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mariadb/mysql-test/r/explain_json.result

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drop table if exists t0,t1,t2;
create table t0(a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
explain format=json select * from t0;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
}
explain format=json select * from t0 where 1>2;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"message": "Impossible WHERE"
}
}
}
explain format=json select * from t0 where a<3;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"attached_condition": "(t0.a < 3)"
}
}
}
# Try a basic join
create table t1 (a int, b int, filler char(32), key(a));
insert into t1
select
a.a + b.a* 10 + c.a * 100,
a.a + b.a* 10 + c.a * 100,
'filler'
from t0 a, t0 b, t0 c;
explain format=json select * from t0,t1 where t1.a=t0.a;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"attached_condition": "(t0.a is not null)"
},
"table": {
"table_name": "t1",
"access_type": "ref",
"possible_keys": ["a"],
"key": "a",
"key_length": "5",
"used_key_parts": ["a"],
"ref": ["test.t0.a"],
"rows": 1,
"filtered": 100
}
}
}
# Try range and index_merge
create table t2 (a1 int, a2 int, b1 int, b2 int, key(a1,a2), key(b1,b2));
insert into t2 select a,a,a,a from t1;
explain format=json select * from t2 where a1<5;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t2",
"access_type": "range",
"possible_keys": ["a1"],
"key": "a1",
"key_length": "5",
"used_key_parts": ["a1"],
"rows": 5,
"filtered": 100,
"index_condition": "(t2.a1 < 5)"
}
}
}
explain format=json select * from t2 where a1=1 or b1=2;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t2",
"access_type": "index_merge",
"possible_keys": ["a1", "b1"],
"key_length": "5,5",
"index_merge": {
"sort_union": {
"range": {
"key": "a1",
"used_key_parts": ["a1"]
},
"range": {
"key": "b1",
"used_key_parts": ["b1"]
}
}
},
"rows": 2,
"filtered": 100,
"attached_condition": "((t2.a1 = 1) or (t2.b1 = 2))"
}
}
}
explain format=json select * from t2 where a1=1 or (b1=2 and b2=3);
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t2",
"access_type": "index_merge",
"possible_keys": ["a1", "b1"],
"key_length": "5,10",
"index_merge": {
"sort_union": {
"range": {
"key": "a1",
"used_key_parts": ["a1"]
},
"range": {
"key": "b1",
"used_key_parts": ["b1", "b2"]
}
}
},
"rows": 2,
"filtered": 100,
"attached_condition": "((t2.a1 = 1) or ((t2.b1 = 2) and (t2.b2 = 3)))"
}
}
}
explain format=json select * from t2 where (a1=1 and a2=1) or
(b1=2 and b2=1);
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t2",
"access_type": "index_merge",
"possible_keys": ["a1", "b1"],
"key_length": "10,10",
"index_merge": {
"union": {
"range": {
"key": "a1",
"used_key_parts": ["a1", "a2"]
},
"range": {
"key": "b1",
"used_key_parts": ["b1", "b2"]
}
}
},
"rows": 2,
"filtered": 100,
"attached_condition": "(((t2.a1 = 1) and (t2.a2 = 1)) or ((t2.b1 = 2) and (t2.b2 = 1)))"
}
}
}
# Try ref access on two key components
explain format=json select * from t0,t2 where t2.b1=t0.a and t2.b2=4;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"attached_condition": "(t0.a is not null)"
},
"table": {
"table_name": "t2",
"access_type": "ref",
"possible_keys": ["b1"],
"key": "b1",
"key_length": "10",
"used_key_parts": ["b1", "b2"],
"ref": ["test.t0.a", "const"],
"rows": 1,
"filtered": 100
}
}
}
drop table t1,t2;
#
# Try a UNION
#
explain format=json select * from t0 A union select * from t0 B;
EXPLAIN
{
"query_block": {
"union_result": {
"table_name": "<union1,2>",
"access_type": "ALL",
"query_specifications": [
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "A",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
},
{
"query_block": {
"select_id": 2,
"table": {
"table_name": "B",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
}
]
}
}
}
explain format=json select * from t0 A union all select * from t0 B;
EXPLAIN
{
"query_block": {
"union_result": {
"table_name": "<union1,2>",
"access_type": "ALL",
"query_specifications": [
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "A",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
},
{
"query_block": {
"select_id": 2,
"table": {
"table_name": "B",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
}
]
}
}
}
#
# Subqueries
#
create table t1 (a int, b int);
insert into t1 select a,a from t0;
explain format=json select a, a > (select max(b) from t1 where t1.b=t0.a) from t0;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"filtered": 100
},
"subqueries": [
{
"query_block": {
"select_id": 2,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"attached_condition": "(t1.b = t0.a)"
}
}
}
]
}
}
explain format=json
select * from t0 where
a > (select max(b) from t1 where t1.b=t0.a) or a < 3 ;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"attached_condition": "((t0.a > (subquery#2)) or (t0.a < 3))"
