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mariadb/mysql-test/main/opt_trace.result
Varun Gupta 9cb55143ac Minor cleanup in the optimizer trace code. 
More test coverage added for the optimizer trace.
2019-02-18 17:11:20 +05:30

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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
show variables like 'optimizer_trace';
Variable_name Value
optimizer_trace enabled=off
set optimizer_trace="enabled=on";
show variables like 'optimizer_trace';
Variable_name Value
optimizer_trace enabled=on
set 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",
"selectivity_from_histogram": 0.5
}
],
"cond_selectivity": 0.5
},
{
"table": "t1",
"table_scan": {
"rows": 2,
"cost": 2.0044
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 1,
"cost": 2.2044,
"chosen": true
}
]
}
}
]
},
{
"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",
"selectivity_from_histogram": 0.5
}
],
"cond_selectivity": 0.5
},
{
"table": "t1",
"table_scan": {
"rows": 2,
"cost": 2.0044
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 1,
"cost": 2.2044,
"chosen": true
}
]
}
}
]
},
{
"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",
"selectivity_from_histogram": 0.5
}
],
"cond_selectivity": 0.5
},
{
"table": "t1",
"table_scan": {
"rows": 2,
"cost": 2.0044
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 1,
"cost": 2.2044,
"chosen": true,
"use_tmp_table": true
}
]
}
}
]
},
{
"attaching_conditions_to_tables": {
"original_condition": "t1.a = 1",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": "t1.a = 1"
}
]
}
}
]
}
},
{
"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
}
]
}
}
]
},
{
"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
select * from information_schema.OPTIMIZER_TRACE;
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": 2.022
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 10,
"cost": 2.022,
"chosen": true
}
]
}
}
]
},
{
"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
select * from information_schema.OPTIMIZER_TRACE;
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": 2.022
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 10,
"cost": 2.022,
"chosen": true,
"use_tmp_table": true
}
]
}
}
]
},
{
"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": 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
}
]
}
}
]
},
{
"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": false
},
{
"table": "t2",
"field": "a",
"equals": "t1.b",
"null_rejecting": true
}
]
},
{
"rows_estimation": [
{
"table": "t1",
"table_scan": {
"rows": 100,
"cost": 2.3174
}
},
{
"table": "t2",
"table_scan": {
"rows": 100,
"cost": 2.3174
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 100,
"cost": 2.3174,
"chosen": true
}
]
},
"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,
"chosen": true
},
{
"access_type": "scan",
"resulting_rows": 100,
"cost": 2.3174,
"chosen": false
}
]
}
}
]
},
{
"plan_prefix": [],
"table": "t2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 100,
"cost": 2.3174,
"chosen": true
}
]
},
"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,
"chosen": true
},
{
"access_type": "scan",
"resulting_rows": 100,
"cost": 2.3174,
"chosen": false
}
]
},
"pruned_by_cost": true
}
]
}
]
},
{
"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
},
"potential_range_indexes": [
{
"index": "PRIMARY",
"usable": false,
"cause": "not applicable"
},
{
"index": "a",
"usable": true,
"key_parts": ["a"]
}
],
"best_covering_index_scan": {
"index": "a",
"cost": 4812.5,
"chosen": true
},
"group_index_range": {
"distinct_query": true,
"potential_group_range_indexes": [
{
"index": "a",
"covering": true,
"rows": 5,
"cost": 6.75
}
]
},
"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": 6.75,
"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": 6.75,
"key_parts_used_for_access": ["a"],
"ranges": []
},
"rows_for_plan": 5,
"cost_for_plan": 6.75,
"chosen": true
}
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "range",
"resulting_rows": 5,
"cost": 6.75,
