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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,
"nested_loop": [
{
"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,
"nested_loop": [
{
"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,
"nested_loop": [
{
"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,
"nested_loop": [
{
"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,
"nested_loop": [
{
"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,
"nested_loop": [
{
"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,
"nested_loop": [
{
"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,
"nested_loop": [
{
"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,
"nested_loop": [
{
"table": {
"table_name": "A",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
]
}
},
{
"query_block": {
"select_id": 2,
"operation": "UNION",
"nested_loop": [
{
"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": {
"query_specifications": [
{
"query_block": {
"select_id": 1,
"nested_loop": [
{
"table": {
"table_name": "A",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
]
}
},
{
"query_block": {
"select_id": 2,
"operation": "UNION",
"nested_loop": [
{
"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,
"nested_loop": [
{
"table": {
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
],
"subqueries": [
{
"expression_cache": {
"state": "uninitialized",
"query_block": {
"select_id": 2,
"nested_loop": [
{
"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,
"nested_loop": [
{
"table": {
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"attached_condition": "t0.a > (subquery#2) or t0.a < 3"
}
}
],
"subqueries": [
{
"expression_cache": {
"state": "uninitialized",
"query_block": {
"select_id": 2,
"nested_loop": [
{
"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,
"nested_loop": [
{
"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",
"buffer_size": "1KiB",
"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,
"nested_loop": [
{
"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,
"nested_loop": [
{
"table": {
"table_name": "<derived2>",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"attached_condition": "tbl.cnt > 0",
"materialized": {
"query_block": {
"select_id": 2,
"having_condition": "cnt > 0",
"filesort": {
"sort_key": "t1.a",
"temporary_table": {
"nested_loop": [
{
"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,
"nested_loop": [
{
"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,
"filesort": {
"sort_key": "t1.a",
"temporary_table": {
"nested_loop": [
{
"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,
"nested_loop": [
{
"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,
"materialization": {
"query_block": {
"select_id": 2,
"temporary_table": {
"nested_loop": [
{
"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",
"nested_loop": [
{
"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,
"nested_loop": [
{
"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",
"buffer_size": "1KiB",
"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,
"nested_loop": [
{
"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",
"buffer_size": "141",
"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,
"nested_loop": [
{
"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",
"buffer_size": "206",
"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,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "range",
"possible_keys": ["a"],
"key": "a",
"key_length": "5",
"used_key_parts": ["a"],
"rows": 2,
"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,
"nested_loop": [
{
"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,
