| Current Path : /home/usr.opt/mysql57/mysql-test/r/ |
FreeBSD hs32.drive.ne.jp 9.1-RELEASE FreeBSD 9.1-RELEASE #1: Wed Jan 14 12:18:08 JST 2015 root@hs32.drive.ne.jp:/sys/amd64/compile/hs32 amd64 |
| Current File : //home/usr.opt/mysql57/mysql-test/r/explain_json_all.result |
set optimizer_switch='semijoin=on,materialization=on,firstmatch=on,loosescan=on,index_condition_pushdown=on,mrr=on';
set @save_storage_engine= @@default_storage_engine;
set default_storage_engine=MyISAM;
set end_markers_in_json=on;
# new "FORMAT" keyword doesn't conflict with the FORMAT() function name:
SELECT FORMAT(1, 2), FORMAT(1, 2, 3);
FORMAT(1, 2) FORMAT(1, 2, 3)
1.00 1.00
Warnings:
Warning 1649 Unknown locale: '3'
# new "FORMAT" keyword is a valid identifier:
SET @FORMAT=10;
SELECT @FORMAT;
@FORMAT
10
CREATE TABLE t1 (format INT);
SELECT format FROM t1;
format
DROP TABLE t1;
# different ways of format name writing:
EXPLAIN FORMAT=traditional SELECT 1;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL NULL No tables used
Warnings:
Note 1003 /* select#1 */ select 1 AS `1`
EXPLAIN FORMAT='TrAdItIoNaL' SELECT 1;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL NULL No tables used
Warnings:
Note 1003 /* select#1 */ select 1 AS `1`
EXPLAIN FORMAT=JSON SELECT 1;
EXPLAIN
{
"query_block": {
"select_id": 1,
"message": "No tables used"
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select 1 AS `1`
EXPLAIN FORMAT=foo SELECT 1;
ERROR HY000: Unknown EXPLAIN format name: 'foo'
# various EXPLAIN output
CREATE TABLE t1 (i INT);
CREATE TABLE t2 (i INT);
CREATE TABLE t3 (i INT);
CREATE TABLE t4 (i INT);
# no end markers in JSON:
set end_markers_in_json=off;
EXPLAIN FORMAT=JSON SELECT * FROM t1;
EXPLAIN
{
"query_block": {
"select_id": 1,
"message": "no matching row in const table"
}
}
Warnings:
Note 1003 /* select#1 */ select NULL AS `i` from `test`.`t1`
set end_markers_in_json=on;
EXPLAIN INSERT INTO t1 VALUES (10);
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 INSERT t1 NULL ALL NULL NULL NULL NULL NULL NULL NULL
EXPLAIN FORMAT=JSON INSERT INTO t1 VALUES (10);
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"insert": true,
"table_name": "t1",
"access_type": "ALL"
} /* table */
} /* query_block */
}
EXPLAIN SELECT * FROM t1;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL NULL no matching row in const table
Warnings:
Note 1003 /* select#1 */ select NULL AS `i` from `test`.`t1`
PREPARE stmt FROM 'EXPLAIN FORMAT=JSON SELECT * FROM t1';
EXECUTE stmt;
EXPLAIN
{
"query_block": {
"select_id": 1,
"message": "no matching row in const table"
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select NULL AS `i` from `test`.`t1`
EXECUTE stmt;
EXPLAIN
{
"query_block": {
"select_id": 1,
"message": "no matching row in const table"
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select NULL AS `i` from `test`.`t1`
INSERT INTO t1 VALUES (1), (2), (3), (4), (5), (6), (7);
INSERT INTO t2 VALUES (1), (2);
# Check materialized derived table
set @optimizer_switch_saved= @@optimizer_switch;
set optimizer_switch='derived_merge=off';
EXPLAIN
SELECT * FROM (SELECT * FROM (SELECT * FROM (SELECT a1.i FROM (SELECT * FROM t1) a1, t2) a2) a3) a4;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 PRIMARY <derived2> NULL ALL NULL NULL NULL NULL 14 100.00 NULL
2 DERIVED <derived3> NULL ALL NULL NULL NULL NULL 14 100.00 NULL
3 DERIVED <derived4> NULL ALL NULL NULL NULL NULL 14 100.00 NULL
4 DERIVED t2 NULL ALL NULL NULL NULL NULL 2 100.00 NULL
4 DERIVED <derived5> NULL ALL NULL NULL NULL NULL 7 100.00 Using join buffer (Block Nested Loop)
5 DERIVED t1 NULL ALL NULL NULL NULL NULL 7 100.00 NULL
Warnings:
Note 1003 /* select#1 */ select `a4`.`i` AS `i` from (/* select#2 */ select `a3`.`i` AS `i` from (/* select#3 */ select `a2`.`i` AS `i` from (/* select#4 */ select `a1`.`i` AS `i` from (/* select#5 */ select `test`.`t1`.`i` AS `i` from `test`.`t1`) `a1` join `test`.`t2`) `a2`) `a3`) `a4`
EXPLAIN FORMAT=JSON
SELECT * FROM (SELECT * FROM (SELECT * FROM (SELECT a1.i FROM (SELECT * FROM t1) a1, t2) a2) a3) a4;