},
"subqueries": [
{
"query_block": {
"select_id": 2,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"attached_condition": "(t1.b = t0.a)"
}
}
}
]
}
}
drop table t1;
#
# Join buffering
#
create table t1 (a int, b int);
insert into t1 select tbl1.a+10*tbl2.a, tbl1.a+10*tbl2.a from t0 tbl1, t0 tbl2;
explain format=json
select * from t1 tbl1, t1 tbl2 where tbl1.a=tbl2.a and tbl1.b < 3 and tbl2.b < 5;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "tbl1",
"access_type": "ALL",
"rows": 100,
"filtered": 100,
"attached_condition": "(tbl1.b < 3)"
},
"block-nl-join": {
"table": {
"table_name": "tbl2",
"access_type": "ALL",
"rows": 100,
"filtered": 100,
"attached_condition": "(tbl2.b < 5)"
},
"buffer_type": "flat",
"join_type": "BNL",
"attached_condition": "(tbl2.a = tbl1.a)"
}
}
}
drop table t1;
#
# Single-table UPDATE/DELETE, INSERT
#
explain format=json delete from t0;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"message": "Deleting all rows"
}
}
}
explain format=json delete from t0 where 1 > 2;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"message": "Impossible WHERE"
}
}
}
explain format=json delete from t0 where a < 3;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"delete": 1,
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"attached_condition": "(t0.a < 3)"
}
}
}
explain format=json update t0 set a=3 where a in (2,3,4);
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"update": 1,
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"attached_condition": "(t0.a in (2,3,4))"
}
}
}
explain format=json insert into t0 values (1);
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t0"
}
}
}
create table t1 like t0;
explain format=json insert into t1 values ((select max(a) from t0));
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t1"
},
"subqueries": [
{
"query_block": {
"select_id": 2,
"table": {
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
}
]
}
}
drop table t1;
#
# A derived table
#
create table t1 (a int, b int);
insert into t1 select a,a from t0;
explain format=json
select * from (select a, count(*) as cnt from t1 group by a) as tbl
where cnt>0;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "<derived2>",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"attached_condition": "(tbl.cnt > 0)",
"materialized": {
"query_block": {
"select_id": 2,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
}
}
}
}
explain format=json
select * from (select a, count(*) as cnt from t1 group by a) as tbl1, t1 as
tbl2 where cnt=tbl2.a;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "tbl2",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"attached_condition": "(tbl2.a is not null)"
},
"table": {
"table_name": "<derived2>",
"access_type": "ref",
"possible_keys": ["key0"],
"key": "key0",
"key_length": "8",
"used_key_parts": ["cnt"],
"ref": ["test.tbl2.a"],
"rows": 2,
"filtered": 100,
"attached_condition": "(tbl1.cnt = tbl2.a)",
"materialized": {
"query_block": {
"select_id": 2,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
}
}
}
}
#
# Non-merged semi-join (aka JTBM)
#
explain format=json
select * from t1 where a in (select max(a) from t1 group by b);
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"attached_condition": "(t1.a is not null)"
},
"table": {
"table_name": "<subquery2>",
"access_type": "eq_ref",
"possible_keys": ["distinct_key"],
"key": "distinct_key",
"key_length": "4",
"used_key_parts": ["max(a)"],
"ref": ["test.t1.a"],
"rows": 1,
"filtered": 100,
"materialized": {
"unique": 1,
"query_block": {
"select_id": 2,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
}
}
}
}
#
# Semi-join Materialization
#
create table t2 like t1;
insert into t2 select * from t1;
explain format=json
select * from t1,t2 where t1.a in ( select a from t0);
EXPLAIN
{
"query_block": {
"select_id": 1,
"const_condition": "1",
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 10,
"filtered": 100
},
"table": {
"table_name": "<subquery2>",
"access_type": "eq_ref",
"possible_keys": ["distinct_key"],
"key": "distinct_key",
"key_length": "4",
"used_key_parts": ["a"],
"ref": ["func"],
"rows": 1,
"filtered": 100,
"materialized": {
"unique": 1,
"query_block": {
"select_id": 2,
"table": {
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
}
},
"block-nl-join": {
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows": 10,
"filtered": 100
},
"buffer_type": "flat",
"join_type": "BNL"
}
}
}
#
# First-Match
#
explain
select * from t2 where t2.a in ( select a from t1 where t1.b=t2.b);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t2 ALL NULL NULL NULL NULL 10
1 PRIMARY t1 ALL NULL NULL NULL NULL 10 Using where; FirstMatch(t2); Using join buffer (flat, BNL join)
explain format=json
select * from t2 where t2.a in ( select a from t1 where t1.b=t2.b);