"nested_loop": [
{
"table": {
"table_name": "outer_t1",
"access_type": "index",
"key": "a",
"key_length": "5",
"used_key_parts": ["a"],
"rows": 2,
"filtered": 100,
"attached_condition": "!<in_optimizer>(outer_t1.a,<exists>(subquery#2))",
"using_index": true
}
}
],
"subqueries": [
{
"query_block": {
"select_id": 2,
"having_condition": "trigcond(t1.a is null)",
"nested_loop": [
{
"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 t1.a is null)",
"using_index": true
}
}
},
{
"block-nl-join": {
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows": 2,
"filtered": 100
},
"buffer_type": "flat",
"buffer_size": "65",
"join_type": "BNL",
"attached_condition": "t2.b <> outer_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))",
"nested_loop": [
{
"table": {
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
],
"subqueries": [
{
"query_block": {
"select_id": 2,
"nested_loop": [
{
"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",
"buffer_size": "1KiB",
"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,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 2,
"filtered": 100,
"attached_condition": "!<in_optimizer>(t1.a,t1.a in (subquery#2))"
}
}
],
"subqueries": [
{
"materialization": {
"query_block": {
"select_id": 2,
"nested_loop": [
{
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows": 2,
"filtered": 100
}
}
]
}
}
}
]
}
}
DROP TABLE t1, t2;
#
# MDEV-7927: Server crashes in in Time_and_counter_tracker::incr_loops
#
CREATE TABLE t1 (i INT);
INSERT INTO t1 VALUES (1),(2);
EXPLAIN SELECT * FROM t1 WHERE 3 IN ( SELECT 4 UNION SELECT 5 );
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL No tables used
3 UNION NULL NULL NULL NULL NULL NULL NULL No tables used
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL
DROP TABLE t1;
#
# MDEV-7860: EXPLAIN FORMAT=JSON crashes for loose scan query
#
create table t2(a int);
insert into t2 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t1 (a int, b int, c int, d int, key(a,b,c));
insert into t1 select A.a, B.a, C.a, D.a from t2 A, t2 B, t2 C, t2 D;
explain select count(distinct b) from t1 group by a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range NULL a 10 NULL 101 Using index for group-by
explain format=json select count(distinct b) from t1 group by a;
EXPLAIN
{
"query_block": {
"select_id": 1,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "range",
"key": "a",
"key_length": "10",
"used_key_parts": ["a", "b"],
"rows": 101,
"filtered": 100,
"using_index_for_group_by": true
}
}
]
}
}
analyze format=json select count(distinct b) from t1 group by a;
ANALYZE
{
"query_optimization": {
"r_total_time_ms": "REPLACED"
},
"query_block": {
"select_id": 1,
"r_loops": 1,
"r_total_time_ms": "REPLACED",
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "range",
"key": "a",
"key_length": "10",
"used_key_parts": ["a", "b"],
"r_loops": 1,
"rows": 101,
"r_rows": 100,
"r_table_time_ms": "REPLACED",
"r_other_time_ms": "REPLACED",
"r_engine_stats": REPLACED,
"filtered": 100,
"r_filtered": 100,
"using_index_for_group_by": true
}
}
]
}
}
drop table t1,t2;
#
# Try both variants of LooseScan (data/queries borrowed from group_min_max.test)
#
create table t1 (
a1 char(64), a2 char(64), b char(16), c char(16) not null, d char(16), dummy char(248) default ' '
);
insert into t1 (a1, a2, b, c, d) values
('a','a','a','a111','xy1'),('a','a','a','b111','xy2'),('a','a','a','c111','xy3'),('a','a','a','d111','xy4'),
('a','a','b','e112','xy1'),('a','a','b','f112','xy2'),('a','a','b','g112','xy3'),('a','a','b','h112','xy4'),
('a','b','a','i121','xy1'),('a','b','a','j121','xy2'),('a','b','a','k121','xy3'),('a','b','a','l121','xy4'),