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "13.50"
} /* cost_info */,
"table": {
"table_name": "a4",
"access_type": "ALL",
"rows_examined_per_scan": 14,
"rows_produced_per_join": 14,
"filtered": "100.00",
"cost_info": {
"read_cost": "10.70",
"eval_cost": "2.80",
"prefix_cost": "13.50",
"data_read_per_join": "224"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */,
"materialized_from_subquery": {
"using_temporary_table": true,
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "13.50"
} /* cost_info */,
"table": {
"table_name": "a3",
"access_type": "ALL",
"rows_examined_per_scan": 14,
"rows_produced_per_join": 14,
"filtered": "100.00",
"cost_info": {
"read_cost": "10.70",
"eval_cost": "2.80",
"prefix_cost": "13.50",
"data_read_per_join": "224"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */,
"materialized_from_subquery": {
"using_temporary_table": true,
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 3,
"cost_info": {
"query_cost": "13.50"
} /* cost_info */,
"table": {
"table_name": "a2",
"access_type": "ALL",
"rows_examined_per_scan": 14,
"rows_produced_per_join": 14,
"filtered": "100.00",
"cost_info": {
"read_cost": "10.70",
"eval_cost": "2.80",
"prefix_cost": "13.50",
"data_read_per_join": "224"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */,
"materialized_from_subquery": {
"using_temporary_table": true,
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 4,
"cost_info": {
"query_cost": "15.55"
} /* cost_info */,
"nested_loop": [
{
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "16"
} /* cost_info */
} /* table */
},
{
"table": {
"table_name": "a1",
"access_type": "ALL",
"rows_examined_per_scan": 7,
"rows_produced_per_join": 14,
"filtered": "100.00",
"using_join_buffer": "Block Nested Loop",
"cost_info": {
"read_cost": "10.35",
"eval_cost": "2.80",
"prefix_cost": "15.55",
"data_read_per_join": "224"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */,
"materialized_from_subquery": {
"using_temporary_table": true,
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 5,
"cost_info": {
"query_cost": "3.41"
} /* cost_info */,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 7,
"rows_produced_per_join": 7,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "1.40",
"prefix_cost": "3.41",
"data_read_per_join": "56"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
} /* query_block */
} /* materialized_from_subquery */
} /* table */
}
] /* nested_loop */
} /* query_block */
} /* materialized_from_subquery */
} /* table */
} /* query_block */
} /* materialized_from_subquery */
} /* table */
} /* query_block */
} /* materialized_from_subquery */
} /* table */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select `a4`.`i` AS `i` from (/* select#2 */ select `a3`.`i` AS `i` from (/* select#3 */ select `a2`.`i` AS `i` from (/* select#4 */ select `a1`.`i` AS `i` from (/* select#5 */ select `test`.`t1`.`i` AS `i` from `test`.`t1`) `a1` join `test`.`t2`) `a2`) `a3`) `a4`
set optimizer_switch= @optimizer_switch_saved;
# subquery in WHERE
EXPLAIN SELECT * FROM t1 WHERE i IN (SELECT i FROM t2 WHERE t1.i = 10 ORDER BY RAND());
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 NULL ALL NULL NULL NULL NULL 7 14.29 Using where
1 SIMPLE t2 NULL ALL NULL NULL NULL NULL 2 50.00 Using where; FirstMatch(t1); Using join buffer (Block Nested Loop)
Warnings:
Note 1276 Field or reference 'test.t1.i' of SELECT #2 was resolved in SELECT #1
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` semi join (`test`.`t2`) where ((`test`.`t1`.`i` = 10) and (`test`.`t2`.`i` = 10))
EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE i IN (SELECT i FROM t2 WHERE t1.i = 10 ORDER BY RAND());
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "5.81"
} /* cost_info */,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 7,
"rows_produced_per_join": 0,
"filtered": "14.29",
"cost_info": {
"read_cost": "3.21",
"eval_cost": "0.20",
"prefix_cost": "3.41",
"data_read_per_join": "7"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */,
