_type": "simple"
}
},
{
"prepare_sum_aggregators": {
"function": "max(t1.a)",
"aggregator_type": "simple"
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
EXPLAIN SELECT * FROM t1 WHERE a = 20010104e0 GROUP BY id;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range NULL id 8 NULL 9 Using where; Using index for group-by
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
EXPLAIN SELECT * FROM t1 WHERE a = 20010104e0 GROUP BY id {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "select t1.`id` AS `id`,t1.a AS a from t1 where t1.a = 20010104e0 group by t1.`id`"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "t1.a = 20010104e0",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "t1.a = 20010104e0"
},
{
"transformation": "constant_propagation",
"resulting_condition": "t1.a = 20010104e0"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "t1.a = 20010104e0"
}
]
}
},
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": []
},
{
"rows_estimation": [
{
"table": "t1",
"range_analysis": {
"table_scan": {
"rows": 16,
"cost": 7.23125
},
"potential_range_indexes": [
{
"index": "id",
"usable": true,
"key_parts": ["id", "a"]
}
],
"best_covering_index_scan": {
"index": "id",
"cost": 4.21171589,
"chosen": true
},
"setup_range_conditions": [],
"analyzing_range_alternatives": {
"range_scan_alternatives": [],
"analyzing_roworder_intersect": {
"cause": "too few roworder scans"
},
"analyzing_index_merge_union": []
},
"group_index_range": {
"potential_group_range_indexes": [
{
"index": "id",
"covering": true,
"ranges": ["(2001-01-04) <= (a) <= (2001-01-04)"],
"rows": 9,
"cost": 2.35
}
]
},
"best_group_range_summary": {
"type": "index_group",
"index": "id",
"min_max_arg": null,
"min_aggregate": false,
"max_aggregate": false,
"distinct_aggregate": false,
"rows": 9,
"cost": 2.35,
"key_parts_used_for_access": ["id", "a"],
"ranges": ["(2001-01-04) <= (a) <= (2001-01-04)"],
"chosen": true
},
"chosen_range_access_summary": {
"range_access_plan": {
"type": "index_group",
"index": "id",
"min_max_arg": null,
"min_aggregate": false,
"max_aggregate": false,
"distinct_aggregate": false,
"rows": 9,
"cost": 2.35,
"key_parts_used_for_access": ["id", "a"],
"ranges": ["(2001-01-04) <= (a) <= (2001-01-04)"]
},
"rows_for_plan": 9,
"cost_for_plan": 2.35,
"chosen": true
}
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "index_merge",
"resulting_rows": 9,
"cost": 2.35,
"chosen": true,
"use_tmp_table": true
}
],
"chosen_access_method": {
"type": "index_merge",
"records": 9,
"cost": 2.35,
"uses_join_buffering": false
}
},
"rows_for_plan": 9,
"cost_for_plan": 4.15,
"cost_for_sorting": 9,
"estimated_join_cardinality": 9
}
]
},
{
"best_join_order": ["t1"]
},
{
"attaching_conditions_to_tables": {
"original_condition": "t1.a = 20010104e0",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": "t1.a = 20010104e0"
}
]
}
},
{
"test_if_skip_sort_order": []
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
drop table t1;
#
# Late ORDER BY optimization
#
create table ten(a int);
insert into ten values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table one_k(a int primary key);
insert into one_k select A.a + B.a* 10 + C.a * 100 from ten A, ten B, ten C;
create table t1 (
pk int not null,
a int,
b int,
c int,
filler char(100),
KEY a_a(c),
KEY a_c(a,c),
KEY a_b(a,b)
);
insert into t1
select a, a,a,a, 'filler-dataaa' from test.one_k;
update t1 set a=1 where pk between 0 and 180;
update t1 set b=2 where pk between 0 and 20;
analyze table t1;
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status OK
set optimizer_trace='enabled=on';
explain select * from t1 where a=1 and b=2 order by c limit 1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range a_c,a_b a_c 5 NULL 180 Using where
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain select * from t1 where a=1 and b=2 order by c limit 1 {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "select t1.pk AS pk,t1.a AS a,t1.b AS b,t1.c AS c,t1.filler AS filler from t1 where t1.a = 1 and t1.b = 2 order by t1.c limit 1"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "t1.a = 1 and t1.b = 2",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "multiple equal(1, t1.a) and multiple equal(2, t1.b)"
},
{
"transformation": "constant_propagation",
"resulting_condition": "multiple equal(1, t1.a) and multiple equal(2, t1.b)"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "multiple equal(1, t1.a) and multiple equal(2, t1.b)"
}
]
}
},
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": [
{
"table": "t1",
"field": "a",
"equals": "1",
"null_rejecting": true
},
{
"table": "t1",
"field": "a",
"equals": "1",
"null_rejecting": true
},
{
"table": "t1",
"field": "b",
"equals": "2",
"null_rejecting": true
}
]
},
{
"rows_estimation": [
{
"table": "t1",
"range_analysis": {
"table_scan": {
"rows": 1000,
"cost": 232.5644531
},
"potential_range_indexes": [
{
"index": "a_a",
"usable": false,
"cause": "not applicable"
},
{
"index": "a_c",
"usable": true,
"key_parts": ["a", "c"]
},
{
"index": "a_b",
"usable": true,
"key_parts": ["a", "b"]
}
],
"setup_range_conditions": [],
"analyzing_range_alternatives": {
"range_scan_alternatives": [
{
"index": "a_c",
"ranges": ["(1) <= (a) <= (1)"],
"rowid_ordered": false,
"using_mrr": false,
"index_only": false,
"rows": 180,
"cost": 216.2943776,
"chosen": true
},
{
"index": "a_b",
"ranges": ["(1,2) <= (a,b) <= (1,2)"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": false,
"rows": 21,
"cost": 25.36242739,
"chosen": true
}
],
"analyzing_roworder_intersect": {
"cause": "too few roworder scans"
},
"analyzing_index_merge_union": []
},
"group_index_range": {
"chosen": false,
"cause": "no group by or distinct"
},
"chosen_range_access_summary": {
"range_access_plan": {
"type": "range_scan",
"index": "a_b",
"rows": 21,
"ranges": ["(1,2) <= (a,b) <= (1,2)"]
},
"rows_for_plan": 21,
"cost_for_plan": 25.36242739,
"chosen": true
}
}
},
{
"table": "t1",
"rowid_filters": [
{
"key": "a_b",
"build_cost": 0.886777098,
"rows": 21
},
{
"key": "a_c",
"build_cost": 10.52169992,
"rows": 180
}
]
},
{
"selectivity_for_indexes": [
{
"index_name": "a_b",
"selectivity_from_index": 0.021
}
],
"selectivity_for_columns": [
{
"column_name": "a",
"ranges": ["1 <= a <= 1"],
"selectivity_from_histogram": 0.1796875
},
{
"column_name": "b",
"ranges": ["2 <= b <= 2"],
"selectivity_from_histogram": 0.015625
}
],
"cond_selectivity": 0.021
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "ref",
"index": "a_c",
"used_range_estimates": true,
"rowid_filter_skipped": "worst/max seeks clipping",
"rows": 180,
"cost": 180.2743776,
"chosen": true
},
{
"access_type": "ref",
"index": "a_b",
"used_range_estimates": true,
"rows": 21,
"cost": 21.14242739,
"chosen": true
},
{
"type": "scan",
"chosen": false,
"cause": "cost"
}
],
"chosen_access_method": {
"type": "ref",
"records": 21,
"cost": 21.14242739,
"uses_join_buffering": false
}
},
"rows_for_plan": 21,
"cost_for_plan": 25.34242739,
"estimated_join_cardinality": 21
}
]
},
{
"best_join_order": ["t1"]
},
{
"attaching_conditions_to_tables": {
"original_condition": "t1.a = 1 and t1.b = 2",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": null
}
]
}
},
{
"test_if_skip_sort_order": [
{
"reconsidering_access_paths_for_index_ordering": {
"clause": "ORDER BY",
"fanout": 1,
"read_time": 21.14342739,
"table": "t1",
"rows_estimation": 21,
"possible_keys": [
{
"index": "a_a",
"can_resolve_order": true,
"updated_limit": 47,
"index_scan_time": 47,
"usable": false,
"cause": "cost"
},
{
"index": "a_c",
"can_resolve_order": true,
"updated_limit": 47,
"range_scan_time": 4.331020747,
"index_scan_time": 4.331020747,
"records": 180,
"chosen": true
},
{
"index": "a_b",
"can_resolve_order": false,
"cause": "not usable index for the query"
}
]
}
},
{
"table": "t1",
"range_analysis": {
"table_scan": {
"rows": 1000,
"cost": 1.79769e308
},
"potential_range_indexes": [
{
"index": "a_a",
"usable": false,
"cause": "not applicable"
},
{
"index": "a_c",
"usable": true,
"key_parts": ["a", "c"]
},
{
"index": "a_b",
"usable": false,
"cause": "not applicable"
}
],
"setup_range_conditions": [],
"analyzing_range_alternatives": {
"range_scan_alternatives": [
{
"index": "a_c",
"ranges": ["(1) <= (a) <= (1)"],
"rowid_ordered": false,
"using_mrr": false,
"index_only": false,
"rows": 180,
"cost": 216.2943776,
"chosen": true
}
],
"analyzing_roworder_intersect": {
"cause": "too few roworder scans"
},
"analyzing_index_merge_union": []
},
"group_index_range": {
"chosen": false,
"cause": "no group by or distinct"
},
"chosen_range_access_summary": {
"range_access_plan": {
"type": "range_scan",
"index": "a_c",
"rows": 180,
"ranges": ["(1) <= (a) <= (1)"]
},
"rows_for_plan": 180,
"cost_for_plan": 216.2943776,
"chosen": true
}
}
}
]
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
drop table t1,ten,one_k;
#
# TABLE ELIMINATION
#
create table t1 (a int);
insert into t1 values (0),(1),(2),(3);
create table t0 as select * from t1;
create table t2 (a int primary key, b int)
as select a, a as b from t1 where a in (1,2);
create table t3 (a int primary key, b int)
as select a, a as b from t1 where a in (1,3);
set optimizer_trace='enabled=on';
analyze table t1;
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status OK
analyze table t2;
Table Op Msg_type Msg_text
test.t2 analyze status Engine-independent statistics collected
test.t2 analyze status OK
analyze table t3;
Table Op Msg_type Msg_text
test.t3 analyze status Engine-independent statistics collected
test.t3 analyze status OK
# table t2 should be eliminated
explain
select t1.a from t1 left join t2 on t1.a=t2.a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 4
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain
select t1.a from t1 left join t2 on t1.a=t2.a {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "select t1.a AS a from (t1 left join t2 on(t1.a = t2.a))"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
},
{
"table": "t2",
"row_may_be_null": true,
"map_bit": 1,
"depends_on_map_bits": ["0"]
}
]
},
{
"ref_optimizer_key_uses": [
{
"table": "t2",
"field": "a",
"equals": "t1.a",
"null_rejecting": true
}
]
},
{
"eliminated_tables": ["t2"]
},
{
"rows_estimation": [
{
"table": "t1",
"table_scan": {
"rows": 4,
"cost": 2.006835938
}
},
{
"table": "t2",
"rows": 1,
"cost": 1,
"table_type": "const"
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": ["t2"],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 4,
"cost": 2.006835938,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 4,
"cost": 2.006835938,
"uses_join_buffering": false
}
},
"rows_for_plan": 4,
"cost_for_plan": 2.806835937,
"estimated_join_cardinality": 4
}
]
},
{
"best_join_order": ["t2", "t1"]
},
{
"condition_on_constant_tables": "1",
"computing_condition": []
},
{
"attaching_conditions_to_tables": {
"original_condition": "1",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": null
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
# no tables should be eliminated
explain select * from t1 left join t2 on t2.a=t1.a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 4
1 SIMPLE t2 eq_ref PRIMARY PRIMARY 4 test.t1.a 1 Using where
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain select * from t1 left join t2 on t2.a=t1.a {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "select t1.a AS a,t2.a AS a,t2.b AS b from (t1 left join t2 on(t2.a = t1.a))"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
},
{
"table": "t2",
"row_may_be_null": true,
"map_bit": 1,
"depends_on_map_bits": ["0"]
}
]
},
{
"ref_optimizer_key_uses": [
{
"table": "t2",
"field": "a",
"equals": "t1.a",
"null_rejecting": true
}
]
},
{
"eliminated_tables": []
},
{
"rows_estimation": [
{
"table": "t1",
"table_scan": {
"rows": 4,
"cost": 2.006835938
}
},
{
"table": "t2",
"table_scan": {
"rows": 2,
"cost": 2.004394531
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 4,
"cost": 2.006835938,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 4,
"cost": 2.006835938,
"uses_join_buffering": false
}
},
"rows_for_plan": 4,
"cost_for_plan": 2.806835937,
"rest_of_plan": [
{
"plan_prefix": ["t1"],
"table": "t2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "eq_ref",
"index": "PRIMARY",
"rows": 1,
"cost": 4,
"chosen": true
},
{
"access_type": "scan",
"resulting_rows": 2,
"cost": 8.017578125,
"chosen": false
}
],
"chosen_access_method": {