"chosen": true
}
]
}
}
]
},
{
"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;
#
# 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 index NULL a 20 NULL 7 Using where; Using index
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": 5.5291
},
"potential_range_indexes": [
{
"index": "a",
"usable": true,
"key_parts": ["a", "b", "c", "d"]
}
],
"best_covering_index_scan": {
"index": "a",
"cost": 1.3869,
"chosen": true
},
"setup_range_conditions": [],
"group_index_range": {
"potential_group_range_indexes": [
{
"index": "a",
"covering": true,
"ranges": ["2 <= b <= 2 AND 3 <= c <= 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 <= b <= 2 AND 3 <= c <= 3"],
"chosen": false,
"cause": "cost"
},
"analyzing_range_alternatives": {
"range_scan_alternatives": [],
"analyzing_roworder_intersect": {
"cause": "too few roworder scans"
},
"analyzing_index_merge_union": []
}
}
},
{
"selectivity_for_indexes": [],
"selectivity_for_columns": [
{
"column_name": "b",
"selectivity_from_histogram": 0.2891
},
{
"column_name": "c",
"selectivity_from_histogram": 0.2891
}
],
"cond_selectivity": 0.0836
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 0.5849,
"cost": 3.3121,
"chosen": true,
"use_tmp_table": true
}
]
}
}
]
},
{
"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"
}
]
}
},
{
"reconsidering_access_paths_for_index_ordering": {
"clause": "GROUP BY",
"fanout": 1,
"read_time": 3.3131,
"table": "t1",
"rows_estimation": 7,
"possible_keys": [
{
"index": "a",
"can_resolve_order": true,
"updated_limit": 7,
"index_scan_time": 7,
"records": 7,
"chosen": true
}
]
}
}
]
}
},
{
"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 index NULL id 8 NULL 16 Using where; Using index
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": 7.3313
},
"potential_range_indexes": [
{
"index": "id",
"usable": true,
"key_parts": ["id", "a"]
}
],
"best_covering_index_scan": {
"index": "id",
"cost": 1.8468,
"chosen": true
},
"setup_range_conditions": [],
"group_index_range": {
"potential_group_range_indexes": [
{
"index": "id",
"covering": true,
"ranges": ["0x24a20f <= 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": ["0x24a20f <= a"],
"chosen": false,
"cause": "cost"
},
"analyzing_range_alternatives": {
"range_scan_alternatives": [],
"analyzing_roworder_intersect": {
"cause": "too few roworder scans"
},
"analyzing_index_merge_union": []
}
}
},
{
"selectivity_for_indexes": [],
"selectivity_for_columns": [],
"cond_selectivity": 1
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 16,
"cost": 2.0312,
"chosen": true,
"use_tmp_table": true
}
]
}
}
]
},
{
"attaching_conditions_to_tables": {
"original_condition": "t1.a >= 20010104e0",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": "t1.a >= 20010104e0"
}
]
}
},
{
"reconsidering_access_paths_for_index_ordering": {
"clause": "GROUP BY",
"fanout": 1,
"read_time": 2.0322,
"table": "t1",
"rows_estimation": 9,
"possible_keys": [
{
"index": "id",
"can_resolve_order": true,
"updated_limit": 16,
"index_scan_time": 16,
"records": 16,
"chosen": true
}
]
}
}
]
}
},
{
"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 index NULL id 8 NULL 16 Using where; Using index
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": 7.3313
},
"potential_range_indexes": [
{
"index": "id",
"usable": true,
"key_parts": ["id", "a"]
}
],
"best_covering_index_scan": {
"index": "id",
"cost": 1.8468,
"chosen": true
},
"setup_range_conditions": [],
"group_index_range": {
"potential_group_range_indexes": [
{
"index": "id",
"covering": true,
"ranges": ["0x24a20f <= a <= 0x24a20f"],
"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": ["0x24a20f <= a <= 0x24a20f"],
"chosen": false,
"cause": "cost"
},
"analyzing_range_alternatives": {
"range_scan_alternatives": [],
"analyzing_roworder_intersect": {
"cause": "too few roworder scans"
},
"analyzing_index_merge_union": []
}
}
},
{
"selectivity_for_indexes": [],
"selectivity_for_columns": [],
"cond_selectivity": 1
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 16,
"cost": 2.0312,