('a','b','b','m122','xy1'),('a','b','b','n122','xy2'),('a','b','b','o122','xy3'),('a','b','b','p122','xy4'),
('b','a','a','a211','xy1'),('b','a','a','b211','xy2'),('b','a','a','c211','xy3'),('b','a','a','d211','xy4'),
('b','a','b','e212','xy1'),('b','a','b','f212','xy2'),('b','a','b','g212','xy3'),('b','a','b','h212','xy4'),
('b','b','a','i221','xy1'),('b','b','a','j221','xy2'),('b','b','a','k221','xy3'),('b','b','a','l221','xy4'),
('b','b','b','m222','xy1'),('b','b','b','n222','xy2'),('b','b','b','o222','xy3'),('b','b','b','p222','xy4'),
('c','a','a','a311','xy1'),('c','a','a','b311','xy2'),('c','a','a','c311','xy3'),('c','a','a','d311','xy4'),
('c','a','b','e312','xy1'),('c','a','b','f312','xy2'),('c','a','b','g312','xy3'),('c','a','b','h312','xy4'),
('c','b','a','i321','xy1'),('c','b','a','j321','xy2'),('c','b','a','k321','xy3'),('c','b','a','l321','xy4'),
('c','b','b','m322','xy1'),('c','b','b','n322','xy2'),('c','b','b','o322','xy3'),('c','b','b','p322','xy4'),
('d','a','a','a411','xy1'),('d','a','a','b411','xy2'),('d','a','a','c411','xy3'),('d','a','a','d411','xy4'),
('d','a','b','e412','xy1'),('d','a','b','f412','xy2'),('d','a','b','g412','xy3'),('d','a','b','h412','xy4'),
('d','b','a','i421','xy1'),('d','b','a','j421','xy2'),('d','b','a','k421','xy3'),('d','b','a','l421','xy4'),
('d','b','b','m422','xy1'),('d','b','b','n422','xy2'),('d','b','b','o422','xy3'),('d','b','b','p422','xy4'),
('a','a','a','a111','xy1'),('a','a','a','b111','xy2'),('a','a','a','c111','xy3'),('a','a','a','d111','xy4'),
('a','a','b','e112','xy1'),('a','a','b','f112','xy2'),('a','a','b','g112','xy3'),('a','a','b','h112','xy4'),
('a','b','a','i121','xy1'),('a','b','a','j121','xy2'),('a','b','a','k121','xy3'),('a','b','a','l121','xy4'),
('a','b','b','m122','xy1'),('a','b','b','n122','xy2'),('a','b','b','o122','xy3'),('a','b','b','p122','xy4'),
('b','a','a','a211','xy1'),('b','a','a','b211','xy2'),('b','a','a','c211','xy3'),('b','a','a','d211','xy4'),
('b','a','b','e212','xy1'),('b','a','b','f212','xy2'),('b','a','b','g212','xy3'),('b','a','b','h212','xy4'),
('b','b','a','i221','xy1'),('b','b','a','j221','xy2'),('b','b','a','k221','xy3'),('b','b','a','l221','xy4'),
('b','b','b','m222','xy1'),('b','b','b','n222','xy2'),('b','b','b','o222','xy3'),('b','b','b','p222','xy4'),
('c','a','a','a311','xy1'),('c','a','a','b311','xy2'),('c','a','a','c311','xy3'),('c','a','a','d311','xy4'),
('c','a','b','e312','xy1'),('c','a','b','f312','xy2'),('c','a','b','g312','xy3'),('c','a','b','h312','xy4'),
('c','b','a','i321','xy1'),('c','b','a','j321','xy2'),('c','b','a','k321','xy3'),('c','b','a','l321','xy4'),
('c','b','b','m322','xy1'),('c','b','b','n322','xy2'),('c','b','b','o322','xy3'),('c','b','b','p322','xy4'),
('d','a','a','a411','xy1'),('d','a','a','b411','xy2'),('d','a','a','c411','xy3'),('d','a','a','d411','xy4'),
('d','a','b','e412','xy1'),('d','a','b','f412','xy2'),('d','a','b','g412','xy3'),('d','a','b','h412','xy4'),
('d','b','a','i421','xy1'),('d','b','a','j421','xy2'),('d','b','a','k421','xy3'),('d','b','a','l421','xy4'),
('d','b','b','m422','xy1'),('d','b','b','n422','xy2'),('d','b','b','o422','xy3'),('d','b','b','p422','xy4');
create index idx_t1_0 on t1 (a1);
create index idx_t1_1 on t1 (a1,a2,b,c);
create index idx_t1_2 on t1 (a1,a2,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
explain select count(distinct a1,a2,b) from t1 where (a2 >= 'b') and (b = 'a');
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range NULL idx_t1_1 147 NULL 17 Using where; Using index for group-by
explain select count(distinct a1,a2,b,c) from t1 where (a2 >= 'b') and (b = 'a') and (c = 'i121');
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range NULL idx_t1_1 163 NULL 65 Using where; Using index for group-by