"type": "eq_ref",
"records": 1,
"cost": 4,
"uses_join_buffering": false
}
},
"rows_for_plan": 4,
"cost_for_plan": 7.606835937,
"estimated_join_cardinality": 4
}
]
}
]
},
{
"best_join_order": ["t1", "t2"]
},
{
"condition_on_constant_tables": "1",
"computing_condition": []
},
{
"attaching_conditions_to_tables": {
"original_condition": "1",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": null
},
{
"table": "t2",
"attached": "trigcond(trigcond(t1.a is not null))"
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
# multiple tables are eliminated
explain select t1.a from t1 left join (t2 join t3 on t2.b=t3.b) on t2.a=t1.a and t3.a=t1.a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 4
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain select t1.a from t1 left join (t2 join t3 on t2.b=t3.b) on t2.a=t1.a and t3.a=t1.a {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "select t1.a AS a from (t1 left join (t2 join t3 on(t2.b = t3.b)) on(t2.a = t1.a and t3.a = t1.a))"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
},
{
"table": "t2",
"row_may_be_null": true,
"map_bit": 1,
"depends_on_map_bits": ["0"]
},
{
"table": "t3",
"row_may_be_null": true,
"map_bit": 2,
"depends_on_map_bits": ["0"]
}
]
},
{
"ref_optimizer_key_uses": [
{
"table": "t2",
"field": "a",
"equals": "t1.a",
"null_rejecting": true
},
{
"table": "t2",
"field": "a",
"equals": "t3.a",
"null_rejecting": true
},
{
"table": "t3",
"field": "a",
"equals": "t2.a",
"null_rejecting": true
},
{
"table": "t3",
"field": "a",
"equals": "t1.a",
"null_rejecting": true
}
]
},
{
"eliminated_tables": ["t3", "t2"]
},
{
"rows_estimation": [
{
"table": "t1",
"table_scan": {
"rows": 4,
"cost": 2.006835938
}
},
{
"table": "t2",
"rows": 1,
"cost": 1,
"table_type": "const"
},
{
"table": "t3",
"rows": 1,
"cost": 1,
"table_type": "const"
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": ["t3", "t2"],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 4,
"cost": 2.006835938,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 4,
"cost": 2.006835938,
"uses_join_buffering": false
}
},
"rows_for_plan": 4,
"cost_for_plan": 2.806835937,
"estimated_join_cardinality": 4
}
]
},
{
"best_join_order": ["t3", "t2", "t1"]
},
{
"condition_on_constant_tables": "1",
"computing_condition": []
},
{
"attaching_conditions_to_tables": {
"original_condition": "1",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": null
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
drop table t0, t1, t2, t3;
#
# IN subquery to sem-join is traced
#
create table t0 (a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t1(a int, b int);
insert into t1 values (0,0),(1,1),(2,2);
create table t2 as select * from t1;
create table t11(a int, b int);
create table t10 (pk int, a int);
insert into t10 select a,a from t0;
create table t12 like t10;
insert into t12 select * from t10;
analyze table t1,t10;
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status OK
test.t10 analyze status Engine-independent statistics collected
test.t10 analyze status OK
set optimizer_trace='enabled=on';
explain extended select * from t1 where a in (select pk from t10);
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 3 100.00
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 4 func 1 100.00
2 MATERIALIZED t10 ALL NULL NULL NULL NULL 10 100.00
Warnings:
Note 1003 select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` semi join (`test`.`t10`) where 1
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain extended select * from t1 where a in (select pk from t10) {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"join_preparation": {
"select_id": 2,
"steps": [
{
"transformation": {
"select_id": 2,
"from": "IN (SELECT)",
"to": "materialization",
"sjm_scan_allowed": true,
"possible": true
}
},
{
"transformation": {
"select_id": 2,
"from": "IN (SELECT)",
"to": "semijoin",
"chosen": true
}
},
{
"expanded_query": "/* select#2 */ select t10.pk from t10"
}
]
}
},
{
"expanded_query": "/* select#1 */ select t1.a AS a,t1.b AS b from t1 where t1.a in (/* select#2 */ select t10.pk from t10)"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"transformation": {
"select_id": 2,
"from": "IN (SELECT)",
"to": "semijoin",
"converted_to_semi_join": true
}
},
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "1 and t1.a = t10.pk",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "1 and multiple equal(t1.a, t10.pk)"
},
{
"transformation": "constant_propagation",
"resulting_condition": "1 and multiple equal(t1.a, t10.pk)"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "multiple equal(t1.a, t10.pk)"
}
]
}
},
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
},
{
"table": "t10",
"row_may_be_null": false,
"map_bit": 1,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": []
},
{
"rows_estimation": [
{
"table": "t1",
"table_scan": {
"rows": 3,
"cost": 2.006591797
}
},
{
"table": "t10",
"table_scan": {
"rows": 10,
"cost": 2.021972656
}
}
]
},
{
"semijoin_table_pullout": {
"pulled_out_tables": []
}
},
{
"execution_plan_for_potential_materialization": {
"steps": [
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t10",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 10,
"cost": 2.021972656,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 10,
"cost": 2.021972656,
"uses_join_buffering": false
}
},
"rows_for_plan": 10,
"cost_for_plan": 4.021972656,
"estimated_join_cardinality": 10
}
]
}
]
}
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.006591797,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.006591797,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 2.606591797,
"semijoin_strategy_choice": [],
"rest_of_plan": [
{
"plan_prefix": ["t1"],
"table": "t10",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 10,
"cost": 2.021972656,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 10,
"cost": 2.021972656,
"uses_join_buffering": true
}
},
"rows_for_plan": 30,
"cost_for_plan": 10.62856445,
"semijoin_strategy_choice": [
{
"strategy": "FirstMatch",
"records": 3,
"read_time": 10.62856445
},
{
"strategy": "SJ-Materialization",
"records": 3,
"read_time": 5.278564453
},
{
"strategy": "DuplicateWeedout",
"records": 3,
"read_time": 27.12856445
},
{
"chosen_strategy": "SJ-Materialization"
}
],
"estimated_join_cardinality": 3
}
]
},
{
"plan_prefix": [],
"table": "t10",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 10,
"cost": 2.021972656,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 10,
"cost": 2.021972656,
"uses_join_buffering": false
}
},
"rows_for_plan": 10,
"cost_for_plan": 4.021972656,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
}
]
},
{
"fix_semijoin_strategies_for_picked_join_order": [
{
"semi_join_strategy": "SJ-Materialization",
"join_order": [
{
"table": "t10"
}
]
}
]
},
{
"best_join_order": ["t1", "<subquery2>"]
},
{
"condition_on_constant_tables": "1",
"computing_condition": []
},
{
"attaching_conditions_to_tables": {
"original_condition": "1",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": null
},
{
"table": "t10",
"attached": null
},
{
"table": "<subquery2>",
"attached": null
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
drop table t0,t1,t11,t10,t12,t2;
#
# Selectivities for columns and indexes.
#
create table t0 (a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t1 (
pk int,
a int,
b int,
key pk(pk),
key pk_a(pk,a),
key pk_a_b(pk,a,b));
insert into t1 select a,a,a from t0;
ANALYZE TABLE t1 PERSISTENT FOR COLUMNS (a,b) INDEXES ();
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status Table is already up to date
set @save_optimizer_use_condition_selectivity=@@optimizer_use_condition_selectivity;
set @save_use_stat_tables= @@use_stat_tables;
set @@optimizer_use_condition_selectivity=4;
set @@use_stat_tables= PREFERABLY;
set optimizer_trace='enabled=on';
explain select * from t1 where pk = 2 and a=5 and b=1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref pk,pk_a,pk_a_b pk_a_b 15 const,const,const 1 Using index
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain select * from t1 where pk = 2 and a=5 and b=1 {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "select t1.pk AS pk,t1.a AS a,t1.b AS b from t1 where t1.pk = 2 and t1.a = 5 and t1.b = 1"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "t1.pk = 2 and t1.a = 5 and t1.b = 1",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "multiple equal(2, t1.pk) and multiple equal(5, t1.a) and multiple equal(1, t1.b)"
},
{
"transformation": "constant_propagation",
"resulting_condition": "multiple equal(2, t1.pk) and multiple equal(5, t1.a) and multiple equal(1, t1.b)"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "multiple equal(2, t1.pk) and multiple equal(5, t1.a) and multiple equal(1, t1.b)"
}
]
}
},
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": [
{
"table": "t1",
"field": "pk",
"equals": "2",
"null_rejecting": true
},
{
"table": "t1",
"field": "pk",
"equals": "2",
"null_rejecting": true
},
{
"table": "t1",
"field": "a",
"equals": "5",
"null_rejecting": true
},
{
"table": "t1",
"field": "pk",
"equals": "2",
"null_rejecting": true
},
{
"table": "t1",
"field": "a",
"equals": "5",
"null_rejecting": true
},
{
"table": "t1",
"field": "b",
"equals": "1",
"null_rejecting": true
}
]
},
{
"rows_estimation": [
{
"table": "t1",
"range_analysis": {
"table_scan": {
"rows": 10,
"cost": 6.031738281
},
"potential_range_indexes": [
{
"index": "pk",
"usable": true,
"key_parts": ["pk"]
},
{
"index": "pk_a",
"usable": true,
"key_parts": ["pk", "a"]
},
{
"index": "pk_a_b",
"usable": true,
"key_parts": ["pk", "a", "b"]
}
],
"best_covering_index_scan": {
"index": "pk_a_b",
"cost": 3.010739566,
"chosen": true
},
"setup_range_conditions": [],
"analyzing_range_alternatives": {
"range_scan_alternatives": [
{
"index": "pk",
"ranges": ["(2) <= (pk) <= (2)"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": false,
"rows": 1,
"cost": 1.345585794,
"chosen": true
},
{
"index": "pk_a",
"ranges": ["(2,5) <= (pk,a) <= (2,5)"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": false,
"rows": 1,
"cost": 1.345829876,
"chosen": false,
"cause": "cost"
},
{
"index": "pk_a_b",
"ranges": ["(2,5,1) <= (pk,a,b) <= (2,5,1)"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": true,
"rows": 1,
"cost": 0.346073957,
"chosen": true
}
],
"analyzing_roworder_intersect": {
"intersecting_indexes": [
{
"index": "pk",
"index_scan_cost": 1.000585794,
"cumulated_index_scan_cost": 1.000585794,
"disk_sweep_cost": 0.90078125,
"cumulative_total_cost": 1.901367044,
"usable": true,
"matching_rows_now": 1,
"intersect_covering_with_this_index": false,
"chosen": true
},
{
"index": "pk_a",
"usable": false,
"cause": "does not reduce cost of intersect"
},
{
"index": "pk_a_b",
"usable": false,
"cause": "does not reduce cost of intersect"
}
],
"clustered_pk": {
"clustered_pk_added_to_intersect": false,
"cause": "no clustered pk index"
},
"chosen": false,
"cause": "cost"
},
"analyzing_index_merge_union": []
},
"group_index_range": {
"chosen": false,
"cause": "no group by or distinct"
},
"chosen_range_access_summary": {
"range_access_plan": {
"type": "range_scan",
"index": "pk_a_b",
"rows": 1,
"ranges": ["(2,5,1) <= (pk,a,b) <= (2,5,1)"]
},
"rows_for_plan": 1,
"cost_for_plan": 0.346073957,
"chosen": true
}
}
},
{
"table": "t1",
"rowid_filters": [
{
"key": "pk",
"build_cost": 0.130585794,
"rows": 1
},
{
"key": "pk_a",
"build_cost": 0.130829876,
"rows": 1
},
{
"key": "pk_a_b",
"build_cost": 0.131073957,
"rows": 1
}
]
},
{
"selectivity_for_indexes": [
{
"index_name": "pk_a_b",
"selectivity_from_index": 0.1
}
],
"selectivity_for_columns": [
{
"column_name": "a",
"ranges": ["5 <= a <= 5"],
"selectivity_from_histogram": 0.1
},
{
"column_name": "b",
"ranges": ["1 <= b <= 1"],
"selectivity_from_histogram": 0.1
}
],
"cond_selectivity": 0.1
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "ref",
"index": "pk",
"used_range_estimates": true,
"rows": 1,
"cost": 1.125585794,
"chosen": true
},
{
"access_type": "ref",
"index": "pk_a",
"used_range_estimates": true,
"rows": 1,
"cost": 1.125829876,
"chosen": false,
"cause": "cost"
},
{
"access_type": "ref",
"index": "pk_a_b",
"used_range_estimates": true,
"rows": 1,
"cost": 0.126073957,
"chosen": true
},
{
"type": "scan",
"chosen": false,
"cause": "cost"
}
],
"chosen_access_method": {
"type": "ref",
"records": 1,
"cost": 0.126073957,