"attached_condition": "(`test`.`t1`.`i` = 10)"
} /* table */
},
{
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 0,
"filtered": "50.00",
"first_match": "t1",
"using_join_buffer": "Block Nested Loop",
"cost_info": {
"read_cost": "2.20",
"eval_cost": "0.20",
"prefix_cost": "5.82",
"data_read_per_join": "7"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */,
"attached_condition": "(`test`.`t2`.`i` = 10)"
} /* table */
}
] /* nested_loop */
} /* query_block */
}
Warnings:
Note 1276 Field or reference 'test.t1.i' of SELECT #2 was resolved in SELECT #1
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` semi join (`test`.`t2`) where ((`test`.`t1`.`i` = 10) and (`test`.`t2`.`i` = 10))
# two subqueries in WHERE
EXPLAIN SELECT * FROM t1
WHERE i IN (SELECT i FROM t2 WHERE t1.i = 10 ORDER BY RAND())
OR i IN (SELECT i FROM t4 ORDER BY RAND());
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 NULL ALL NULL NULL NULL NULL 7 100.00 Using where
3 UNCACHEABLE SUBQUERY NULL NULL NULL NULL NULL NULL NULL NULL NULL no matching row in const table
2 DEPENDENT SUBQUERY t2 NULL ALL NULL NULL NULL NULL 2 50.00 Using where
Warnings:
Note 1276 Field or reference 'test.t1.i' of SELECT #2 was resolved in SELECT #1
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` where (<in_optimizer>(`test`.`t1`.`i`,<exists>(/* select#2 */ select 1 from `test`.`t2` where ((`test`.`t1`.`i` = 10) and (<cache>(`test`.`t1`.`i`) = `test`.`t2`.`i`)))) or <in_optimizer>(`test`.`t1`.`i`,`test`.`t1`.`i` in ( <materialize> (/* select#3 */ select NULL from `test`.`t4` where 1 ), <primary_index_lookup>(`test`.`t1`.`i` in <temporary table> on <auto_key> where ((`test`.`t1`.`i` = `materialized-subquery`.`i`))))))
EXPLAIN FORMAT=JSON SELECT * FROM t1
WHERE i IN (SELECT i FROM t2 WHERE t1.i = 10 ORDER BY RAND())
OR i IN (SELECT i FROM t4 ORDER BY RAND());
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "3.41"
} /* cost_info */,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 7,
"rows_produced_per_join": 7,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "1.40",
"prefix_cost": "3.41",
"data_read_per_join": "56"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */,
"attached_condition": "(<in_optimizer>(`test`.`t1`.`i`,<exists>(/* select#2 */ select 1 from `test`.`t2` where ((`test`.`t1`.`i` = 10) and (<cache>(`test`.`t1`.`i`) = `test`.`t2`.`i`)))) or <in_optimizer>(`test`.`t1`.`i`,`test`.`t1`.`i` in ( <materialize> (/* select#3 */ select NULL from `test`.`t4` where 1 ), <primary_index_lookup>(`test`.`t1`.`i` in <temporary table> on <auto_key> where ((`test`.`t1`.`i` = `materialized-subquery`.`i`))))))",
"attached_subqueries": [
{
"table": {
"table_name": "<materialized_subquery>",
"access_type": "eq_ref",
"key": "<auto_key>",
"key_length": "5",
"rows_examined_per_scan": 1,
"materialized_from_subquery": {
"using_temporary_table": true,
"dependent": true,
"cacheable": false,
"query_block": {
"select_id": 3,
"message": "no matching row in const table"
} /* query_block */
} /* materialized_from_subquery */
} /* table */
},
{
"dependent": true,
"cacheable": false,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "2.40"
} /* cost_info */,
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 1,
"filtered": "50.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.20",
"prefix_cost": "2.40",
"data_read_per_join": "8"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */,
"attached_condition": "((`test`.`t1`.`i` = 10) and (<cache>(`test`.`t1`.`i`) = `test`.`t2`.`i`))"
} /* table */
} /* query_block */
}
] /* attached_subqueries */
} /* table */
} /* query_block */
}
Warnings:
Note 1276 Field or reference 'test.t1.i' of SELECT #2 was resolved in SELECT #1
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` where (<in_optimizer>(`test`.`t1`.`i`,<exists>(/* select#2 */ select 1 from `test`.`t2` where ((`test`.`t1`.`i` = 10) and (<cache>(`test`.`t1`.`i`) = `test`.`t2`.`i`)))) or <in_optimizer>(`test`.`t1`.`i`,`test`.`t1`.`i` in ( <materialize> (/* select#3 */ select NULL from `test`.`t4` where 1 ), <primary_index_lookup>(`test`.`t1`.`i` in <temporary table> on <auto_key> where ((`test`.`t1`.`i` = `materialized-subquery`.`i`))))))