explain format=json select count(distinct a1,a2,b) from t1 where (a2 >= 'b') and (b = 'a');
EXPLAIN
{
"query_block": {
"select_id": 1,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "range",
"key": "idx_t1_1",
"key_length": "147",
"used_key_parts": ["a1", "a2", "b"],
"rows": 17,
"filtered": 100,
"attached_condition": "t1.b = 'a' and t1.a2 >= 'b'",
"using_index_for_group_by": true
}
}
]
}
}
explain format=json select count(distinct a1,a2,b,c) from t1 where (a2 >= 'b') and (b = 'a') and (c = 'i121');
EXPLAIN
{
"query_block": {
"select_id": 1,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "range",
"key": "idx_t1_1",
"key_length": "163",
"used_key_parts": ["a1", "a2", "b", "c"],
"rows": 65,
"filtered": 100,
"attached_condition": "t1.b = 'a' and t1.c = 'i121' and t1.a2 >= 'b'",
"using_index_for_group_by": true
}
}
]
}
}
drop table t1;
#
# MDEV-8786 Wrong result for SELECT FORMAT=JSON * FROM t1 WHERE a=_latin1 0xDF
#
CREATE TABLE t1 (a VARCHAR(10) CHARACTER SET latin1);
INSERT INTO t1 VALUES ('a'),('b');
EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE a=_latin1 0xDF;
EXPLAIN
{
"query_block": {
"select_id": 1,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 2,
"filtered": 100,
"attached_condition": "t1.a = _latin1'\xDF'"
}
}
]
}
}
DROP TABLE t1;
#
# MDEV-8785 Wrong results for EXPLAIN EXTENDED...WHERE NULLIF(latin1_col, _utf8'a' COLLATE utf8_bin) IS NOT NULL
#
CREATE TABLE t1 (a VARCHAR(10) CHARACTER SET latin1);
INSERT INTO t1 VALUES ('a'),('A');
EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE NULLIF(a,_utf8'a' COLLATE utf8_bin);
EXPLAIN
{
"query_block": {
"select_id": 1,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 2,
"filtered": 100,
"attached_condition": "(case when convert(t1.a using utf8mb3) = <cache>(_utf8mb3'a' collate utf8mb3_bin) then NULL else t1.a end)"
}
}
]
}
}
DROP TABLE t1;
#
# MDEV-7970: EXPLAIN FORMAT=JSON does not print HAVING
#
create table t0(a int);
insert into t0 values (0),(1),(2),(3);
create table t1(a int);
insert into t1 select A.a + B.a* 10 + C.a * 100 from t0 A, t0 B, t0 C;
create table t2 (
a int,
b int,
key (a)
);
insert into t2 select A.a*1000 + B.a, A.a*1000 + B.a from t0 A, t1 B;
# normal HAVING
explain format=json select a, max(b) as TOP from t2 group by a having TOP > a;
EXPLAIN
{
"query_block": {
"select_id": 1,
"having_condition": "TOP > t2.a",
"filesort": {
"sort_key": "t2.a",
"temporary_table": {
"nested_loop": [
{
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows": 256,
"filtered": 100
}
}
]
}
}
}
}
# HAVING is always TRUE (not printed)
explain format=json select a, max(b) as TOP from t2 group by a having 1<>2;
EXPLAIN
{
"query_block": {
"select_id": 1,
"filesort": {
"sort_key": "t2.a",
"temporary_table": {
"nested_loop": [
{
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows": 256,
"filtered": 100
}
}
]
}
}
}
}
# HAVING is always FALSE (intercepted by message)
explain format=json select a, max(b) as TOP from t2 group by a having 1=2;
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"message": "Impossible HAVING"
}
}
}
# HAVING is absent
explain format=json select a, max(b) as TOP from t2 group by a;
EXPLAIN
{
"query_block": {
"select_id": 1,
"filesort": {
"sort_key": "t2.a",
"temporary_table": {
"nested_loop": [
{
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows": 256,
"filtered": 100
}
}
]
}
}
}
}
drop table t0, t1, t2;
#
# MDEV-8829: Assertion `0' failed in Explain_table_access::tag_to_json
#
# Check ET_CONST_ROW_NOT_FOUND
create table t1 (i int) engine=myisam;
explain
select * from t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 system NULL NULL NULL NULL 0 Const row not found