"uses_join_buffering": false
}
},
"rows_for_plan": 1,
"cost_for_plan": 0.326073957,
"estimated_join_cardinality": 1
}
]
},
{
"best_join_order": ["t1"]
},
{
"attaching_conditions_to_tables": {
"original_condition": "t1.pk = 2 and t1.a = 5 and t1.b = 1",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": null
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
set @@optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
set @@use_stat_tables= @save_use_stat_tables;
drop table t0,t1;
set optimizer_trace="enabled=off";
#
# Tests added to show that sub-statements are not traced
#
create table t1(a int);
insert into t1 values (1),(2),(3),(4);
create table t2(a int);
insert into t2 values (1),(2),(3),(4);
create function f1(a int) returns int
begin
declare a int default 0;
set a= a+ (select count(*) from t2);
return a;
end|
create function f2(a int) returns int
begin
declare a int default 0;
select count(*) from t2 into a;
return a;
end|
Warnings:
Warning 1287 '<select expression> INTO <destination>;' is deprecated and will be removed in a future release. Please use 'SELECT <select list> INTO <destination> FROM...' instead
set optimizer_trace='enabled=on';
select f1(a) from t1;
f1(a)
4
4
4
4
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
select f1(a) from t1 {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "select f1(t1.a) AS `f1(a)` from t1"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"rows_estimation": [
{
"table": "t1",
"table_scan": {
"rows": 4,
"cost": 2.006835938
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 4,
"cost": 2.006835938,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 4,
"cost": 2.006835938,
"uses_join_buffering": false
}
},
"rows_for_plan": 4,
"cost_for_plan": 2.806835937,
"estimated_join_cardinality": 4
}
]
},
{
"best_join_order": ["t1"]
},
{
"attaching_conditions_to_tables": {
"original_condition": null,
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": null
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
select f2(a) from t1;
f2(a)
4
4
4
4
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
select f2(a) from t1 {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "select f2(t1.a) AS `f2(a)` from t1"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"rows_estimation": [
{
"table": "t1",
"table_scan": {
"rows": 4,
"cost": 2.006835938
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 4,
"cost": 2.006835938,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 4,
"cost": 2.006835938,
"uses_join_buffering": false
}
},
"rows_for_plan": 4,
"cost_for_plan": 2.806835937,
"estimated_join_cardinality": 4
}
]
},
{
"best_join_order": ["t1"]
},
{
"attaching_conditions_to_tables": {
"original_condition": null,
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": null
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
drop table t1,t2;
drop function f1;
drop function f2;
set optimizer_trace='enabled=off';
#
# MDEV-18489: Limit the memory used by the optimizer trace
#
create table t1 (a int);
insert into t1 values (1),(2);
set optimizer_trace='enabled=on';
set @save_optimizer_trace_max_mem_size= @@optimizer_trace_max_mem_size;
select * from t1;
a
1
2
select length(trace) from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
length(trace)
2183
set optimizer_trace_max_mem_size=100;
select * from t1;
a
1
2
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
select * from t1 {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
2083 0
set optimizer_trace_max_mem_size=0;
select * from t1;
a
1
2
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
select * from t1 2183 0
drop table t1;
set optimizer_trace='enabled=off';
set @@optimizer_trace_max_mem_size= @save_optimizer_trace_max_mem_size;
#
# MDEV-18527: Optimizer trace for DELETE query shows table:null
#
create table ten(a int);
insert into ten values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t0 (a int, b int);
insert into t0 select a,a from ten;
alter table t0 add key(a);
set optimizer_trace=1;
explain delete from t0 where t0.a<3;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t0 range a a 5 NULL 3 Using where
select * from information_schema.optimizer_trace;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain delete from t0 where t0.a<3 {
"steps": [
{
"table": "t0",
"range_analysis": {
"table_scan": {
"rows": 10,
"cost": 6.021972656
},
"potential_range_indexes": [
{
"index": "a",
"usable": true,
"key_parts": ["a"]
}
],
"setup_range_conditions": [],
"analyzing_range_alternatives": {
"range_scan_alternatives": [
{
"index": "a",
"ranges": ["(NULL) < (a) < (3)"],
"rowid_ordered": false,
"using_mrr": false,
"index_only": false,
"rows": 3,
"cost": 3.746757383,
"chosen": true
}
],
"analyzing_index_merge_union": []
},
"group_index_range": {
"chosen": false,
"cause": "no join"
},
"chosen_range_access_summary": {
"range_access_plan": {
"type": "range_scan",
"index": "a",
"rows": 3,
"ranges": ["(NULL) < (a) < (3)"]
},
"rows_for_plan": 3,
"cost_for_plan": 3.746757383,
"chosen": true
}
}
}
]
} 0 0
drop table ten,t0;
set optimizer_trace='enabled=off';
#
# MDEV-18528: Optimizer trace support for multi-table UPDATE and DELETE
#
set optimizer_trace=1;
create table ten(a int);
insert into ten values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t0 (a int, b int);
insert into t0 select a,a from ten;
alter table t0 add key(a);
create table t1 like t0;
insert into t1 select * from t0;
explain delete t0,t1 from t0, t1 where t0.a=t1.a and t1.a<3;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t0 range a a 5 NULL 3 Using where
1 SIMPLE t1 ref a a 5 test.t0.a 1
select * from information_schema.optimizer_trace;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain delete t0,t1 from t0, t1 where t0.a=t1.a and t1.a<3 {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "delete from t0,t1 using t0 join t1 where t0.a = t1.a and t1.a < 3"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "t0.a = t1.a and t1.a < 3",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "t1.a < 3 and multiple equal(t0.a, t1.a)"
},
{
"transformation": "constant_propagation",
"resulting_condition": "t1.a < 3 and multiple equal(t0.a, t1.a)"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "t1.a < 3 and multiple equal(t0.a, t1.a)"
}
]
}
},
{
"table_dependencies": [
{
"table": "t0",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
},
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 1,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": [
{
"table": "t0",
"field": "a",
"equals": "t1.a",
"null_rejecting": true
},
{
"table": "t1",
"field": "a",
"equals": "t0.a",
"null_rejecting": true
}
]
},
{
"rows_estimation": [
{
"table": "t0",
"range_analysis": {
"table_scan": {
"rows": 10,
"cost": 6.021972656
},
"potential_range_indexes": [
{
"index": "a",
"usable": true,
"key_parts": ["a"]
}
],
"best_covering_index_scan": {
"index": "a",
"cost": 3.005857945,
"chosen": true
},
"setup_range_conditions": [],
"analyzing_range_alternatives": {
"range_scan_alternatives": [
{
"index": "a",
"ranges": ["(NULL) < (a) < (3)"],
"rowid_ordered": false,
"using_mrr": false,
"index_only": true,
"rows": 3,
"cost": 0.746757383,
"chosen": true
}
],
"analyzing_roworder_intersect": {
"cause": "too few roworder scans"
},
"analyzing_index_merge_union": []
},
"group_index_range": {
"chosen": false,
"cause": "not single_table"
},
"chosen_range_access_summary": {
"range_access_plan": {
"type": "range_scan",
"index": "a",
"rows": 3,
"ranges": ["(NULL) < (a) < (3)"]
},
"rows_for_plan": 3,
"cost_for_plan": 0.746757383,
"chosen": true
}
}
},
{
"selectivity_for_indexes": [
{
"index_name": "a",
"selectivity_from_index": 0.3
}
],
"selectivity_for_columns": [],
"cond_selectivity": 0.3
},
{
"table": "t1",
"range_analysis": {
"table_scan": {
"rows": 10,
"cost": 6.021972656
},
"potential_range_indexes": [
{
"index": "a",
"usable": true,
"key_parts": ["a"]
}
],
"best_covering_index_scan": {
"index": "a",
"cost": 3.005857945,
"chosen": true
},
"setup_range_conditions": [],
"analyzing_range_alternatives": {
"range_scan_alternatives": [
{
"index": "a",
"ranges": ["(NULL) < (a) < (3)"],
"rowid_ordered": false,
"using_mrr": false,
"index_only": true,
"rows": 3,
"cost": 0.746757383,
"chosen": true
}
],
"analyzing_roworder_intersect": {
"cause": "too few roworder scans"
},
"analyzing_index_merge_union": []
},
"group_index_range": {
"chosen": false,
"cause": "not single_table"
},
"chosen_range_access_summary": {
"range_access_plan": {
"type": "range_scan",
"index": "a",
"rows": 3,
"ranges": ["(NULL) < (a) < (3)"]
},
"rows_for_plan": 3,
"cost_for_plan": 0.746757383,
"chosen": true
}
}
},
{
"selectivity_for_indexes": [
{
"index_name": "a",
"selectivity_from_index": 0.3
}
],
"selectivity_for_columns": [],
"cond_selectivity": 0.3
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t0",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "range",
"resulting_rows": 3,
"cost": 0.746757383,
"chosen": true
}
],
"chosen_access_method": {
"type": "range",
"records": 3,
"cost": 0.746757383,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 1.346757383,
"rest_of_plan": [
{
"plan_prefix": ["t0"],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "ref",
"index": "a",
"used_range_estimates": false,
"cause": "not better than ref estimates",
"rows": 1,
"cost": 3.001757383,
"chosen": true
},
{
"type": "scan",
"chosen": false,
"cause": "cost"
}
],
"chosen_access_method": {
"type": "ref",
"records": 1,
"cost": 3.001757383,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 4.948514767,
"estimated_join_cardinality": 3
}
]
},
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "range",
"resulting_rows": 3,
"cost": 0.746757383,
"chosen": true
}
],
"chosen_access_method": {
"type": "range",
"records": 3,
"cost": 0.746757383,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 1.346757383,
"rest_of_plan": [
{
"plan_prefix": ["t1"],
"table": "t0",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "ref",
"index": "a",
"used_range_estimates": false,
"cause": "not better than ref estimates",
"rowid_filter_skipped": "worst/max seeks clipping",
"rows": 2,
"cost": 3.003514767,
"chosen": true
},
{
"type": "scan",
"chosen": false,
"cause": "cost"
}
],
"chosen_access_method": {
"type": "ref",
"records": 2,
"cost": 3.003514767,
"uses_join_buffering": false
}
},
"rows_for_plan": 6,
"cost_for_plan": 5.55027215,
"pruned_by_cost": true
}
]
}
]
},
{
"best_join_order": ["t0", "t1"]
},
{
"attaching_conditions_to_tables": {
"original_condition": "t1.a = t0.a and t0.a < 3",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t0",
"attached": "t0.a < 3 and t0.a is not null"
},
{
"table": "t1",
"attached": null
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
drop table ten,t0,t1;
set optimizer_trace='enabled=off';
#
# Merged to Materialized for derived tables
#
set optimizer_trace=1;
create table t1 (a int);
insert into t1 values (1),(2),(3);
explain select * from (select rand() from t1)q;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 3
2 DERIVED t1 ALL NULL NULL NULL NULL 3
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain select * from (select rand() from t1)q {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"derived": {
"table": "q",
"select_id": 2,
"algorithm": "materialized"
}
},
{
"join_preparation": {
"select_id": 2,
"steps": [
{
"expanded_query": "/* select#2 */ select rand() AS `rand()` from t1"
}
]
}
},
{
"expanded_query": "/* select#1 */ select q.`rand()` AS `rand()` from (/* select#2 */ select rand() AS `rand()` from t1) q"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"join_optimization": {
"select_id": 2,
"steps": [
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"rows_estimation": [
{
"table": "t1",
"table_scan": {
"rows": 3,
"cost": 2.005126953
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 2.605126953,
"estimated_join_cardinality": 3
}
]
},
{
"best_join_order": ["t1"]
},
{
"attaching_conditions_to_tables": {
"original_condition": null,
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": null
}
]
}
}
]
}
},
{
"table_dependencies": [
{
"table": "<derived2>",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"rows_estimation": [
{
"table": "<derived2>",
"table_scan": {
"rows": 3,
"cost": 3
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "<derived2>",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 3,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 3,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 3.6,