"chosen": true,
"use_tmp_table": true
}
]
}
}
]
},
{
"attaching_conditions_to_tables": {
"original_condition": "t1.a = 20010104e0",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": "t1.a = 20010104e0"
}
]
}
},
{
"reconsidering_access_paths_for_index_ordering": {
"clause": "GROUP BY",
"fanout": 1,
"read_time": 2.0322,
"table": "t1",
"rows_estimation": 9,
"possible_keys": [
{
"index": "id",
"can_resolve_order": true,
"updated_limit": 16,
"index_scan_time": 16,
"records": 16,
"chosen": true
}
]
}
}
]
}
},
{
"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": false
},
{
"table": "t1",
"field": "a",
"equals": "1",
"null_rejecting": false
},
{
"table": "t1",
"field": "b",
"equals": "2",
"null_rejecting": false
}
]
},
{
"rows_estimation": [
{
"table": "t1",
"range_analysis": {
"table_scan": {
"rows": 1000,
"cost": 232.66
},
"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": [],
"group_index_range": {
"chosen": false,
"cause": "no group by or distinct"
},
"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": 231.72,
"chosen": true
},
{
"index": "a_b",
"ranges": ["1 <= a <= 1 AND 2 <= b <= 2"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": false,
"rows": 21,
"cost": 27.445,
"chosen": true
}
],
"analyzing_roworder_intersect": {
"cause": "too few roworder scans"
},
"analyzing_index_merge_union": []
},
"chosen_range_access_summary": {
"range_access_plan": {
"type": "range_scan",
"index": "a_b",
"rows": 21,
"ranges": ["1 <= a <= 1 AND 2 <= b <= 2"]
},
"rows_for_plan": 21,
"cost_for_plan": 27.445,
"chosen": true
}
}
},
{
"selectivity_for_indexes": [
{
"index_name": "a_b",
"selectivity_from_index": 0.021
}
],
"selectivity_for_columns": [
{
"column_name": "a",
"selectivity_from_histogram": 0.1797
},
{
"column_name": "b",
"selectivity_from_histogram": 0.0156
}
],
"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,
"rows": 180,
"cost": 92,
"chosen": true
},
{
"access_type": "ref",
"index": "a_b",
"used_range_estimates": true,
"rows": 21,
"cost": 22,
"chosen": true
},
{
"type": "scan",
"chosen": false,
"cause": "cost"
}
]
}
}
]
},
{
"attaching_conditions_to_tables": {
"original_condition": "t1.a = 1 and t1.b = 2",
"attached_conditions_computation": [],
"attached_conditions_summary": [
{
"table": "t1",
"attached": null
}
]
}
},
{
"reconsidering_access_paths_for_index_ordering": {
"clause": "ORDER BY",
"fanout": 1,
"read_time": 22.001,
"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": 4.324,
"index_scan_time": 4.324,
"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": 1202
},
"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": [],
"group_index_range": {
"chosen": false,
"cause": "no group by or distinct"
},
"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": 231.72,
"chosen": true
}
],
"analyzing_roworder_intersect": {
"cause": "too few roworder scans"
},
"analyzing_index_merge_union": []
},
"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": 231.72,
"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": 2.0068
}
},
{
"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": 2.0068,
"chosen": true
}
]
}
}
]
},
{
"condition_on_constant_tables": "1"
},
{
"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": 2.0068
}
},
{
"table": "t2",
"table_scan": {
"rows": 2,
"cost": 2.0044
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 4,
"cost": 2.0068,
"chosen": true
}
]
},
"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": 8.0176,
"chosen": false
}
]
}
}
]
}
]
},
{
"condition_on_constant_tables": "1"
},
{
"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": 2.0068
}
},
{
"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": 2.0068,
"chosen": true
}
]
}
}
]
},
{
"condition_on_constant_tables": "1"
},
{
"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": 2.0066
}
},
{
"table": "t10",
"table_scan": {
"rows": 10,
"cost": 2.022
}
}
]
},
{
"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": 2.022,
"chosen": true
}
]
}
}
]
}
]
}
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.0066,