# simple UNION
EXPLAIN SELECT * FROM t1 UNION SELECT * FROM t2 UNION SELECT * FROM t3;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 NULL ALL NULL NULL NULL NULL 7 100.00 NULL
2 UNION t2 NULL ALL NULL NULL NULL NULL 2 100.00 NULL
3 UNION NULL NULL NULL NULL NULL NULL NULL NULL NULL no matching row in const table
NULL UNION RESULT <union1,2,3> NULL ALL NULL NULL NULL NULL NULL NULL Using temporary
Warnings:
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` union /* select#2 */ select `test`.`t2`.`i` AS `i` from `test`.`t2` union /* select#3 */ select NULL AS `i` from `test`.`t3`
EXPLAIN FORMAT=JSON SELECT * FROM t1 UNION SELECT * FROM t2 UNION SELECT * FROM t3;
EXPLAIN
{
"query_block": {
"union_result": {
"using_temporary_table": true,
"table_name": "<union1,2,3>",
"access_type": "ALL",
"query_specifications": [
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "3.41"
} /* cost_info */,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 7,
"rows_produced_per_join": 7,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "1.40",
"prefix_cost": "3.41",
"data_read_per_join": "56"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
} /* query_block */
},
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "2.40"
} /* cost_info */,
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "16"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
} /* query_block */
},
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 3,
"message": "no matching row in const table"
} /* query_block */
}
] /* query_specifications */
} /* union_result */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` union /* select#2 */ select `test`.`t2`.`i` AS `i` from `test`.`t2` union /* select#3 */ select NULL AS `i` from `test`.`t3`
# more complex UNION
EXPLAIN (SELECT t1.i FROM t1 JOIN t2) UNION ALL (SELECT * FROM t3 WHERE i IN (SELECT i FROM t4 ORDER BY RAND()));
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t2 NULL ALL NULL NULL NULL NULL 2 100.00 NULL
1 PRIMARY t1 NULL ALL NULL NULL NULL NULL 7 100.00 Using join buffer (Block Nested Loop)
2 UNION NULL NULL NULL NULL NULL NULL NULL NULL NULL no matching row in const table
Warnings:
Note 1003 (/* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` join `test`.`t2`) union all (/* select#2 */ select NULL AS `i` from `test`.`t3` semi join (`test`.`t4`) where multiple equal(NULL, `test`.`t4`.`i`))
EXPLAIN FORMAT=JSON (SELECT t1.i FROM t1 JOIN t2) UNION ALL (SELECT * FROM t3 WHERE i IN (SELECT i FROM t4 ORDER BY RAND()));
EXPLAIN
{
"query_block": {
"union_result": {
"using_temporary_table": false,
"query_specifications": [
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "7.21"
} /* cost_info */,
"nested_loop": [
{
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "16"
} /* cost_info */
} /* table */
},
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 7,
"rows_produced_per_join": 14,
"filtered": "100.00",
"using_join_buffer": "Block Nested Loop",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "2.80",
"prefix_cost": "7.22",
"data_read_per_join": "112"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
}
] /* nested_loop */
} /* query_block */
},
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 2,
"message": "no matching row in const table"
} /* query_block */
}
] /* query_specifications */
} /* union_result */
} /* query_block */
}
Warnings:
Note 1003 (/* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` join `test`.`t2`) union all (/* select#2 */ select NULL AS `i` from `test`.`t3` semi join (`test`.`t4`) where multiple equal(NULL, `test`.`t4`.`i`))
# UNION with subquery in outer ORDER BY
EXPLAIN (SELECT * FROM t1) UNION (SELECT * FROM t2) ORDER BY (SELECT i LIMIT 1);
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 NULL ALL NULL NULL NULL NULL 7 100.00 NULL