"estimated_join_cardinality": 3
}
]
},
{
"best_join_order": ["<derived2>"]
},
{
"attaching_conditions_to_tables": {
"original_condition": null,
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "<derived2>",
"attached": null
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": [
{
"join_execution": {
"select_id": 2,
"steps": []
}
}
]
}
}
]
} 0 0
drop table t1;
set optimizer_trace='enabled=off';
#
# Semi-join nest
#
set optimizer_trace=1;
create table t1 (a int);
insert into t1 values (1),(2),(3);
create table t2(a int);
insert into t2 values (1),(2),(3),(1),(2),(3),(1),(2),(3);
set @save_optimizer_switch= @@optimizer_switch;
explain select * from t1 where a in (select t_inner_1.a from t1 t_inner_1, t1 t_inner_2);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 3
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 4 func 1
2 MATERIALIZED t_inner_1 ALL NULL NULL NULL NULL 3
2 MATERIALIZED t_inner_2 ALL NULL NULL NULL NULL 3 Using join buffer (flat, BNL join)
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain select * from t1 where a in (select t_inner_1.a from t1 t_inner_1, t1 t_inner_2) {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"join_preparation": {
"select_id": 2,
"steps": [
{
"transformation": {
"select_id": 2,
"from": "IN (SELECT)",
"to": "materialization",
"sjm_scan_allowed": true,
"possible": true
}
},
{
"transformation": {
"select_id": 2,
"from": "IN (SELECT)",
"to": "semijoin",
"chosen": true
}
},
{
"expanded_query": "/* select#2 */ select t_inner_1.a from t1 t_inner_1 join t1 t_inner_2"
}
]
}
},
{
"expanded_query": "/* select#1 */ select t1.a AS a from t1 where t1.a in (/* select#2 */ select t_inner_1.a from t1 t_inner_1 join t1 t_inner_2)"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"transformation": {
"select_id": 2,
"from": "IN (SELECT)",
"to": "semijoin",
"converted_to_semi_join": true
}
},
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "1 and t1.a = t_inner_1.a",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "1 and multiple equal(t1.a, t_inner_1.a)"
},
{
"transformation": "constant_propagation",
"resulting_condition": "1 and multiple equal(t1.a, t_inner_1.a)"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "multiple equal(t1.a, t_inner_1.a)"
}
]
}
},
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
},
{
"table": "t_inner_1",
"row_may_be_null": false,
"map_bit": 1,
"depends_on_map_bits": []
},
{
"table": "t_inner_2",
"row_may_be_null": false,
"map_bit": 2,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": []
},
{
"rows_estimation": [
{
"table": "t1",
"table_scan": {
"rows": 3,
"cost": 2.005126953
}
},
{
"table": "t_inner_1",
"table_scan": {
"rows": 3,
"cost": 2.005126953
}
},
{
"table": "t_inner_2",
"table_scan": {
"rows": 3,
"cost": 2.005126953
}
}
]
},
{
"semijoin_table_pullout": {
"pulled_out_tables": []
}
},
{
"execution_plan_for_potential_materialization": {
"steps": [
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t_inner_1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 2.605126953,
"rest_of_plan": [
{
"plan_prefix": ["t_inner_1"],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": true
}
},
"rows_for_plan": 9,
"cost_for_plan": 6.410253906,
"estimated_join_cardinality": 9
}
]
},
{
"plan_prefix": [],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 2.605126953,
"pruned_by_heuristic": true
}
]
}
]
}
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 2.605126953,
"semijoin_strategy_choice": [],
"rest_of_plan": [
{
"plan_prefix": ["t1"],
"table": "t_inner_1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": true
}
},
"rows_for_plan": 9,
"cost_for_plan": 6.410253906,
"semijoin_strategy_choice": [],
"rest_of_plan": [
{
"plan_prefix": ["t1", "t_inner_1"],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": true
}
},
"rows_for_plan": 27,
"cost_for_plan": 13.81538086,
"semijoin_strategy_choice": [
{
"strategy": "FirstMatch",
"records": 3,
"read_time": 33.86665039
},
{
"strategy": "SJ-Materialization",
"records": 3,
"read_time": 7.215380859
},
{
"strategy": "DuplicateWeedout",
"records": 3,
"read_time": 18.31538086
},
{
"chosen_strategy": "SJ-Materialization"
}
],
"estimated_join_cardinality": 3
}
]
},
{
"plan_prefix": ["t1"],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": true
}
},
"rows_for_plan": 9,
"cost_for_plan": 6.410253906,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
}
]
},
{
"plan_prefix": [],
"table": "t_inner_1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 2.605126953,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 2.605126953,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
}
]
},
{
"fix_semijoin_strategies_for_picked_join_order": [
{
"semi_join_strategy": "SJ-Materialization",
"join_order": [
{
"table": "t_inner_1"
},
{
"table": "t_inner_2"
}
]
}
]
},
{
"best_join_order": ["t1", "<subquery2>"]
},
{
"condition_on_constant_tables": "1",
"computing_condition": []
},
{
"attaching_conditions_to_tables": {
"original_condition": "1",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": null
},
{
"table": "t_inner_1",
"attached": null
},
{
"table": "t_inner_2",
"attached": null
},
{
"table": "<subquery2>",
"attached": null
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
# with Firstmatch, mostly for tracing fix_semijoin_strategies_for_picked_join_order
set optimizer_switch='materialization=off';
explain select * from t1 t_outer_1,t2 t_outer_2 where t_outer_1.a in (select t_inner_1.a from t2 t_inner_2, t1 t_inner_1) and
t_outer_2.a in (select t_inner_3.a from t2 t_inner_3, t1 t_inner_4);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t_outer_1 ALL NULL NULL NULL NULL 3
1 PRIMARY t_inner_1 ALL NULL NULL NULL NULL 3 Using where; Start temporary; Using join buffer (flat, BNL join)
1 PRIMARY t_inner_2 ALL NULL NULL NULL NULL 9 End temporary; Using join buffer (incremental, BNL join)
1 PRIMARY t_inner_4 ALL NULL NULL NULL NULL 3 Start temporary; Using join buffer (incremental, BNL join)
1 PRIMARY t_outer_2 ALL NULL NULL NULL NULL 9 Using join buffer (incremental, BNL join)
1 PRIMARY t_inner_3 ALL NULL NULL NULL NULL 9 Using where; End temporary; Using join buffer (incremental, BNL join)
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain select * from t1 t_outer_1,t2 t_outer_2 where t_outer_1.a in (select t_inner_1.a from t2 t_inner_2, t1 t_inner_1) and
t_outer_2.a in (select t_inner_3.a from t2 t_inner_3, t1 t_inner_4) {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"join_preparation": {
"select_id": 2,
"steps": [
{
"transformation": {
"select_id": 2,
"from": "IN (SELECT)",
"to": "materialization",
"sjm_scan_allowed": true,
"possible": true
}
},
{
"transformation": {
"select_id": 2,
"from": "IN (SELECT)",
"to": "semijoin",
"chosen": true
}
},
{
"expanded_query": "/* select#2 */ select t_inner_1.a from t2 t_inner_2 join t1 t_inner_1"
}
]
}
},
{
"join_preparation": {
"select_id": 3,
"steps": [
{
"transformation": {
"select_id": 3,
"from": "IN (SELECT)",
"to": "materialization",
"sjm_scan_allowed": true,
"possible": true
}
},
{
"transformation": {
"select_id": 3,
"from": "IN (SELECT)",
"to": "semijoin",
"chosen": true
}
},
{
"expanded_query": "/* select#3 */ select t_inner_3.a from t2 t_inner_3 join t1 t_inner_4"
}
]
}
},
{
"expanded_query": "/* select#1 */ select t_outer_1.a AS a,t_outer_2.a AS a from t1 t_outer_1 join t2 t_outer_2 where t_outer_1.a in (/* select#2 */ select t_inner_1.a from t2 t_inner_2 join t1 t_inner_1) and t_outer_2.a in (/* select#3 */ select t_inner_3.a from t2 t_inner_3 join t1 t_inner_4)"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"transformation": {
"select_id": 2,
"from": "IN (SELECT)",
"to": "semijoin",
"converted_to_semi_join": true
}
},
{
"transformation": {
"select_id": 3,
"from": "IN (SELECT)",
"to": "semijoin",
"converted_to_semi_join": true
}
},
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "1 and 1 and t_outer_1.a = t_inner_1.a and t_outer_2.a = t_inner_3.a",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "1 and 1 and multiple equal(t_outer_1.a, t_inner_1.a) and multiple equal(t_outer_2.a, t_inner_3.a)"
},
{
"transformation": "constant_propagation",
"resulting_condition": "1 and 1 and multiple equal(t_outer_1.a, t_inner_1.a) and multiple equal(t_outer_2.a, t_inner_3.a)"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "multiple equal(t_outer_1.a, t_inner_1.a) and multiple equal(t_outer_2.a, t_inner_3.a)"
}
]
}
},
{
"table_dependencies": [
{
"table": "t_outer_1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
},
{
"table": "t_outer_2",
"row_may_be_null": false,
"map_bit": 1,
"depends_on_map_bits": []
},
{
"table": "t_inner_2",
"row_may_be_null": false,
"map_bit": 2,
"depends_on_map_bits": []
},
{
"table": "t_inner_1",
"row_may_be_null": false,
"map_bit": 3,
"depends_on_map_bits": []
},
{
"table": "t_inner_3",
"row_may_be_null": false,
"map_bit": 4,
"depends_on_map_bits": []
},
{
"table": "t_inner_4",
"row_may_be_null": false,
"map_bit": 5,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": []
},
{
"rows_estimation": [
{
"table": "t_outer_1",
"table_scan": {
"rows": 3,
"cost": 2.005126953
}
},
{
"table": "t_outer_2",
"table_scan": {
"rows": 9,
"cost": 2.015380859
}
},
{
"table": "t_inner_2",
"table_scan": {
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"uses_join_buffering": true
}
},
"rows_for_plan": 6561,
"cost_for_plan": 1486.656396,
"semijoin_strategy_choice": [],
"pruned_by_cost": true
}
]
},
{
"plan_prefix": ["t_outer_1", "t_inner_1", "t_inner_3"],
"table": "t_inner_4",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": true
}
},
"rows_for_plan": 243,
"cost_for_plan": 75.23076172,
"semijoin_strategy_choice": [],
"rest_of_plan": [
{
"plan_prefix": [
"t_outer_1",
"t_inner_1",
"t_inner_3",
"t_inner_4"
],
"table": "t_outer_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 2187,
"cost_for_plan": 514.6461426,
"semijoin_strategy_choice": [],
"pruned_by_cost": true
},
{
"plan_prefix": [
"t_outer_1",
"t_inner_1",
"t_inner_3",
"t_inner_4"
],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 2187,
"cost_for_plan": 514.6461426,
"semijoin_strategy_choice": [],
"pruned_by_cost": true
}
]
},
{
"plan_prefix": ["t_outer_1", "t_inner_1", "t_inner_3"],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 729,
"cost_for_plan": 172.4410156,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
}
]
}
]
},
{
"plan_prefix": ["t_outer_1"],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 27,
"cost_for_plan": 10.02050781,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": ["t_outer_1"],
"table": "t_outer_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 27,
"cost_for_plan": 10.02050781,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": ["t_outer_1"],
"table": "t_inner_4",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": true
}
},
"rows_for_plan": 9,
"cost_for_plan": 6.410253906,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": ["t_outer_1"],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 27,
"cost_for_plan": 10.02050781,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
}
]
},
{
"plan_prefix": [],
"table": "t_inner_1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 2.605126953,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": false
}
},
"rows_for_plan": 9,
"cost_for_plan": 3.815380859,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_outer_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": false
}
},
"rows_for_plan": 9,
"cost_for_plan": 3.815380859,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_inner_4",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 2.605126953,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": false
}
},
"rows_for_plan": 9,
"cost_for_plan": 3.815380859,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
}
]
},
{
"fix_semijoin_strategies_for_picked_join_order": [
{
"semi_join_strategy": "DuplicateWeedout"
},
{
"semi_join_strategy": "DuplicateWeedout"
}
]
},
{
"best_join_order": [
"t_outer_1",
"t_inner_1",
"t_inner_2",
"t_inner_4",
"t_outer_2",
"t_inner_3"
]
},
{
"attaching_conditions_to_tables": {
"original_condition": "t_inner_1.a = t_outer_1.a and t_inner_3.a = t_outer_2.a",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t_outer_1",
"attached": null
},
{
"table": "t_inner_1",