"chosen": true
}
]
},
"rest_of_plan": [
{
"plan_prefix": ["t1"],
"table": "t10",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 10,
"cost": 2.022,
"chosen": true
}
]
}
}
]
},
{
"plan_prefix": [],
"table": "t10",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 10,
"cost": 2.022,
"chosen": true
}
]
},
"pruned_by_heuristic": true
}
]
},
{
"fix_semijoin_strategies_for_picked_join_order": [
{
"semi_join_strategy": "sj_materialize",
"join_order": [
{
"table": "t10"
}
]
}
]
},
{
"condition_on_constant_tables": "1"
},
{
"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": false
},
{
"table": "t1",
"field": "pk",
"equals": "2",
"null_rejecting": false
},
{
"table": "t1",
"field": "a",
"equals": "5",
"null_rejecting": false
},
{
"table": "t1",
"field": "pk",
"equals": "2",
"null_rejecting": false
},
{
"table": "t1",
"field": "a",
"equals": "5",
"null_rejecting": false
},
{
"table": "t1",
"field": "b",
"equals": "1",
"null_rejecting": false
}
]
},
{
"rows_estimation": [
{
"table": "t1",
"range_analysis": {
"table_scan": {
"rows": 10,
"cost": 6.1317
},
"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": 1.5429,
"chosen": true
},
"setup_range_conditions": [],
"group_index_range": {
"chosen": false,
"cause": "no group by or distinct"
},
"analyzing_range_alternatives": {
"range_scan_alternatives": [
{
"index": "pk",
"ranges": ["2 <= pk <= 2"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": false,
"rows": 1,
"cost": 2.3773,
"chosen": false,
"cause": "cost"
},
{
"index": "pk_a",
"ranges": ["2 <= pk <= 2 AND 5 <= a <= 5"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": false,
"rows": 1,
"cost": 2.3783,
"chosen": false,
"cause": "cost"
},
{
"index": "pk_a_b",
"ranges": ["2 <= pk <= 2 AND 5 <= a <= 5 AND 1 <= b <= 1"],
"rowid_ordered": true,
"using_mrr": false,
"index_only": true,
"rows": 1,
"cost": 1.1793,
"chosen": true
}
],
"analyzing_roworder_intersect": {
"intersecting_indexes": [
{
"index": "pk",
"index_scan_cost": 1.0023,
"cumulateed_index_scan_cost": 1.0023,
"disk_sweep_cost": 0.9008,
"cumulative_total_cost": 1.9031,
"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": []
},
"chosen_range_access_summary": {
"range_access_plan": {
"type": "range_scan",
"index": "pk_a_b",
"rows": 1,
"ranges": ["2 <= pk <= 2 AND 5 <= a <= 5 AND 1 <= b <= 1"]
},
"rows_for_plan": 1,
"cost_for_plan": 1.1793,
"chosen": true
}
}
},
{
"selectivity_for_indexes": [
{
"index_name": "pk_a_b",
"selectivity_from_index": 0.1
}
],
"selectivity_for_columns": [
{
"column_name": "a",
"selectivity_from_histogram": 0.1
},
{
"column_name": "b",
"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": 2,
"chosen": true
},
{
"access_type": "ref",
"index": "pk_a",
"used_range_estimates": true,
"rows": 1,
"cost": 2,
"chosen": false,
"cause": "cost"
},
{
"access_type": "ref",
"index": "pk_a_b",
"used_range_estimates": true,
"rows": 1,
"cost": 1.0043,
"chosen": true
},
{
"type": "scan",
"chosen": false,
"cause": "cost"
}
]
}
}
]
},
{
"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": 2.0068
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 4,
"cost": 2.0068,
"chosen": true
}
]
}
}
]
},
{
"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": 2.0068
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 4,
"cost": 2.0068,
"chosen": true
}
]
}
}
]
},
{
"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)
1754
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": [
1654 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 1754 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": 6.122
},
"potential_range_indexes": [
{
"index": "a",
"usable": true,
"key_parts": ["a"]
}
],
"setup_range_conditions": [],
"group_index_range": {
"chosen": false,
"cause": "no join"
},
"analyzing_range_alternatives": {
"range_scan_alternatives": [
{
"index": "a",
"ranges": ["NULL < a < 3"],
"rowid_ordered": false,
"using_mrr": false,
"index_only": false,
"rows": 3,
"cost": 5.007,
"chosen": true
}
],
"analyzing_index_merge_union": []
},