2 UNION t2 NULL ALL NULL NULL NULL NULL 2 100.00 NULL
NULL UNION RESULT <union1,2> NULL ALL NULL NULL NULL NULL NULL NULL Using temporary; Using filesort
3 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL NULL NULL No tables used
Warnings:
Note 1276 Field or reference 'i' of SELECT #3 was resolved in SELECT #1
Note 1003 (/* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1`) union (/* select#2 */ select `test`.`t2`.`i` AS `i` from `test`.`t2`) order by (/* select#3 */ select `i` limit 1)
EXPLAIN FORMAT=JSON (SELECT * FROM t1) UNION (SELECT * FROM t2) ORDER BY (SELECT i LIMIT 1);
EXPLAIN
{
"query_block": {
"ordering_operation": {
"using_filesort": true,
"union_result": {
"using_temporary_table": true,
"table_name": "<union1,2>",
"access_type": "ALL",
"query_specifications": [
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "3.41"
} /* cost_info */,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 7,
"rows_produced_per_join": 7,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "1.40",
"prefix_cost": "3.41",
"data_read_per_join": "56"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
} /* query_block */
},
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "2.40"
} /* cost_info */,
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "16"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
} /* query_block */
}
] /* query_specifications */
} /* union_result */,
"order_by_subqueries": [
{
"dependent": true,
"cacheable": false,
"query_block": {
"select_id": 3,
"message": "No tables used"
} /* query_block */
}
] /* order_by_subqueries */
} /* ordering_operation */
} /* query_block */
}
Warnings:
Note 1276 Field or reference 'i' of SELECT #3 was resolved in SELECT #1
Note 1003 (/* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1`) union (/* select#2 */ select `test`.`t2`.`i` AS `i` from `test`.`t2`) order by (/* select#3 */ select `i` limit 1)
# optimizer-time subquery
EXPLAIN SELECT * FROM t1 ORDER BY (SELECT LENGTH(1) FROM t2 LIMIT 1);
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 NULL ALL NULL NULL NULL NULL 7 100.00 NULL
2 SUBQUERY t2 NULL ALL NULL NULL NULL NULL 2 100.00 NULL
Warnings:
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` order by (/* select#2 */ select length(1) from `test`.`t2` limit 1)
EXPLAIN FORMAT=JSON SELECT * FROM t1 ORDER BY (SELECT LENGTH(1) FROM t2 LIMIT 1);
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "3.41"
} /* cost_info */,
"ordering_operation": {
"using_filesort": false,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 7,
"rows_produced_per_join": 7,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "1.40",
"prefix_cost": "3.41",
"data_read_per_join": "56"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */,
"optimized_away_subqueries": [
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "2.40"
} /* cost_info */,
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "16"
} /* cost_info */
} /* table */
} /* query_block */
}
] /* optimized_away_subqueries */
} /* ordering_operation */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` order by (/* select#2 */ select length(1) from `test`.`t2` limit 1)
# subquery in the HAVING clause
EXPLAIN SELECT * FROM t1 HAVING i > ALL (SELECT i FROM t2) OR i < ALL (SELECT i FROM t2);;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 NULL ALL NULL NULL NULL NULL 7 100.00 NULL
3 SUBQUERY t2 NULL ALL NULL NULL NULL NULL 2 100.00 NULL
2 SUBQUERY t2 NULL ALL NULL NULL NULL NULL 2 100.00 NULL
Warnings:
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` having (<not>((`test`.`t1`.`i` <= <max>(/* select#2 */ select `test`.`t2`.`i` from `test`.`t2`))) or <not>((`test`.`t1`.`i` >= <min>(/* select#3 */ select `test`.`t2`.`i` from `test`.`t2`))))
EXPLAIN FORMAT=JSON SELECT * FROM t1 HAVING i > ALL (SELECT i FROM t2) OR i < ALL (SELECT i FROM t2);;
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "3.41"
} /* cost_info */,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 7,
"rows_produced_per_join": 7,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "1.40",