"attached": "t_inner_1.a = t_outer_1.a"
},
{
"table": "t_inner_2",
"attached": null
},
{
"table": "t_inner_4",
"attached": null
},
{
"table": "t_outer_2",
"attached": null
},
{
"table": "t_inner_3",
"attached": "t_inner_3.a = t_outer_2.a"
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
set optimizer_switch='materialization=on';
explain select * from t1 t_outer_1,t2 t_outer_2 where t_outer_1.a in (select t_inner_1.a from t2 t_inner_2, t1 t_inner_1) and
t_outer_2.a in (select t_inner_3.a from t2 t_inner_3, t1 t_inner_4);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t_outer_1 ALL NULL NULL NULL NULL 3
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 4 func 1
1 PRIMARY t_outer_2 ALL NULL NULL NULL NULL 9 Using join buffer (flat, BNL join)
1 PRIMARY <subquery3> eq_ref distinct_key distinct_key 4 func 1
2 MATERIALIZED t_inner_1 ALL NULL NULL NULL NULL 3
2 MATERIALIZED t_inner_2 ALL NULL NULL NULL NULL 9 Using join buffer (flat, BNL join)
3 MATERIALIZED t_inner_4 ALL NULL NULL NULL NULL 3
3 MATERIALIZED t_inner_3 ALL NULL NULL NULL NULL 9 Using join buffer (flat, BNL join)
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain select * from t1 t_outer_1,t2 t_outer_2 where t_outer_1.a in (select t_inner_1.a from t2 t_inner_2, t1 t_inner_1) and
t_outer_2.a in (select t_inner_3.a from t2 t_inner_3, t1 t_inner_4) {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"join_preparation": {
"select_id": 2,
"steps": [
{
"transformation": {
"select_id": 2,
"from": "IN (SELECT)",
"to": "materialization",
"sjm_scan_allowed": true,
"possible": true
}
},
{
"transformation": {
"select_id": 2,
"from": "IN (SELECT)",
"to": "semijoin",
"chosen": true
}
},
{
"expanded_query": "/* select#2 */ select t_inner_1.a from t2 t_inner_2 join t1 t_inner_1"
}
]
}
},
{
"join_preparation": {
"select_id": 3,
"steps": [
{
"transformation": {
"select_id": 3,
"from": "IN (SELECT)",
"to": "materialization",
"sjm_scan_allowed": true,
"possible": true
}
},
{
"transformation": {
"select_id": 3,
"from": "IN (SELECT)",
"to": "semijoin",
"chosen": true
}
},
{
"expanded_query": "/* select#3 */ select t_inner_3.a from t2 t_inner_3 join t1 t_inner_4"
}
]
}
},
{
"expanded_query": "/* select#1 */ select t_outer_1.a AS a,t_outer_2.a AS a from t1 t_outer_1 join t2 t_outer_2 where t_outer_1.a in (/* select#2 */ select t_inner_1.a from t2 t_inner_2 join t1 t_inner_1) and t_outer_2.a in (/* select#3 */ select t_inner_3.a from t2 t_inner_3 join t1 t_inner_4)"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"transformation": {
"select_id": 2,
"from": "IN (SELECT)",
"to": "semijoin",
"converted_to_semi_join": true
}
},
{
"transformation": {
"select_id": 3,
"from": "IN (SELECT)",
"to": "semijoin",
"converted_to_semi_join": true
}
},
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "1 and 1 and t_outer_1.a = t_inner_1.a and t_outer_2.a = t_inner_3.a",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "1 and 1 and multiple equal(t_outer_1.a, t_inner_1.a) and multiple equal(t_outer_2.a, t_inner_3.a)"
},
{
"transformation": "constant_propagation",
"resulting_condition": "1 and 1 and multiple equal(t_outer_1.a, t_inner_1.a) and multiple equal(t_outer_2.a, t_inner_3.a)"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "multiple equal(t_outer_1.a, t_inner_1.a) and multiple equal(t_outer_2.a, t_inner_3.a)"
}
]
}
},
{
"table_dependencies": [
{
"table": "t_outer_1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
},
{
"table": "t_outer_2",
"row_may_be_null": false,
"map_bit": 1,
"depends_on_map_bits": []
},
{
"table": "t_inner_2",
"row_may_be_null": false,
"map_bit": 2,
"depends_on_map_bits": []
},
{
"table": "t_inner_1",
"row_may_be_null": false,
"map_bit": 3,
"depends_on_map_bits": []
},
{
"table": "t_inner_3",
"row_may_be_null": false,
"map_bit": 4,
"depends_on_map_bits": []
},
{
"table": "t_inner_4",
"row_may_be_null": false,
"map_bit": 5,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": []
},
{
"rows_estimation": [
{
"table": "t_outer_1",
"table_scan": {
"rows": 3,
"cost": 2.005126953
}
},
{
"table": "t_outer_2",
"table_scan": {
"rows": 9,
"cost": 2.015380859
}
},
{
"table": "t_inner_2",
"table_scan": {
"rows": 9,
"cost": 2.015380859
}
},
{
"table": "t_inner_1",
"table_scan": {
"rows": 3,
"cost": 2.005126953
}
},
{
"table": "t_inner_3",
"table_scan": {
"rows": 9,
"cost": 2.015380859
}
},
{
"table": "t_inner_4",
"table_scan": {
"rows": 3,
"cost": 2.005126953
}
}
]
},
{
"semijoin_table_pullout": {
"pulled_out_tables": []
}
},
{
"semijoin_table_pullout": {
"pulled_out_tables": []
}
},
{
"execution_plan_for_potential_materialization": {
"steps": [
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t_inner_1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 2.605126953,
"rest_of_plan": [
{
"plan_prefix": ["t_inner_1"],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 27,
"cost_for_plan": 10.02050781,
"estimated_join_cardinality": 27
}
]
},
{
"plan_prefix": [],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": false
}
},
"rows_for_plan": 9,
"cost_for_plan": 3.815380859,
"pruned_by_heuristic": true
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t_inner_4",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 2.605126953,
"rest_of_plan": [
{
"plan_prefix": ["t_inner_4"],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 27,
"cost_for_plan": 10.02050781,
"estimated_join_cardinality": 27
}
]
},
{
"plan_prefix": [],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": false
}
},
"rows_for_plan": 9,
"cost_for_plan": 3.815380859,
"pruned_by_heuristic": true
}
]
}
]
}
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t_outer_1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 2.605126953,
"semijoin_strategy_choice": [],
"rest_of_plan": [
{
"plan_prefix": ["t_outer_1"],
"table": "t_inner_1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": true
}
},
"rows_for_plan": 9,
"cost_for_plan": 6.410253906,
"semijoin_strategy_choice": [],
"rest_of_plan": [
{
"plan_prefix": ["t_outer_1", "t_inner_1"],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 81,
"cost_for_plan": 24.62563477,
"semijoin_strategy_choice": [
{
"strategy": "FirstMatch",
"records": 3,
"read_time": 44.75893555
},
{
"strategy": "SJ-Materialization",
"records": 3,
"read_time": 8.125634766
},
{
"strategy": "DuplicateWeedout",
"records": 3,
"read_time": 37.22563477
},
{
"chosen_strategy": "SJ-Materialization"
}
],
"rest_of_plan": [
{
"plan_prefix": ["t_outer_1", "t_inner_1", "t_inner_2"],
"table": "t_outer_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 27,
"cost_for_plan": 15.54101562,
"semijoin_strategy_choice": [],
"rest_of_plan": [
{
"plan_prefix": [
"t_outer_1",
"t_inner_1",
"t_inner_2",
"t_outer_2"
],
"table": "t_inner_4",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": true
}
},
"rows_for_plan": 81,
"cost_for_plan": 33.74614258,
"semijoin_strategy_choice": [],
"rest_of_plan": [
{
"plan_prefix": [
"t_outer_1",
"t_inner_1",
"t_inner_2",
"t_outer_2",
"t_inner_4"
],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 729,
"cost_for_plan": 181.5615234,
"semijoin_strategy_choice": [
{
"strategy": "FirstMatch",
"records": 27,
"read_time": 394.925293
},
{
"strategy": "SJ-Materialization",
"records": 27,
"read_time": 22.26152344
},
{
"strategy": "DuplicateWeedout",
"records": 27,
"read_time": 294.9615234
},
{
"chosen_strategy": "SJ-Materialization"
}
],
"estimated_join_cardinality": 27
}
]
},
{
"plan_prefix": [
"t_outer_1",
"t_inner_1",
"t_inner_2",
"t_outer_2"
],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 243,
"cost_for_plan": 66.15639648,
"semijoin_strategy_choice": [],
"pruned_by_cost": true
}
]
},
{
"plan_prefix": ["t_outer_1", "t_inner_1", "t_inner_2"],
"table": "t_inner_4",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": true
}
},
"rows_for_plan": 9,
"cost_for_plan": 11.93076172,
"semijoin_strategy_choice": [],
"rest_of_plan": [
{
"plan_prefix": [
"t_outer_1",
"t_inner_1",
"t_inner_2",
"t_inner_4"
],
"table": "t_outer_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 81,
"cost_for_plan": 30.14614258,
"semijoin_strategy_choice": [],
"pruned_by_cost": true
},
{
"plan_prefix": [
"t_outer_1",
"t_inner_1",
"t_inner_2",
"t_inner_4"
],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 81,
"cost_for_plan": 30.14614258,
"semijoin_strategy_choice": [],
"pruned_by_cost": true
}
]
},
{
"plan_prefix": ["t_outer_1", "t_inner_1", "t_inner_2"],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 27,
"cost_for_plan": 15.54101562,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
}
]
},
{
"plan_prefix": ["t_outer_1", "t_inner_1"],
"table": "t_outer_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 81,
"cost_for_plan": 24.62563477,
"semijoin_strategy_choice": [],
"pruned_by_cost": true
},
{
"plan_prefix": ["t_outer_1", "t_inner_1"],
"table": "t_inner_4",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": true
}
},
"rows_for_plan": 27,
"cost_for_plan": 13.81538086,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": ["t_outer_1", "t_inner_1"],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 81,
"cost_for_plan": 24.62563477,
"semijoin_strategy_choice": [],
"pruned_by_cost": true
}
]
},
{
"plan_prefix": ["t_outer_1"],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 27,
"cost_for_plan": 10.02050781,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": ["t_outer_1"],
"table": "t_outer_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 27,
"cost_for_plan": 10.02050781,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": ["t_outer_1"],
"table": "t_inner_4",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": true
}
},
"rows_for_plan": 9,
"cost_for_plan": 6.410253906,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": ["t_outer_1"],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": true
}
},
"rows_for_plan": 27,
"cost_for_plan": 10.02050781,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
}
]
},
{
"plan_prefix": [],
"table": "t_inner_1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 2.605126953,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": false
}
},
"rows_for_plan": 9,
"cost_for_plan": 3.815380859,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_outer_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": false
}
},
"rows_for_plan": 9,
"cost_for_plan": 3.815380859,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_inner_4",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.005126953,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 3,
"cost": 2.005126953,
"uses_join_buffering": false
}
},
"rows_for_plan": 3,
"cost_for_plan": 2.605126953,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.015380859,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 9,
"cost": 2.015380859,
"uses_join_buffering": false
}
},
"rows_for_plan": 9,
"cost_for_plan": 3.815380859,
"semijoin_strategy_choice": [],
"pruned_by_heuristic": true
}
]
},
{
"fix_semijoin_strategies_for_picked_join_order": [
{
"semi_join_strategy": "SJ-Materialization",
"join_order": [
{
"table": "t_inner_4"
},
{
"table": "t_inner_3"
}
]
},
{
"semi_join_strategy": "SJ-Materialization",
"join_order": [
{
"table": "t_inner_1"
},
{
"table": "t_inner_2"
}
]
}
]
},
{
"best_join_order": [
"t_outer_1",
"<subquery2>",
"t_outer_2",
"<subquery3>"
]
},
{
"condition_on_constant_tables": "1",
"computing_condition": []
},
{
"attaching_conditions_to_tables": {
"original_condition": "1",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t_outer_1",
"attached": null
},
{
"table": "t_inner_1",
"attached": null
},
{
"table": "t_inner_2",
"attached": null
},
{
"table": "<subquery2>",
"attached": null
},
{
"table": "t_outer_2",
"attached": null
},
{
"table": "t_inner_4",
"attached": null
},
{
"table": "t_inner_3",
"attached": null
},
{
"table": "<subquery3>",
"attached": null
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
set @@optimizer_switch= @save_optimizer_switch;
drop table t1,t2;
#
# MDEV-18942: Json_writer::add_bool: Conditional jump or move depends on uninitialised value upon
# fulltext search under optimizer trace
#
CREATE TABLE t1 (f VARCHAR(255), FULLTEXT(f));
CREATE VIEW v1 AS SELECT * FROM t1;
INSERT INTO t1 VALUES ('fooba'),('abcde'),('xyzab');
SET optimizer_trace = 'enabled=on';
SELECT COUNT(*) FROM v1 WHERE MATCH (f) AGAINST ('fooba');
COUNT(*)
1
DROP VIEW v1;
DROP TABLE t1;