"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": 5.007,
"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": "select NULL AS `NULL` from 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": 6.122
},
"potential_range_indexes": [
{
"index": "a",
"usable": true,
"key_parts": ["a"]
}
],
"best_covering_index_scan": {
"index": "a",
"cost": 1.5234,
"chosen": true
},
"setup_range_conditions": [],
"group_index_range": {
"chosen": false,
"cause": "not single_table"
},
"analyzing_range_alternatives": {
"range_scan_alternatives": [
{
"index": "a",
"ranges": ["NULL < a < 3"],
"rowid_ordered": false,
"using_mrr": false,
"index_only": true,
"rows": 3,
"cost": 1.407,
"chosen": true
}
],
"analyzing_roworder_intersect": {
"cause": "too few roworder scans"
},
"analyzing_index_merge_union": []
},
"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": 1.407,
"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": 6.122
},
"potential_range_indexes": [
{
"index": "a",
"usable": true,
"key_parts": ["a"]
}
],
"best_covering_index_scan": {
"index": "a",
"cost": 1.5234,
"chosen": true
},
"setup_range_conditions": [],
"group_index_range": {
"chosen": false,
"cause": "not single_table"
},
"analyzing_range_alternatives": {
"range_scan_alternatives": [
{
"index": "a",
"ranges": ["NULL < a < 3"],
"rowid_ordered": false,
"using_mrr": false,
"index_only": true,
"rows": 3,
"cost": 1.407,
"chosen": true
}
],
"analyzing_roworder_intersect": {
"cause": "too few roworder scans"
},
"analyzing_index_merge_union": []
},
"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": 1.407,
"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": 1.407,
"chosen": true
}
]
},
"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": 3.007,
"chosen": true
},
{
"type": "scan",
"chosen": false,
"cause": "cost"
}
]
}
}
]
},
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "range",
"resulting_rows": 3,
"cost": 1.407,
"chosen": true
}
]
},
"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",
"rows": 2,
"cost": 3.014,
"chosen": true
},
{
"type": "scan",
"chosen": false,
"cause": "cost"
}
]
},
"pruned_by_cost": true
}
]
}
]
},
{
"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": "merged"
}
},
{
"join_preparation": {
"select_id": 2,
"steps": [
{
"expanded_query": "/* select#2 */ select rand() AS `rand()` from t1"
}
]
}
},
{
"expanded_query": "/* select#1 */ select rand() AS `rand()` from (/* select#2 */ select rand() AS `rand()` from t1) q"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"derived": {
"table": "q",
"select_id": 2,
"algorithm": "materialized",
"cause": "Random function in the select"
}
},
{
"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": 2.0051
}
}
]
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.0051,
"chosen": true
}
]
}
}
]
},
{
"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
}
]
}
}
]
},
{
"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": 2.0051
}
},
{
"table": "t_inner_1",
"table_scan": {
"rows": 3,
"cost": 2.0051
}
},
{
"table": "t_inner_2",
"table_scan": {
"rows": 3,
"cost": 2.0051
}
}
]
},
{
"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": 2.0051,
"chosen": true
}
]
},
"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": 2.0051,
"chosen": true
}
]
}
}
]
},
{
"plan_prefix": [],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.0051,
"chosen": true
}
]
},
"pruned_by_heuristic": true
}
]
}
]
}
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.0051,
"chosen": true
}
]
},
"rest_of_plan": [
{
"plan_prefix": ["t1"],
"table": "t_inner_1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.0051,
"chosen": true
}
]
},
"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": 2.0051,
"chosen": true
}
]
}
}
]
},
{
"plan_prefix": ["t1"],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.0051,
"chosen": true
}
]
},
"pruned_by_heuristic": true
}
]
},
{
"plan_prefix": [],
"table": "t_inner_1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.0051,
"chosen": true
}
]
},
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.0051,