"prefix_cost": "3.41",
"data_read_per_join": "56"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */,
"having_subqueries": [
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 3,
"cost_info": {
"query_cost": "2.40"
} /* cost_info */,
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "16"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
} /* query_block */
},
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "2.40"
} /* cost_info */,
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "16"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
} /* query_block */
}
] /* having_subqueries */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` having (<not>((`test`.`t1`.`i` <= <max>(/* select#2 */ select `test`.`t2`.`i` from `test`.`t2`))) or <not>((`test`.`t1`.`i` >= <min>(/* select#3 */ select `test`.`t2`.`i` from `test`.`t2`))))
# subquery in the GROUP BY clause
EXPLAIN SELECT * FROM t1 GROUP BY i > ALL (SELECT i FROM t2) OR i < ALL (SELECT i FROM t2);;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 NULL ALL NULL NULL NULL NULL 7 100.00 Using temporary; Using filesort
3 DEPENDENT SUBQUERY t2 NULL ALL NULL NULL NULL NULL 2 100.00 Using where
2 DEPENDENT SUBQUERY t2 NULL ALL NULL NULL NULL NULL 2 100.00 Using where
Warnings:
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` group by (<not>(<in_optimizer>(`test`.`t1`.`i`,<exists>(/* select#2 */ select 1 from `test`.`t2` where <if>(outer_field_is_not_null, ((<cache>(`test`.`t1`.`i`) <= `test`.`t2`.`i`) or isnull(`test`.`t2`.`i`)), true) having <if>(outer_field_is_not_null, <is_not_null_test>(`test`.`t2`.`i`), true)))) or <not>(<in_optimizer>(`test`.`t1`.`i`,<exists>(/* select#3 */ select 1 from `test`.`t2` where <if>(outer_field_is_not_null, ((<cache>(`test`.`t1`.`i`) >= `test`.`t2`.`i`) or isnull(`test`.`t2`.`i`)), true) having <if>(outer_field_is_not_null, <is_not_null_test>(`test`.`t2`.`i`), true)))))
EXPLAIN FORMAT=JSON SELECT * FROM t1 GROUP BY i > ALL (SELECT i FROM t2) OR i < ALL (SELECT i FROM t2);;
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "10.41"
} /* cost_info */,
"grouping_operation": {
"using_temporary_table": true,
"using_filesort": true,
"cost_info": {
"sort_cost": "7.00"
} /* cost_info */,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 7,
"rows_produced_per_join": 7,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "1.40",
"prefix_cost": "3.41",
"data_read_per_join": "56"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */,
"group_by_subqueries": [
{
"dependent": true,
"cacheable": false,
"query_block": {
"select_id": 3,
"cost_info": {
"query_cost": "2.40"
} /* cost_info */,
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "16"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */,
"attached_condition": "<if>(outer_field_is_not_null, ((<cache>(`test`.`t1`.`i`) >= `test`.`t2`.`i`) or isnull(`test`.`t2`.`i`)), true)"
} /* table */
} /* query_block */
},
{
"dependent": true,
"cacheable": false,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "2.40"
} /* cost_info */,
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "16"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */,
"attached_condition": "<if>(outer_field_is_not_null, ((<cache>(`test`.`t1`.`i`) <= `test`.`t2`.`i`) or isnull(`test`.`t2`.`i`)), true)"
} /* table */
} /* query_block */
}
] /* group_by_subqueries */
} /* grouping_operation */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` group by (<not>(<in_optimizer>(`test`.`t1`.`i`,<exists>(/* select#2 */ select 1 from `test`.`t2` where <if>(outer_field_is_not_null, ((<cache>(`test`.`t1`.`i`) <= `test`.`t2`.`i`) or isnull(`test`.`t2`.`i`)), true) having <if>(outer_field_is_not_null, <is_not_null_test>(`test`.`t2`.`i`), true)))) or <not>(<in_optimizer>(`test`.`t1`.`i`,<exists>(/* select#3 */ select 1 from `test`.`t2` where <if>(outer_field_is_not_null, ((<cache>(`test`.`t1`.`i`) >= `test`.`t2`.`i`) or isnull(`test`.`t2`.`i`)), true) having <if>(outer_field_is_not_null, <is_not_null_test>(`test`.`t2`.`i`), true)))))