#
# MDEV-18741: Optimizer trace: multi-part key ranges are printed incorrectly.
#
create table t0(a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table one_k (a int);
insert into one_k select A.a + B.a*10 + C.a*100 from t0 A, t0 B, t0 C;
create table t1 ( a int, b int, key a_b(a,b));
insert into t1 select a,a from one_k;
set optimizer_trace='enabled=on';
explain select * from t1 force index (a_b) where a=2 and b=4;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref a_b a_b 10 const,const 1 Using index
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
{
"range_scan_alternatives":
[
{
"index": "a_b",
"ranges":
["(2,4) <= (a,b) <= (2,4)"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": true,
"rows": 1,
"cost": 0.345829876,
"chosen": true
}
],
"analyzing_roworder_intersect":
{
"cause": "too few roworder scans"
},
"analyzing_index_merge_union":
[]
}
]
explain select * from t1 where a >= 900 and b between 10 and 20;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range a_b a_b 10 NULL 107 Using where; Using index
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
{
"range_scan_alternatives":
[
{
"index": "a_b",
"ranges":
["(900,10) <= (a,b)"],
"rowid_ordered": false,
"using_mrr": false,
"index_only": true,
"rows": 107,
"cost": 21.63379668,
"chosen": true
}
],
"analyzing_roworder_intersect":
{
"cause": "too few roworder scans"
},
"analyzing_index_merge_union":
[]
}
]
drop table t0,t1;
create table t1 (start_date date, end_date date, filler char(100), key(start_date, end_date)) ;
insert into t1 select date_add(now(), interval a day), date_add(now(), interval (a+7) day), 'data' from one_k;
explain select * from t1 force index(start_date) where start_date >= '2019-02-10' and end_date <'2019-04-01';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range start_date start_date 8 NULL 1000 Using index condition
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
{
"range_scan_alternatives":
[
{
"index": "start_date",
"ranges":
["(2019-02-10,NULL) < (start_date,end_date)"],
"rowid_ordered": false,
"using_mrr": false,
"index_only": false,
"rows": 1000,
"cost": 1203.877243,
"chosen": true
}
],
"analyzing_roworder_intersect":
{
"cause": "too few roworder scans"
},
"analyzing_index_merge_union":
[]
}
]
drop table t1,one_k;
create table ten(a int);
insert into ten values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t1 (
a int not null,
b int not null,
c int not null,
d int not null,
key a_b_c(a,b,c)
);
insert into t1 select a,a, a,a from ten;
explain select * from t1 force index(a_b_c) where a between 1 and 4 and b < 50;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range a_b_c a_b_c 8 NULL 4 Using index condition
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
{
"range_scan_alternatives":
[
{
"index": "a_b_c",
"ranges":
["(1) <= (a,b) < (4,50)"],
"rowid_ordered": false,
"using_mrr": false,
"index_only": false,
"rows": 4,
"cost": 4.948710032,
"chosen": true
}
],
"analyzing_roworder_intersect":
{
"cause": "too few roworder scans"
},
"analyzing_index_merge_union":
[]
}
]
drop table ten,t1;
# Ported test from MYSQL for ranges involving Binary column
CREATE TABLE t1(i INT PRIMARY KEY, b BINARY(16), INDEX i_b(b));
INSERT INTO t1 VALUES (1, x'D95B94336A9946A39CF5B58CFE772D8C');
INSERT INTO t1 VALUES (2, NULL);
EXPLAIN SELECT * FROM t1 WHERE b IN (0xD95B94336A9946A39CF5B58CFE772D8C);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref i_b i_b 17 const 1 Using index condition
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
{
"range_scan_alternatives":
[
{
"index": "i_b",
"ranges":
["(\xD9[\x943j\x99F\xA3\x9C\xF5\xB5\x8C\xFEw-\x8C) <= (b) <= (\xD9[\x943j\x99F\xA3\x9C\xF5\xB5\x8C\xFEw-\x8C)"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": false,
"rows": 1,
"cost": 1.346171589,
"chosen": true
}
],
"analyzing_roworder_intersect":
{
"cause": "too few roworder scans"
},
"analyzing_index_merge_union":
[]
}
]
EXPLAIN SELECT * FROM t1 WHERE b IS NULL;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref i_b i_b 17 const 1 Using index condition
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
{
"range_scan_alternatives":
[
{
"index": "i_b",
"ranges":
["(NULL) <= (b) <= (NULL)"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": false,
"rows": 1,
"cost": 1.346171589,
"chosen": true
}
],
"analyzing_roworder_intersect":
{
"cause": "too few roworder scans"
},
"analyzing_index_merge_union":
[]
}
]
drop table t1;
#
# MDEV-18880: Optimizer trace prints date in hexadecimal
#
CREATE TABLE t1(i INT PRIMARY KEY, b VARCHAR(10) CHARSET BINARY , INDEX i_b(b));
INSERT INTO t1 VALUES (1, 'ab\n');
INSERT INTO t1 VALUES (2, NULL);
set optimizer_trace=1;
EXPLAIN SELECT * FROM t1 WHERE b='ab\n';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref i_b i_b 13 const 1 Using index condition
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
{
"range_scan_alternatives":
[
{
"index": "i_b",
"ranges":
["(ab\x0A) <= (b) <= (ab\x0A)"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": false,
"rows": 1,
"cost": 1.345927508,
"chosen": true
}
],
"analyzing_roworder_intersect":
{
"cause": "too few roworder scans"
},
"analyzing_index_merge_union":
[]
}
]
ALTER TABLE t1 modify column b BINARY(10) AFTER i;
EXPLAIN SELECT * FROM t1 WHERE b='ab\n';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref i_b i_b 11 const 1 Using index condition
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
{
"range_scan_alternatives":
[
{
"index": "i_b",
"ranges":
["(ab\x0A\x00\x00\x00\x00\x00\x00\x00) <= (b) <= (ab\x0A\x00\x00\x00\x00\x00\x00\x00)"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": false,
"rows": 1,
"cost": 1.345878692,
"chosen": true
}
],
"analyzing_roworder_intersect":
{
"cause": "too few roworder scans"
},
"analyzing_index_merge_union":
[]
}
]
ALTER TABLE t1 modify column b VARBINARY(10) AFTER i;
EXPLAIN SELECT * FROM t1 WHERE b='ab\n';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref i_b i_b 13 const 1 Using index condition
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
{
"range_scan_alternatives":
[
{
"index": "i_b",
"ranges":
["(ab\x0A) <= (b) <= (ab\x0A)"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": false,
"rows": 1,
"cost": 1.345927508,
"chosen": true
}
],
"analyzing_roworder_intersect":
{
"cause": "too few roworder scans"
},
"analyzing_index_merge_union":
[]
}
]
drop table t1;
CREATE TABLE t1(i INT PRIMARY KEY, b CHAR(10), INDEX i_b(b));
INSERT INTO t1 VALUES (1, 'ab\n');
INSERT INTO t1 VALUES (2, NULL);
EXPLAIN SELECT * FROM t1 WHERE b='ab\n';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref i_b i_b 11 const 1 Using index condition
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
{
"range_scan_alternatives":
[
{
"index": "i_b",
"ranges":
["(ab\n) <= (b) <= (ab\n)"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": false,
"rows": 1,
"cost": 1.345878692,
"chosen": true
}
],
"analyzing_roworder_intersect":
{
"cause": "too few roworder scans"
},
"analyzing_index_merge_union":
[]
}
]
drop table t1;
CREATE TABLE t1(i INT PRIMARY KEY, b blob , INDEX i_b(b));
Warnings:
Note 1071 Specified key was too long; max key length is 1000 bytes
INSERT INTO t1 VALUES (1, 'ab\n');
INSERT INTO t1 VALUES (2, NULL);
set optimizer_trace=1;
EXPLAIN SELECT * FROM t1 WHERE b= 'ab\n';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref i_b i_b 1003 const 1 Using where
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
{
"range_scan_alternatives":
[
{
"index": "i_b",
"ranges":
["(ab\x0A) <= (b) <= (ab\x0A)"],
"rowid_ordered": false,
"using_mrr": false,
"index_only": false,
"rows": 1,
"cost": 1.394255553,
"chosen": true
}
],
"analyzing_roworder_intersect":
{
"cause": "too few roworder scans"
},
"analyzing_index_merge_union":
[]
}
]
drop table t1;
CREATE TABLE t1(i INT PRIMARY KEY, b VARCHAR(10), INDEX i_b(b));
INSERT INTO t1 VALUES (1, 'ab\n');
INSERT INTO t1 VALUES (2, 'ab\n');
set optimizer_trace=1;
EXPLAIN SELECT * FROM t1 WHERE b='ab\n';
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref i_b i_b 13 const 2 Using index condition
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
{
"range_scan_alternatives":
[
{
"index": "i_b",
"ranges":
["(ab\n) <= (b) <= (ab\n)"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": false,
"rows": 2,
"cost": 2.546855016,
"chosen": true
}
],
"analyzing_roworder_intersect":
{
"cause": "too few roworder scans"
},
"analyzing_index_merge_union":
[]
}
]
drop table t1;
create table t0(a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table one_k (a int);
insert into one_k select A.a + B.a*10 + C.a*100 from t0 A, t0 B, t0 C;
create table t1 (start_date date, end_date date, filler char(100), key(start_date, end_date)) ;
insert into t1 select date_add(now(), interval a day), date_add(now(), interval (a+7) day), 'data' from one_k;
explain format=json select * from t1 force index(start_date) where start_date >= '2019-02-10' and end_date <'2019-04-01';
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t1",
"access_type": "range",
"possible_keys": ["start_date"],
"key": "start_date",
"key_length": "8",
"used_key_parts": ["start_date", "end_date"],
"rows": 1000,
"filtered": 100,
"index_condition": "t1.start_date >= '2019-02-10' and t1.end_date < '2019-04-01'"
}
}
}
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
{
"range_scan_alternatives":
[
{
"index": "start_date",
"ranges":
["(2019-02-10,NULL) < (start_date,end_date)"],
"rowid_ordered": false,
"using_mrr": false,
"index_only": false,
"rows": 1000,
"cost": 1203.877243,
"chosen": true
}
],
"analyzing_roworder_intersect":
{
"cause": "too few roworder scans"
},
"analyzing_index_merge_union":
[]
}
]
drop table t1, t0, one_k;
#
# MDEV-19776: Assertion `to_len >= 8' failed in convert_to_printable with optimizer trace enabled
#
CREATE TABLE t1 (f VARBINARY(16) NOT NULL, KEY(f));
INSERT INTO t1 VALUES ('a'),('b');
SET optimizer_trace = 'enabled=on';
DELETE FROM t1 WHERE f = 'x';
DROP TABLE t1;
#
# Print cost_for_plan and rows_for_plan for join prefix
#
create table t0(a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table one_k (a int, b int, key(b));
insert into one_k select A.a + B.a*10 + C.a*100, A.a + B.a*10 + C.a*100 from t0 A, t0 B, t0 C;
analyze table t0, one_k persistent for all;
Table Op Msg_type Msg_text
test.t0 analyze status Engine-independent statistics collected
test.t0 analyze status OK
test.one_k analyze status Engine-independent statistics collected
test.one_k analyze status Table is already up to date
set @tmp_jcl=@@join_cache_level;
set join_cache_level=0;
set optimizer_trace=1;
# Check cost/row numbers when multiple tables are joined
# (cost_for_plan is the same as best_access_path.cost for single-table SELECTs
# but for joins using condition selectivity it is not as trivial. So,
# now we are printing it)
explain select * from t0 A, one_k B where A.a<5 and B.a<800;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE A ALL NULL NULL NULL NULL 10 Using where
1 SIMPLE B ALL NULL NULL NULL NULL 1000 Using where
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.considered_execution_plans')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
[
{
"plan_prefix":
[],
"table": "A",
"best_access_path":
{
"considered_access_paths":
[
{
"access_type": "scan",
"resulting_rows": 5.9375,
"cost": 2.829589844,
"chosen": true
}
],
"chosen_access_method":
{
"type": "scan",
"records": 5.9375,
"cost": 2.829589844,
"uses_join_buffering": false
}
},
"rows_for_plan": 5.9375,
"cost_for_plan": 4.017089844,
"rest_of_plan":
[
{
"plan_prefix":
["A"],
"table": "B",
"best_access_path":
{
"considered_access_paths":
[
{
"access_type": "scan",
"resulting_rows": 804.6875,
"cost": 256.8548584,
"chosen": true
}
],
"chosen_access_method":
{
"type": "scan",
"records": 804.6875,
"cost": 256.8548584,
"uses_join_buffering": false
}
},
"rows_for_plan": 4777.832031,
"cost_for_plan": 1216.438354,
"estimated_join_cardinality": 4777.832031
}
]
},
{
"plan_prefix":
[],
"table": "B",
"best_access_path":
{
"considered_access_paths":
[
{