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows": 10,
"filtered": 100
},
"block-nl-join": {
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"first_match": "t2"
},
"buffer_type": "flat",
"join_type": "BNL",
"attached_condition": "((t1.b = t2.b) and (t1.a = t2.a))"
}
}
}
#
# Duplicate Weedout
#
set @tmp= @@optimizer_switch;
set optimizer_switch='firstmatch=off';
explain
select * from t2 where t2.a in ( select a from t1 where t1.b=t2.b);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t2 ALL NULL NULL NULL NULL 10
1 PRIMARY t1 ALL NULL NULL NULL NULL 10 Using where; Start temporary; End temporary; Using join buffer (flat, BNL join)
explain format=json
select * from t2 where t2.a in ( select a from t1 where t1.b=t2.b);
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows": 10,
"filtered": 100
},
"duplicates_removal": {
"block-nl-join": {
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 10,
"filtered": 100
},
"buffer_type": "flat",
"join_type": "BNL",
"attached_condition": "((t1.b = t2.b) and (t1.a = t2.a))"
}
}
}
}
set optimizer_switch=@tmp;
drop table t1,t2;
#
# MRR for range access (no BKA, just MRR)
#
create table t1 (a int, b int, key(a));
insert into t1 select tbl1.a+10*tbl2.a, 12345 from t0 tbl1, t0 tbl2;
set @tmp= @@optimizer_switch;
set optimizer_switch='mrr=on,mrr_sort_keys=on';
explain format=json select * from t1 where a < 3;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t1",
"access_type": "range",
"possible_keys": ["a"],
"key": "a",
"key_length": "5",
"used_key_parts": ["a"],
"rows": 1,
"filtered": 100,
"index_condition": "(t1.a < 3)",
"mrr_type": "Rowid-ordered scan"
}
}
}
# 'Range checked for each record'
set optimizer_switch=@tmp;
explain format=json
select * from t1 tbl1, t1 tbl2 where tbl2.a < tbl1.b;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "tbl1",
"access_type": "ALL",
"rows": 100,
"filtered": 100
},
"range-checked-for-each-record": {
"keys": ["a"],
"table": {
"table_name": "tbl2",
"access_type": "ALL",
"possible_keys": ["a"],
"rows": 100,
"filtered": 100
}
}
}
}
drop table t1;
drop table t0;
#
# MDEV-7265: "Full scan on NULL key", the join case
#
CREATE TABLE t1 (a INT, KEY(a));
INSERT INTO t1 VALUES (1),(2);
CREATE TABLE t2 (b INT);
INSERT INTO t2 VALUES (3),(4);
EXPLAIN FORMAT=JSON SELECT * FROM t1 AS outer_t1 WHERE a <> ALL ( SELECT a FROM t1, t2 WHERE b <> outer_t1.a );
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "outer_t1",
"access_type": "index",
"key": "a",
"key_length": "5",
"used_key_parts": ["a"],
"rows": 2,
"filtered": 100,
"attached_condition": "(not(<in_optimizer>(outer_t1.a,<exists>(subquery#2))))",
"using_index": true
},
"subqueries": [
{
"query_block": {
"select_id": 2,
"full-scan-on-null_key": {
"table": {
"table_name": "t1",
"access_type": "ref_or_null",
"possible_keys": ["a"],
"key": "a",
"key_length": "5",
"used_key_parts": ["a"],
"ref": ["func"],
"rows": 2,
"filtered": 100,
"attached_condition": "trigcond(((<cache>(outer_t1.a) = t1.a) or isnull(t1.a)))",
"using_index": true
}
},
"block-nl-join": {
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows": 2,
"filtered": 100
},
"buffer_type": "flat",
"join_type": "BNL",
"attached_condition": "((t2.b <> outer_t1.a) and trigcond(((<cache>(outer_t1.a) = t1.a) or isnull(t1.a))))"
}
}
}
]
}
}
DROP TABLE t1,t2;
#
# Join's constant expression
#
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 select tbl1.a+10*tbl2.a, 1234 from t0 tbl1, t0 tbl2;
explain format=json
select * from t0
where
20000 > all (select max(tbl1.a + tbl2.a)
from t1 tbl1, t1 tbl2 where tbl1.b=tbl2.b);
EXPLAIN
{
"query_block": {
"select_id": 1,
"const_condition": "<not>(<in_optimizer>(20000,(<max>(subquery#2) >= 20000)))",
"table": {
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"filtered": 100
},
"subqueries": [
{
"query_block": {
"select_id": 2,
"table": {
"table_name": "tbl1",
"access_type": "ALL",
"rows": 100,
"filtered": 100
},
"block-nl-join": {
"table": {
"table_name": "tbl2",
"access_type": "ALL",
"rows": 100,
"filtered": 100
},
"buffer_type": "flat",
"join_type": "BNL",
"attached_condition": "(tbl2.b = tbl1.b)"
}
}
}
]
}
}
drop table t1;
drop table t0;
#
# MDEV-7264: Assertion `0' failed in subselect_engine::get_identifier() on EXPLAIN JSON
#
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (1),(2);
CREATE TABLE t2 (b INT);
INSERT INTO t2 VALUES (3),(4);
EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE a <> ALL ( SELECT b FROM t2 );
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 2,
"filtered": 100,
"attached_condition": "(not(<in_optimizer>(t1.a,t1.a in (subquery#2))))"
},
"subqueries": [
{
"query_block": {
"select_id": 2,
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows": 2,
"filtered": 100
}
}
}
]
}
}
DROP TABLE t1, t2;
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