explain format=json
select * from t1;
EXPLAIN
{
"query_block": {
"select_id": 1,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "system",
"rows": 0,
"filtered": 0,
"const_row_not_found": true
}
}
]
}
}
analyze format=json
select * from t1;
ANALYZE
{
"query_optimization": {
"r_total_time_ms": "REPLACED"
},
"query_block": {
"select_id": 1,
"table": {
"message": "no matching row in const table"
}
}
}
drop table t1;
# Check ET_IMPOSSIBLE_ON_CONDITION
create table t1 (a int);
create table t2 (pk int primary key);
insert into t1 values (1),(2);
insert into t2 values (1),(2);
explain
select * from t1 left join t2 on t2.pk > 10 and t2.pk < 0;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 const PRIMARY NULL NULL NULL 1 Impossible ON condition
1 SIMPLE t1 ALL NULL NULL NULL NULL 2
explain format=json
select * from t1 left join t2 on t2.pk > 10 and t2.pk < 0;
EXPLAIN
{
"query_block": {
"select_id": 1,
"const_condition": "1",
"nested_loop": [
{
"table": {
"table_name": "t2",
"access_type": "const",
"possible_keys": ["PRIMARY"],
"rows": 1,
"filtered": 100,
"impossible_on_condition": true
}
},
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 2,
"filtered": 100
}
}
]
}
}
analyze format=json
select * from t1 left join t2 on t2.pk > 10 and t2.pk < 0;
ANALYZE
{
"query_optimization": {
"r_total_time_ms": "REPLACED"
},
"query_block": {
"select_id": 1,
"r_loops": 1,
"r_total_time_ms": "REPLACED",
"const_condition": "1",
"nested_loop": [
{
"table": {
"table_name": "t2",
"access_type": "const",
"possible_keys": ["PRIMARY"],
"r_loops": 0,
"rows": 1,
"r_rows": null,
"r_engine_stats": REPLACED,
"filtered": 100,
"r_filtered": null,
"impossible_on_condition": true
}
},
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"r_loops": 1,
"rows": 2,
"r_rows": 2,
"r_table_time_ms": "REPLACED",
"r_other_time_ms": "REPLACED",
"r_engine_stats": REPLACED,
"filtered": 100,
"r_filtered": 100
}
}
]
}
}
# Check ET_NOT_EXISTS:
explain
select * from t1 left join t2 on t2.pk=t1.a where t2.pk is null;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 2
1 SIMPLE t2 eq_ref PRIMARY PRIMARY 4 test.t1.a 1 Using where; Using index; Not exists
explain format=json
select * from t1 left join t2 on t2.pk=t1.a where t2.pk is null;
EXPLAIN
{
"query_block": {
"select_id": 1,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 2,
"filtered": 100
}
},
{
"table": {
"table_name": "t2",
"access_type": "eq_ref",
"possible_keys": ["PRIMARY"],
"key": "PRIMARY",
"key_length": "4",
"used_key_parts": ["pk"],
"ref": ["test.t1.a"],
"rows": 1,
"filtered": 100,
"attached_condition": "trigcond(t2.pk is null) and trigcond(trigcond(t1.a is not null))",
"using_index": true,
"not_exists": true
}
}
]
}
}
analyze format=json
select * from t1 left join t2 on t2.pk=t1.a where t2.pk is null;
ANALYZE
{
"query_optimization": {
"r_total_time_ms": "REPLACED"
},
"query_block": {
"select_id": 1,
"r_loops": 1,
"r_total_time_ms": "REPLACED",
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"r_loops": 1,
"rows": 2,
"r_rows": 2,
"r_table_time_ms": "REPLACED",
"r_other_time_ms": "REPLACED",
"r_engine_stats": REPLACED,
"filtered": 100,
"r_filtered": 100
}
},
{
"table": {
"table_name": "t2",
"access_type": "eq_ref",
"possible_keys": ["PRIMARY"],
"key": "PRIMARY",
"key_length": "4",
"used_key_parts": ["pk"],
"ref": ["test.t1.a"],
"r_loops": 2,
"rows": 1,
"r_rows": 1,
"r_table_time_ms": "REPLACED",
"r_other_time_ms": "REPLACED",
"r_engine_stats": REPLACED,
"filtered": 100,
"r_filtered": 100,
"attached_condition": "trigcond(t2.pk is null) and trigcond(trigcond(t1.a is not null))",
"using_index": true,
"not_exists": true
}
}
]
}
}
# Check ET_DISTINCT
explain