"access_type": "scan",
"resulting_rows": 804.6875,
"cost": 43.25976562,
"chosen": true
}
],
"chosen_access_method":
{
"type": "scan",
"records": 804.6875,
"cost": 43.25976562,
"uses_join_buffering": false
}
},
"rows_for_plan": 804.6875,
"cost_for_plan": 204.1972656,
"pruned_by_heuristic": true
}
]
]
set join_cache_level=@tmp_jcl;
# This shows post-join selectivity
explain select * from t0 A, one_k B where A.a=B.b and B.a<800;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE A ALL NULL NULL NULL NULL 10 Using where
1 SIMPLE B ref b b 5 test.A.a 1 Using where
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.considered_execution_plans')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
[
{
"plan_prefix":
[],
"table": "A",
"best_access_path":
{
"considered_access_paths":
[
{
"access_type": "scan",
"resulting_rows": 10,
"cost": 2.017089844,
"chosen": true
}
],
"chosen_access_method":
{
"type": "scan",
"records": 10,
"cost": 2.017089844,
"uses_join_buffering": false
}
},
"rows_for_plan": 10,
"cost_for_plan": 4.017089844,
"rest_of_plan":
[
{
"plan_prefix":
["A"],
"table": "B",
"best_access_path":
{
"considered_access_paths":
[
{
"access_type": "ref",
"index": "b",
"used_range_estimates": false,
"cause": "not available",
"rows": 1,
"cost": 20.00585794,
"chosen": true
},
{
"access_type": "scan",
"resulting_rows": 804.6875,
"cost": 43.25976562,
"chosen": false
}
],
"chosen_access_method":
{
"type": "ref",
"records": 1,
"cost": 20.00585794,
"uses_join_buffering": false
}
},
"rows_for_plan": 10,
"cost_for_plan": 26.02294779,
"selectivity": 0.8046875,
"estimated_join_cardinality": 8.046875
}
]
},
{
"plan_prefix":
[],
"table": "B",
"best_access_path":
{
"considered_access_paths":
[
{
"access_type": "scan",
"resulting_rows": 804.6875,
"cost": 43.25976562,
"chosen": true
}
],
"chosen_access_method":
{
"type": "scan",
"records": 804.6875,
"cost": 43.25976562,
"uses_join_buffering": false
}
},
"rows_for_plan": 804.6875,
"cost_for_plan": 204.1972656,
"pruned_by_cost": true
}
]
]
drop table t0, one_k;
#
# Assertion `to_len >= 8' failed in convert_to_printable
#
CREATE TABLE t1 ( a blob, KEY (a(255)));
insert into t1 values ('foo'), ('bar');
EXPLAIN SELECT * FROM t1 WHERE a= REPEAT('a', 0);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref a a 258 const 1 Using where
SELECT * FROM t1 WHERE a= REPEAT('a', 0);
a
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
{
"range_scan_alternatives":
[
{
"index": "a",
"ranges":
["() <= (a) <= ()"],
"rowid_ordered": false,
"using_mrr": false,
"index_only": false,
"rows": 1,
"cost": 1.357887479,
"chosen": true
}
],
"analyzing_roworder_intersect":
{
"cause": "too few roworder scans"
},
"analyzing_index_merge_union":
[]
}
]
DROP TABLE t1;
#
# Test for Semi-Join table pullout element
#
create table t1 (a int primary key, b int);
insert into t1 (a) values (1),(2),(3),(4),(5);
create table t2 (a int primary key, b int);
insert into t2 (a) values (1),(2),(3),(4),(5);
create table t3 (a int);
insert into t3 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
explain
select * from t3 where (a,a) in (select t1.a, t2.a from t1, t2 where t1.b=t2.b);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL PRIMARY NULL NULL NULL 5
1 PRIMARY t2 eq_ref PRIMARY PRIMARY 4 test.t1.a 1 Using where
1 PRIMARY t3 ALL NULL NULL NULL NULL 10 Using where; Using join buffer (flat, BNL join)
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.semijoin_table_pullout')) from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JSON_DETAILED(JSON_EXTRACT(trace, '$**.semijoin_table_pullout'))
[
{
"pulled_out_tables":
[
"t2",
"t1"
]
}
]
drop table t1,t2,t3;
#
# MDEV-22401: Optimizer trace: multi-component range is not printed correctly
#
create table t1 (kp1 int, kp2 int, key(kp1, kp2));
insert into t1 values (1,1),(1,5),(5,1),(5,5);
set optimizer_trace=1;
select * from t1 force index(kp1) where (kp1=2 and kp2 >=4);
kp1 kp2
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.range_scan_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
[
{
"index": "kp1",
"ranges":
["(2,4) <= (kp1,kp2) <= (2)"],
"rowid_ordered": false,
"using_mrr": false,
"index_only": true,
"rows": 1,
"cost": 0.345829876,
"chosen": true
}
]
]
drop table t1;
#
# MDEV-21626: Optimizer misses the details about the picked join order
#
CREATE TABLE t1(a INT, b INT, key(a));
INSERT INTO t1 SELECT seq, seq from seq_1_to_10;
CREATE TABLE t2(a INT, b INT, key(a));
INSERT INTO t2 SELECT seq, seq from seq_1_to_100;
SET OPTIMIZER_TRACE=1;
EXPLAIN SELECT * FROM t1, t2 WHERE t1.a=t2.a ORDER BY t2.b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL a NULL NULL NULL 10 Using where; Using temporary; Using filesort
1 SIMPLE t2 ref a a 5 test.t1.a 1
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.considered_execution_plans')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
[
{
"plan_prefix":
[],
"table": "t1",
"best_access_path":
{
"considered_access_paths":
[
{
"access_type": "scan",
"resulting_rows": 10,
"cost": 2.021972656,
"chosen": true
}
],
"chosen_access_method":
{
"type": "scan",
"records": 10,
"cost": 2.021972656,
"uses_join_buffering": false
}
},
"rows_for_plan": 10,
"cost_for_plan": 4.021972656,
"rest_of_plan":
[
{
"plan_prefix":
["t1"],
"table": "t2",
"best_access_path":
{
"considered_access_paths":
[
{
"access_type": "ref",
"index": "a",
"used_range_estimates": false,
"cause": "not available",
"rows": 1,
"cost": 20.00585794,
"chosen": true
},
{
"access_type": "scan",
"resulting_rows": 100,
"cost": 2.219726562,
"chosen": false
}
],
"chosen_access_method":
{
"type": "ref",
"records": 1,
"cost": 20.00585794,
"uses_join_buffering": false
}
},
"rows_for_plan": 10,
"cost_for_plan": 26.0278306,
"cost_for_sorting": 10,
"estimated_join_cardinality": 10
}
]
},
{
"plan_prefix":
[],
"table": "t2",
"best_access_path":
{
"considered_access_paths":
[
{
"access_type": "scan",
"resulting_rows": 100,
"cost": 2.219726562,
"chosen": true,
"use_tmp_table": true
}
],
"chosen_access_method":
{
"type": "scan",
"records": 100,
"cost": 2.219726562,
"uses_join_buffering": false
}
},
"rows_for_plan": 100,
"cost_for_plan": 22.21972656,
"rest_of_plan":
[
{
"plan_prefix":
["t2"],
"table": "t1",
"best_access_path":
{
"considered_access_paths":
[
{
"access_type": "ref",
"index": "a",
"used_range_estimates": false,
"cause": "not available",
"rows": 1,
"cost": 200.0585794,
"chosen": true
},
{
"access_type": "scan",
"resulting_rows": 10,
"cost": 2.021972656,
"chosen": true
}
],
"chosen_access_method":
{
"type": "scan",
"records": 10,
"cost": 2.021972656,
"uses_join_buffering": true
}
},
"rows_for_plan": 1000,
"cost_for_plan": 224.2416992,
"pruned_by_cost": true
}
]
}
]
]
DROP TABLE t1,t2;
#
# MDEV-22665: Print ranges in the optimizer trace created for non-indexed columns when
# optimizer_use_condition_selectivity >2
#
CREATE TABLE t1(a INT, b INT);
INSERT INTO t1 SELECT seq, seq from seq_1_to_100;
SET optimizer_trace=1;
ANALYZE TABLE t1 PERSISTENT FOR ALL;
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status OK
EXPLAIN EXTENDED SELECT * from t1 WHERE a between 1 and 5 and b <= 5;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 100 0.22 Using where
Warnings:
Note 1003 select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where `test`.`t1`.`a` between 1 and 5 and `test`.`t1`.`b` <= 5
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.selectivity_for_columns')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
[
{
"column_name": "a",
"ranges":
["1 <= a <= 5"],
"selectivity_from_histogram": 0.046875
},
{
"column_name": "b",
"ranges":
["NULL < b <= 5"],
"selectivity_from_histogram": 0.046875
}
]
]
EXPLAIN EXTENDED SELECT * from t1 WHERE a != 5;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 100 100.00 Using where
Warnings:
Note 1003 select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where `test`.`t1`.`a` <> 5
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.selectivity_for_columns')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
[
{
"column_name": "a",
"ranges":
[
"NULL < a < 5",
"5 < a"
],
"selectivity_from_histogram": 1
}
]
]
EXPLAIN EXTENDED SELECT * from t1 WHERE b >= 10 and b < 25;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 100 15.62 Using where
Warnings:
Note 1003 select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where `test`.`t1`.`b` >= 10 and `test`.`t1`.`b` < 25
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.selectivity_for_columns')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
[
{
"column_name": "b",
"ranges":
["10 <= b < 25"],
"selectivity_from_histogram": 0.15625
}
]
]
drop table t1;
#
# MDEV-22910:SIGSEGV in Opt_trace_context::is_started & SIGSEGV in Json_writer::add_table_name
# (on optimized builds)
#
CREATE TABLE t1( a INT, b INT, PRIMARY KEY( a ) );
SELECT sum(b), row_number() OVER (order by b) FROM t1 WHERE a = 101;
sum(b) row_number() OVER (order by b)
NULL 1
UPDATE t1 SET b=10 WHERE a=1;
SELECT JSON_DETAILED(JSON_EXTRACT(trace, '$**.range_scan_alternatives')) AS JS from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
JS
[
[
{
"index": "PRIMARY",
"ranges":
["(1) <= (a) <= (1)"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": false,
"rows": 0,
"cost": 0.145,
"chosen": true
}
]
]
DROP TABLE t1;
set optimizer_trace='enabled=off';
#
# MDEV-24975 Server consumes extra 4G memory upon querying INFORMATION_SCHEMA.OPTIIMIZER_TRACE
#
set max_session_mem_used=1024*1024*1024;
select count(*) from information_schema.optimizer_trace;
select * from information_schema.optimizer_trace;
set max_session_mem_used=default;
#
# MDEV-22380 Assertion `name.length == strlen(name.str)' failed in Item::print_item_w_name on SELECT w/ optimizer_trace enabled
#
SET optimizer_trace="enabled=on";
SELECT 'a\0' LIMIT 0;
a\x00
SELECT query, trace FROM INFORMATION_SCHEMA.OPTIMIZER_TRACE;
query trace
SELECT 'a\0' LIMIT 0 {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "select 'a\0' AS `a\x00` limit 0"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": []
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
}
SET optimizer_trace=DEFAULT;
#
# MDEV-27238: Assertion `got_name == named_item_expected()' failed in Json_writer::on_start_object
#
CREATE TABLE t1 (a INT KEY,b INT,KEY(b)) ENGINE=MEMORY;
SET optimizer_trace=1;
INSERT INTO t1 VALUES (0,0);
SELECT a FROM t1 WHERE (a,b) in (SELECT @c,@d);
a
DROP TABLE t1;
#
# MDEV-30964: MAX_SEL_ARG memory exhaustion is not visible in the optimizer trace
#
create table t1 (
c1 int,
c2 int,
c3 int,
c4 int,
c5 int,
c6 int,
c7 int,
c8 int,
key(c1,c2,c3,c4,c5,c6,c7,c8)
);
insert into t1 () values (),(),();
explain select *
from t1
where
(c1 in (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16) and c2=1) and
c3 in (1,2,3,4,5,6,7,8,9,10) and
c4 in (1,2,3,4,5,6,7,8,9,10) and
c5 in (1,2,3,4,5,6,7,8,9,10) and
c6 in (1,2,3,4);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 index c1 c1 40 NULL 3 Using where; Using index
select
json_detailed(json_extract(trace, '$**.setup_range_conditions'))
from
information_schema.optimizer_trace;
json_detailed(json_extract(trace, '$**.setup_range_conditions'))
[
[
{
"enforce_sel_arg_weight_limit":
{
"index": "c1",
"old_weight": 74806,
"new_weight": 1776
}
},
{
"sel_arg_alloc_limit_hit":
{
"alloced_sel_args": 16001
}
}
]
]
drop table t1;
#
# MDEV-31085: multi-update using view with optimizer trace enabled
#
SET SESSION optimizer_trace = 'enabled=on';
CREATE TABLE t (a int, b int);
CREATE VIEW v AS SELECT 1 AS c UNION SELECT 2 AS c;
INSERT INTO t VALUES (0,4),(5,6);
UPDATE t, v SET t.b = t.a, t.a = v.c WHERE v.c < t.a;
SELECT * FROM information_schema.optimizer_trace;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
UPDATE t, v SET t.b = t.a, t.a = v.c WHERE v.c < t.a {
"steps": [
{
"view": {
"table": "v",
"select_id": 2,
"algorithm": "materialized"
}
},
{
"join_preparation": {
"select_id": 2,
"steps": [
{
"expanded_query": "/* select#2 */ select 1 AS c"
}
]
}
},
{
"join_preparation": {
"select_id": 3,
"steps": [
{
"expanded_query": "/* select#3 */ select 2 AS c"