"chosen": true
}
]
},
"pruned_by_heuristic": true
}
]
},
{
"fix_semijoin_strategies_for_picked_join_order": [
{
"semi_join_strategy": "sj_materialize",
"join_order": [
{
"table": "t_inner_1"
},
{
"table": "t_inner_2"
}
]
}
]
},
{
"condition_on_constant_tables": "1"
},
{
"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; Using join buffer (flat, BNL join)
1 PRIMARY t_inner_2 ALL NULL NULL NULL NULL 9 FirstMatch(t_outer_1); 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_4 ALL NULL NULL NULL NULL 3 Using join buffer (incremental, BNL join)
1 PRIMARY t_inner_3 ALL NULL NULL NULL NULL 9 Using where; FirstMatch(t_outer_2); 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": 2.0051
}
},
{
"table": "t_outer_2",
"table_scan": {
"rows": 9,
"cost": 2.0154
}
},
{
"table": "t_inner_2",
"table_scan": {
"rows": 9,
"cost": 2.0154
}
},
{
"table": "t_inner_1",
"table_scan": {
"rows": 3,
"cost": 2.0051
}
},
{
"table": "t_inner_3",
"table_scan": {
"rows": 9,
"cost": 2.0154
}
},
{
"table": "t_inner_4",
"table_scan": {
"rows": 3,
"cost": 2.0051
}
}
]
},
{
"execution_plan_for_potential_materialization": {
"steps": []
}
},
{
"considered_execution_plans": [
{
"plan_prefix": [],
"table": "t_outer_1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.0051,
"chosen": true
}
]
},
"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": 2.0051,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0051,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
}
}
]
},
{
"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": 2.0154,
"chosen": true
}
]
},
"pruned_by_heuristic": 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": 2.0051,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"rest_of_plan": [
{
"plan_prefix": [
"t_outer_1",
"t_inner_1",
"t_inner_2",
"t_inner_4",
"t_outer_2"
],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"pruned_by_heuristic": 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": 2.0154,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"rest_of_plan": [
{
"plan_prefix": ["t_outer_1", "t_inner_1", "t_outer_2"],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"pruned_by_cost": true
},
{
"plan_prefix": ["t_outer_1", "t_inner_1", "t_outer_2"],
"table": "t_inner_4",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.0051,
"chosen": true
}
]
},
"rest_of_plan": [
{
"plan_prefix": [
"t_outer_1",
"t_inner_1",
"t_outer_2",
"t_inner_4"
],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"pruned_by_cost": true
},
{
"plan_prefix": [
"t_outer_1",
"t_inner_1",
"t_outer_2",
"t_inner_4"
],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"pruned_by_cost": true
}
]
},
{
"plan_prefix": ["t_outer_1", "t_inner_1", "t_outer_2"],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"pruned_by_heuristic": 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": 2.0051,
"chosen": true
}
]
},
"rest_of_plan": [
{
"plan_prefix": ["t_outer_1", "t_inner_1", "t_inner_4"],
"table": "t_outer_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"rest_of_plan": [
{
"plan_prefix": [
"t_outer_1",
"t_inner_1",
"t_inner_4",
"t_outer_2"
],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"pruned_by_cost": true
},
{
"plan_prefix": [
"t_outer_1",
"t_inner_1",
"t_inner_4",
"t_outer_2"
],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"pruned_by_cost": true
}
]
},
{
"plan_prefix": ["t_outer_1", "t_inner_1", "t_inner_4"],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"pruned_by_heuristic": true
},
{
"plan_prefix": ["t_outer_1", "t_inner_1", "t_inner_4"],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"rest_of_plan": [
{
"plan_prefix": ["t_outer_1", "t_inner_1", "t_inner_3"],
"table": "t_outer_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"rest_of_plan": [
{
"plan_prefix": [
"t_outer_1",
"t_inner_1",
"t_inner_3",
"t_outer_2"
],
"table": "t_inner_4",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.0051,
"chosen": true
}
]
},
"pruned_by_cost": true
},
{
"plan_prefix": [
"t_outer_1",
"t_inner_1",
"t_inner_3",
"t_outer_2"