select distinct t1.a from t1 join t2 on t2.pk=t1.a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 2 Using where; Using temporary
1 SIMPLE t2 eq_ref PRIMARY PRIMARY 4 test.t1.a 1 Using index; Distinct
explain format=json
select distinct t1.a from t1 join t2 on t2.pk=t1.a;
EXPLAIN
{
"query_block": {
"select_id": 1,
"temporary_table": {
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 2,
"filtered": 100,
"attached_condition": "t1.a is not null"
}
},
{
"table": {
"table_name": "t2",
"access_type": "eq_ref",
"possible_keys": ["PRIMARY"],
"key": "PRIMARY",
"key_length": "4",
"used_key_parts": ["pk"],
"ref": ["test.t1.a"],
"rows": 1,
"filtered": 100,
"using_index": true,
"distinct": true
}
}
]
}
}
}
analyze format=json
select distinct t1.a from t1 join t2 on t2.pk=t1.a;
ANALYZE
{
"query_optimization": {
"r_total_time_ms": "REPLACED"
},
"query_block": {
"select_id": 1,
"r_loops": 1,
"r_total_time_ms": "REPLACED",
"temporary_table": {
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"r_loops": 1,
"rows": 2,
"r_rows": 2,
"r_table_time_ms": "REPLACED",
"r_other_time_ms": "REPLACED",
"r_engine_stats": REPLACED,
"filtered": 100,
"r_filtered": 100,
"attached_condition": "t1.a is not null"
}
},
{
"table": {
"table_name": "t2",
"access_type": "eq_ref",
"possible_keys": ["PRIMARY"],
"key": "PRIMARY",
"key_length": "4",
"used_key_parts": ["pk"],
"ref": ["test.t1.a"],
"r_loops": 2,
"rows": 1,
"r_rows": 1,
"r_table_time_ms": "REPLACED",
"r_other_time_ms": "REPLACED",
"r_engine_stats": REPLACED,
"filtered": 100,
"r_filtered": 100,
"using_index": true,
"distinct": true
}
}
]
}
}
}
drop table t1,t2;
# Check ET_USING_INDEX_CONDITION_BKA
create table t1(a int);
insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t2(a int);
insert into t2 select A.a + B.a* 10 + C.a * 100 from t1 A, t1 B, t1 C;
create table t3(a int, b int);
insert into t3 select a,a from t1;
create table t4(a int, b int, c int, filler char(100), key (a,b));
insert into t4 select a,a,a, 'filler-data' from t2;
set @tmp_optimizer_switch=@@optimizer_switch;
set @tmp_join_cache_level=@@join_cache_level;
set optimizer_switch='mrr=on';
set join_cache_level=6;
explain
select * from t3,t4 where t3.a=t4.a and (t4.b+1 <= t3.b+1);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 ALL NULL NULL NULL NULL 10 Using where
1 SIMPLE t4 ref a a 5 test.t3.a 1 Using index condition(BKA); Using join buffer (flat, BKA join); Rowid-ordered scan
explain format=json
select * from t3,t4 where t3.a=t4.a and (t4.b+1 <= t3.b+1);
EXPLAIN
{
"query_block": {
"select_id": 1,
"nested_loop": [
{
"table": {
"table_name": "t3",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"attached_condition": "t3.a is not null"
}
},
{
"block-nl-join": {
"table": {
"table_name": "t4",
"access_type": "ref",
"possible_keys": ["a"],
"key": "a",
"key_length": "5",
"used_key_parts": ["a"],
"ref": ["test.t3.a"],
"rows": 1,
"filtered": 100,
"index_condition_bka": "t4.b + 1 <= t3.b + 1"
},
"buffer_type": "flat",
"buffer_size": "400",
"join_type": "BKA",
"mrr_type": "Rowid-ordered scan"
}
}
]
}
}
analyze format=json
select * from t3,t4 where t3.a=t4.a and (t4.b+1 <= t3.b+1);
ANALYZE
{
"query_optimization": {
"r_total_time_ms": "REPLACED"
},
"query_block": {
"select_id": 1,
"r_loops": 1,
"r_total_time_ms": "REPLACED",
"nested_loop": [
{
"table": {
"table_name": "t3",
"access_type": "ALL",
"r_loops": 1,
"rows": 10,
"r_rows": 10,
"r_table_time_ms": "REPLACED",
"r_other_time_ms": "REPLACED",
"r_engine_stats": REPLACED,
"filtered": 100,
"r_filtered": 100,
"attached_condition": "t3.a is not null"
}
},
{
"block-nl-join": {
"table": {
"table_name": "t4",
"access_type": "ref",
"possible_keys": ["a"],
"key": "a",
"key_length": "5",
"used_key_parts": ["a"],