}
]
}
},
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "/* select#1 */ update t join v set t.b = t.a,t.a = v.c where v.c < t.a"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "v.c < t.a",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "v.c < t.a"
},
{
"transformation": "constant_propagation",
"resulting_condition": "v.c < t.a"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "v.c < t.a"
}
]
}
},
{
"join_optimization": {
"select_id": 2,
"steps": []
}
},
{
"join_optimization": {
"select_id": 3,
"steps": []
}
},
{
"table_dependencies": [
{
"table": "t",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
},
{
"table": "<derived2>",
"row_may_be_null": false,
"map_bit": 1,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": []
},
{
"rows_estimation": [
{
"table": "t",
"table_scan": {
"rows": 2,
"cost": 2.004394531
}
},
{
"table": "<derived2>",
"table_scan": {
"rows": 2,
"cost": 2
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 2,
"cost": 2.004394531,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 2,
"cost": 2.004394531,
"uses_join_buffering": false
}
},
"rows_for_plan": 2,
"cost_for_plan": 2.404394531,
"rest_of_plan": [
{
"plan_prefix": ["t"],
"table": "<derived2>",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 2,
"cost": 2,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 2,
"cost": 2,
"uses_join_buffering": true
}
},
"rows_for_plan": 4,
"cost_for_plan": 5.204394531,
"estimated_join_cardinality": 4
}
]
},
{
"plan_prefix": [],
"table": "<derived2>",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 2,
"cost": 2,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 2,
"cost": 2,
"uses_join_buffering": false
}
},
"rows_for_plan": 2,
"cost_for_plan": 2.4,
"rest_of_plan": [
{
"plan_prefix": ["<derived2>"],
"table": "t",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 2,
"cost": 2.004394531,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 2,
"cost": 2.004394531,
"uses_join_buffering": true
}
},
"rows_for_plan": 4,
"cost_for_plan": 5.204394531,
"pruned_by_cost": true
}
]
}
]
},
{
"best_join_order": ["t", "<derived2>"]
},
{
"attaching_conditions_to_tables": {
"original_condition": "v.c < t.a",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t",
"attached": null
},
{
"table": "<derived2>",
"attached": "v.c < t.a"
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": [
{
"join_execution": {
"select_id": 2,
"steps": []
}
},
{
"join_execution": {
"select_id": 3,
"steps": []
}
},
{
"join_preparation": {
"select_id": "fake",
"steps": [
{
"expanded_query": "select c AS c from dual"
}
]
}
},
{
"join_optimization": {
"select_id": "fake",
"steps": [
{
"table_dependencies": [
{
"table": "union",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"rows_estimation": [
{
"table": "union",
"table_scan": {
"rows": 2,
"cost": 10.1
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "union",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 2,
"cost": 10.1,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 2,
"cost": 10.1,
"uses_join_buffering": false
}
},
"rows_for_plan": 2,
"cost_for_plan": 10.5,
"estimated_join_cardinality": 2
}
]
},
{
"best_join_order": ["union"]
},
{
"attaching_conditions_to_tables": {
"original_condition": null,
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "union",
"attached": null
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": "fake",
"steps": []
}
}
]
}
}
]
} 0 0
SELECT * FROM t;
a b
0 4
1 5
SET optimizer_trace=DEFAULT;
DROP VIEW v;
DROP TABLE t;
#
# MDEV-26301: Split optimization improvements: Optimizer Trace coverage
#
create table t1(a int, b int);
insert into t1 select seq,seq from seq_1_to_5;
create table t2(a int, b int, key(a));
insert into t2
select A.seq,B.seq from seq_1_to_25 A, seq_1_to_2 B;
create table t3(a int, b int, key(a));
insert into t3
select A.seq,B.seq from seq_1_to_5 A, seq_1_to_3 B;
analyze table t1,t2,t3 persistent for all;
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status OK
test.t2 analyze status Engine-independent statistics collected
test.t2 analyze status Table is already up to date
test.t3 analyze status Engine-independent statistics collected
test.t3 analyze status Table is already up to date
create table t10 (
grp_id int,
col1 int,
key(grp_id)
);
insert into t10
select
A.seq,
B.seq
from
seq_1_to_100 A,
seq_1_to_100 B;
create table t11 (
col1 int,
col2 int
);
insert into t11
select A.seq, A.seq from seq_1_to_10 A;
analyze table t10,t11 persistent for all;
Table Op Msg_type Msg_text
test.t10 analyze status Engine-independent statistics collected
test.t10 analyze status Table is already up to date
test.t11 analyze status Engine-independent statistics collected
test.t11 analyze status OK
set optimizer_trace=1;
explain
select * from
(
(t1 left join t2 on t2.a=t1.b)
left join t3 on t3.a=t1.b
) left join (select grp_id, count(*)
from t10 left join t11 on t11.col1=t10.col1
group by grp_id) T on T.grp_id=t1.b;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 5
1 PRIMARY t2 ref a a 5 test.t1.b 2 Using where
1 PRIMARY t3 ref a a 5 test.t1.b 3 Using where
1 PRIMARY <derived2> ref key0 key0 5 test.t1.b 10 Using where
2 LATERAL DERIVED t10 ref grp_id grp_id 5 test.t1.b 100
2 LATERAL DERIVED t11 ALL NULL NULL NULL NULL 10 Using where; Using join buffer (flat, BNL join)
select json_detailed(json_extract(trace, '$**.check_split_materialized')) as JS
from information_schema.optimizer_trace;
JS
[
{
"split_candidates":
["t10.grp_id"]
}
]
select
json_detailed(
json_remove(
json_extract(trace, '$**.choose_best_splitting')
, '$[0].split_plan_search[0]'
)
) as JS
from information_schema.optimizer_trace;
JS
[
{
"considered_keys":
[
{
"table_name": "t10",
"index": "grp_id",
"rec_per_key": 100,
"param_tables": 1
}
],
"refills": 5,
"spl_pd_boundary": 2,
"split_plan_search":
[],
"lead_table": "t10",
"index": "grp_id",
"parts": 1,
"split_sel": 0.001,
"cost": 2535.968504,
"records": 100,
"refills": 5,
"chosen": true
}
]
drop table t1,t2,t3,t10,t11;
set optimizer_trace=DEFAULT;
#
# MDEV-29179 Condition pushdown from HAVING into WHERE is not shown in optimizer trace
#
CREATE TABLE t1 (a INT, b VARCHAR(1), KEY (a), KEY(b,a)) ENGINE=MEMORY;
INSERT INTO t1 VALUES (4,'n'),(1,'h'),(NULL,'w');
SET optimizer_trace= 'enabled=on';
SELECT b, a FROM t1 WHERE b <> 'p' OR a = 4 GROUP BY b, a HAVING a <= 7;
b a
h 1
n 4
SELECT json_detailed(json_extract(trace, '$**.steps[*].join_optimization.steps[*].condition_pushdown_from_having') ) exp1, JSON_VALID(trace) exp2 FROM information_schema.optimizer_trace;
exp1 exp2
[
{
"conds": "(t1.b <> 'p' or multiple equal(4, t1.a)) and t1.a <= 7",
"having": null
}
] 1
DROP TABLE t1;
#
# End of 10.4 tests
#
set optimizer_trace='enabled=on';
#
# Test many rows to see output of big cost numbers
#
select count(*) from seq_1_to_10000000;
count(*)
10000000
select * from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
select count(*) from seq_1_to_10000000 {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "select count(0) AS `count(*)` from seq_1_to_10000000"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"table_dependencies": [
{
"table": "seq_1_to_10000000",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"rows_estimation": [
{
"table": "seq_1_to_10000000",
"table_scan": {
"rows": 10000000,
"cost": 10000000
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "seq_1_to_10000000",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 10000000,
"cost": 10000000,
"chosen": true
}
],
"chosen_access_method": {
"type": "scan",
"records": 10000000,
"cost": 10000000,
"uses_join_buffering": false
}
},
"rows_for_plan": 10000000,
"cost_for_plan": 12000000,
"estimated_join_cardinality": 10000000
}
]
},
{
"best_join_order": ["seq_1_to_10000000"]
},
{
"attaching_conditions_to_tables": {
"original_condition": null,
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "seq_1_to_10000000",
"attached": null
}
]
}
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
#
# MDEV-22891: Optimizer trace: const tables are not clearly visible
#
create table t0(a int primary key);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t1 (pk int primary key, a int);
insert into t1 select a,a from t0;
create table t2 (pk int primary key, a int);
insert into t2 select a,a from t0;
create table t3 (pk int primary key, a int);
insert into t3 select a,a from t0;
explain
select * from t1 left join (t2 join t3 on t3.pk=1000) on t2.a=t1.a and t2.pk is null;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 const PRIMARY NULL NULL NULL 1 Impossible ON condition
1 SIMPLE t2 const PRIMARY NULL NULL NULL 1 Impossible ON condition
1 SIMPLE t1 ALL NULL NULL NULL NULL 10
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.mark_join_nest_as_const')) as jd
from information_schema.optimizer_trace;
jd
[
{
"members":
[
"t3",
"t2"
]
}
]
drop table t0, t1, t2, t3;
#
# MDEV-23767: IN-to-subquery conversion is not visible in optimizer trace
#
create table t0 (a int);
INSERT INTO t0 VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
set @tmp=@@in_predicate_conversion_threshold;
set in_predicate_conversion_threshold=3;
explain select * from t0 where a in (1,2,3,4,5,6);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t0 ALL NULL NULL NULL NULL 10 Using where
1 PRIMARY <derived3> ref key0 key0 4 test.t0.a 2 FirstMatch(t0)
3 DERIVED NULL NULL NULL NULL NULL NULL NULL No tables used
select json_detailed(json_extract(trace, '$**.in_to_subquery_conversion')) as jd
from information_schema.optimizer_trace;
jd
[
{
"item": "t0.a in (1,2,3,4,5,6)",
"conversion":
[
{
"join_preparation":
{
"select_id": 2,
"steps":
[
{
"derived":
{
"table": "tvc_0",
"select_id": 3,
"algorithm": "materialized"
}
},
{
"transformation":
{
"select_id": 2,
"from": "IN (SELECT)",
"to": "materialization",
"sjm_scan_allowed": true,
"possible": true
}
},
{
"transformation":
{
"select_id": 2,
"from": "IN (SELECT)",
"to": "semijoin",
"chosen": true
}
},
{
"expanded_query": "/* select#2 */ select tvc_0._col_1 from (values (1),(2),(3),(4),(5),(6)) tvc_0"
}
]
}
}
]
}
]
explain select * from t0 where a in (1,2,3,4,5,a+1);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t0 ALL NULL NULL NULL NULL 10 Using where
select json_detailed(json_extract(trace, '$**.in_to_subquery_conversion')) as jd
from information_schema.optimizer_trace;
jd
[
{
"item": "t0.a in (1,2,3,4,5,t0.a + 1)",
"done": false,
"reason": "non-constant element in the IN-list"
}
]
explain select * from t0 where a in ('1','2','3','4','5','6');
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t0 ALL NULL NULL NULL NULL 10 Using where
select json_detailed(json_extract(trace, '$**.in_to_subquery_conversion')) as jd
from information_schema.optimizer_trace;
jd
[
{
"item": "t0.a in ('1','2','3','4','5','6')",
"done": false,
"reason": "type mismatch"
}
]
set in_predicate_conversion_threshold=@tmp;
drop table t0;
#
# MDEV-29298: INSERT ... SELECT Does not produce an optimizer trace
#
create table t1 (a int, b int);
create table t2 (a int, b int);
insert into t1 values (1,1), (2,2), (3,3), (4,4), (5,5);
set optimizer_trace=1;
insert into t2 select * from t1 where a<= b and a>4;
select QUERY, LENGTH(trace)>1 from information_schema.optimizer_trace;
QUERY LENGTH(trace)>1
insert into t2 select * from t1 where a<= b and a>4 1
drop table t1, t2;
#
# MDEV-34305 Redundant truncation errors/warnings with optimizer_trace enabled
#
SET @@optimizer_trace='enabled=on';
CREATE TABLE t1 (
a CHAR(2) NOT NULL PRIMARY KEY,
b VARCHAR(20) NOT NULL,
KEY (b)
) CHARSET=utf8mb4;
CREATE TABLE t2 (
a CHAR(2) NOT NULL PRIMARY KEY,
b VARCHAR(20) NOT NULL,
KEY (b)
) CHARSET=utf8mb4;
INSERT INTO t1 VALUES
('AB','MySQLAB'),
('JA','Sun Microsystems'),
('MS','Microsoft'),
('IB','IBM- Inc.'),
('GO','Google Inc.');
INSERT IGNORE INTO t2 VALUES
('AB','Sweden'),
('JA','USA'),
('MS','United States'),
('IB','North America'),
('GO','South America');
UPDATE t1,t2 SET t1.b=UPPER(t1.b) WHERE t1.b LIKE 'Unknown%';
DROP TABLE t1, t2;
# End of 10.5 tests
set optimizer_trace='enabled=off';