],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"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": 2.0051,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0051,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"pruned_by_heuristic": true
}
]
},
{
"plan_prefix": [],
"table": "t_inner_1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.0051,
"chosen": true
}
]
},
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_outer_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_inner_4",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.0051,
"chosen": true
}
]
},
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"pruned_by_heuristic": true
}
]
},
{
"fix_semijoin_strategies_for_picked_join_order": [
{
"semi_join_strategy": "firstmatch",
"join_order": [
{
"table": "t_inner_4"
},
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 162.42,
"chosen": true
}
]
},
{
"table": "t_inner_3"
},
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 489.74,
"chosen": true
}
]
}
]
},
{
"semi_join_strategy": "firstmatch",
"join_order": [
{
"table": "t_inner_1"
},
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 18.046,
"chosen": true
}
]
},
{
"table": "t_inner_2"
},
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 54.415,
"chosen": true
}
]
}
]
}
]
},
{
"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_outer_2",
"attached": null
},
{
"table": "t_inner_4",
"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": 2.0051
}
},
{
"table": "t_outer_2",
"table_scan": {
"rows": 9,
"cost": 2.0154
}
},
{
"table": "t_inner_2",
"table_scan": {
"rows": 9,
"cost": 2.0154
}
},
{
"table": "t_inner_1",
"table_scan": {
"rows": 3,
"cost": 2.0051
}
},
{
"table": "t_inner_3",
"table_scan": {
"rows": 9,
"cost": 2.0154
}
},
{
"table": "t_inner_4",
"table_scan": {
"rows": 3,
"cost": 2.0051
}
}
]
},
{
"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": 2.0051,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
}
}
]
},
{
"plan_prefix": [],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"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": 2.0051,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
}
}
]
},
{
"plan_prefix": [],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"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": 2.0051,
"chosen": true
}
]
},
"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": 2.0051,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0051,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
}
}
]
},
{
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0051,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0051,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"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": 2.0051,
"chosen": true
}
]
},
"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": 2.0154,
"chosen": true
}
]
},
"pruned_by_heuristic": true
}
]
},
{
"plan_prefix": [],
"table": "t_inner_1",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.0051,
"chosen": true
}
]
},
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_inner_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_outer_2",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_inner_4",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 3,
"cost": 2.0051,
"chosen": true
}
]
},
"pruned_by_heuristic": true
},
{
"plan_prefix": [],
"table": "t_inner_3",
"best_access_path": {
"considered_access_paths": [
{
"access_type": "scan",
"resulting_rows": 9,
"cost": 2.0154,
"chosen": true
}
]
},
"pruned_by_heuristic": true
}
]
},
{
"fix_semijoin_strategies_for_picked_join_order": [
{
"semi_join_strategy": "sj_materialize",
"join_order": [
{
"table": "t_inner_4"
},
{
"table": "t_inner_3"
}
]
},
{
"semi_join_strategy": "sj_materialize",
"join_order": [
{
"table": "t_inner_1"
},
{
"table": "t_inner_2"
}
]
}
]
},
{
"condition_on_constant_tables": "1"
},
{
"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;
set optimizer_trace='enabled=off';
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