"ref": ["test.t3.a"],
"r_loops": 1,
"rows": 1,
"r_rows": 10,
"r_table_time_ms": "REPLACED",
"r_other_time_ms": "REPLACED",
"r_engine_stats": REPLACED,
"filtered": 100,
"r_filtered": 100,
"index_condition_bka": "t4.b + 1 <= t3.b + 1"
},
"buffer_type": "flat",
"buffer_size": "400",
"join_type": "BKA",
"mrr_type": "Rowid-ordered scan",
"r_loops": 10,
"r_filtered": 100,
"r_unpack_time_ms": "REPLACED",
"r_other_time_ms": "REPLACED",
"r_effective_rows": 1
}
}
]
}
}
set optimizer_switch=@tmp_optimizer_switch;
set join_cache_level=@tmp_join_cache_level;
drop table t1,t2,t3,t4;
#
# MDEV-9652: EXPLAIN FORMAT=JSON should show outer_ref_cond
#
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 a,a from t0;
explain format=json
select a, (select max(a) from t1 where t0.a<5 and t1.b<t0.a) from t0;
EXPLAIN
{
"query_block": {
"select_id": 1,
"nested_loop": [
{
"table": {
"table_name": "t0",
"access_type": "ALL",
"rows": 10,
"filtered": 100
}
}
],
"subqueries": [
{
"expression_cache": {
"state": "uninitialized",
"query_block": {
"select_id": 2,
"outer_ref_condition": "t0.a < 5",
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 10,
"filtered": 100,
"attached_condition": "t1.b < t0.a"
}
}
]
}
}
}
]
}
}
drop table t0,t1;
#
# MDEV-10844: EXPLAIN FORMAT=JSON doesn't show order direction for filesort
#
create table t1 (a int, b int);
insert into t1 values (1,2),(3,4),(2,3);
explain format=json select * from t1 order by a, b desc;
EXPLAIN
{
"query_block": {
"select_id": 1,
"nested_loop": [
{
"read_sorted_file": {
"filesort": {
"sort_key": "t1.a, t1.b desc",
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 3,
"filtered": 100
}
}
}
}
]
}
}
explain format=json select * from t1 order by a desc, b desc;
EXPLAIN
{
"query_block": {
"select_id": 1,
"nested_loop": [
{
"read_sorted_file": {
"filesort": {
"sort_key": "t1.a desc, t1.b desc",
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 3,
"filtered": 100
}
}
}
}
]
}
}
explain format=json select * from t1 order by a desc, b ;
EXPLAIN
{
"query_block": {
"select_id": 1,
"nested_loop": [
{
"read_sorted_file": {
"filesort": {
"sort_key": "t1.a desc, t1.b",
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows": 3,
"filtered": 100
}
}
}
}
]
}
}
drop table t1;
#
# MDEV-27204: [ERROR] Json_writer: a member name was expected, Assertion `got_name == named_item_expected()' failed
#
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (1),(2);
explain FORMAT=JSON
SELECT * FROM t1 t0
WHERE t0.a IN (SELECT t2.a FROM t1 t2 WHERE t0.a IN (SELECT t3.a FROM t1 t3));
EXPLAIN
{
"query_block": {
"select_id": 1,
"nested_loop": [
{
"table": {
"table_name": "t0",
"access_type": "ALL",
"rows": 2,
"filtered": 100
}
},
{
"duplicates_removal": [
{
"block-nl-join": {
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows": 2,
"filtered": 100
},
"buffer_type": "flat",
"buffer_size": "152",
"join_type": "BNL",
"attached_condition": "t2.a = t0.a"
}
},
{
"block-nl-join": {
"table": {
"table_name": "t3",
"access_type": "ALL",
"rows": 2,
"filtered": 100
},
"buffer_type": "incremental",
"buffer_size": "109",
"join_type": "BNL",
"attached_condition": "t3.a = t0.a"
}
}
]
}
]
}
}
DROP TABLE t1;
#
# MDEV-27206: [ERROR] Duplicated key: cause, Assertion `is_uniq_key' failed with optimizer trace
#
CREATE TABLE t1 (a INT) ENGINE=MyISAM;
CREATE TABLE t2 (pk TIME, b INT, primary key (pk), key (b)) ENGINE=MyISAM;
INSERT INTO t2 VALUES
('00:13:33',0),('00:13:34',1),('00:13:35',2),('00:13:36',3),
('00:13:37',4),('00:13:38',5),('00:13:39',6),('00:13:40',7),
('00:13:41',8),('00:13:42',9);
SET optimizer_trace = 'enabled=on';
SELECT * FROM t1 WHERE a IN ( SELECT b FROM t2 INNER JOIN t1 ON (a = pk) );
a
DROP TABLE t1, t2;