# subquery in the SELECT list
EXPLAIN SELECT (SELECT i + 1 FROM t1 ORDER BY RAND() LIMIT 1), i FROM t1;;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 NULL ALL NULL NULL NULL NULL 7 100.00 NULL
2 UNCACHEABLE SUBQUERY t1 NULL ALL NULL NULL NULL NULL 7 100.00 Using temporary; Using filesort
Warnings:
Note 1003 /* select#1 */ select (/* select#2 */ select (`test`.`t1`.`i` + 1) from `test`.`t1` order by rand() limit 1) AS `(SELECT i + 1 FROM t1 ORDER BY RAND() LIMIT 1)`,`test`.`t1`.`i` AS `i` from `test`.`t1`
EXPLAIN FORMAT=JSON SELECT (SELECT i + 1 FROM t1 ORDER BY RAND() LIMIT 1), i FROM t1;;
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "3.41"
} /* cost_info */,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 7,
"rows_produced_per_join": 7,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "1.40",
"prefix_cost": "3.41",
"data_read_per_join": "56"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */,
"select_list_subqueries": [
{
"dependent": false,
"cacheable": false,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "3.41"
} /* cost_info */,
"ordering_operation": {
"using_temporary_table": true,
"using_filesort": true,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 7,
"rows_produced_per_join": 7,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "1.40",
"prefix_cost": "3.41",
"data_read_per_join": "56"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
} /* ordering_operation */
} /* query_block */
}
] /* select_list_subqueries */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select (/* select#2 */ select (`test`.`t1`.`i` + 1) from `test`.`t1` order by rand() limit 1) AS `(SELECT i + 1 FROM t1 ORDER BY RAND() LIMIT 1)`,`test`.`t1`.`i` AS `i` from `test`.`t1`
DROP TABLE t1, t2, t3, t4;
# derived table that is optimized out
CREATE TABLE t1 (i INT);
EXPLAIN SELECT 1 FROM (SELECT 1 AS x FROM t1) tt WHERE x;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL NULL NULL no matching row in const table
Warnings:
Note 1003 /* select#1 */ select 1 AS `1` from `test`.`t1` where 1
EXPLAIN FORMAT= JSON SELECT 1 FROM (SELECT 1 AS x FROM t1) tt WHERE x;
EXPLAIN
{
"query_block": {
"select_id": 1,
"message": "no matching row in const table"
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select 1 AS `1` from `test`.`t1` where 1
DROP TABLE t1;
# complex subqueries
CREATE TABLE t1 (a INT, b INT);
CREATE TABLE t2 (c INT, d INT);
CREATE TABLE t3 (e INT);
CREATE TABLE t4 (f INT, g INT);
INSERT INTO t1 VALUES (1,10), (2,10);
INSERT INTO t2 VALUES (2,10), (2,20);
INSERT INTO t3 VALUES (10), (30);
INSERT INTO t4 VALUES (2,10), (2,10);
EXPLAIN SELECT * FROM t1 WHERE t1.a IN (SELECT c FROM t2 WHERE (SELECT e FROM t3) < SOME(SELECT e FROM t3 WHERE t1.b));;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 NULL ALL NULL NULL NULL NULL 2 100.00 Using where
1 PRIMARY t2 NULL ALL NULL NULL NULL NULL 2 50.00 Using where; FirstMatch(t1); Using join buffer (Block Nested Loop)
4 DEPENDENT SUBQUERY t3 NULL ALL NULL NULL NULL NULL 2 100.00 Using where
3 SUBQUERY t3 NULL ALL NULL NULL NULL NULL 2 100.00 NULL
Warnings:
Note 1276 Field or reference 'test.t1.b' of SELECT #4 was resolved in SELECT #1
Note 1003 /* select#1 */ select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` semi join (`test`.`t2`) where ((`test`.`t2`.`c` = `test`.`t1`.`a`) and <nop>(<in_optimizer>((/* select#3 */ select `test`.`t3`.`e` from `test`.`t3`),<exists>(/* select#4 */ select 1 from `test`.`t3` where (`test`.`t1`.`b` and <if>(outer_field_is_not_null, ((<cache>((/* select#3 */ select `test`.`t3`.`e` from `test`.`t3`)) < `test`.`t3`.`e`) or isnull(`test`.`t3`.`e`)), true)) having <if>(outer_field_is_not_null, <is_not_null_test>(`test`.`t3`.`e`), true)))))
EXPLAIN FORMAT=JSON SELECT * FROM t1 WHERE t1.a IN (SELECT c FROM t2 WHERE (SELECT e FROM t3) < SOME(SELECT e FROM t3 WHERE t1.b));;
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "5.21"
} /* cost_info */,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "32"
} /* cost_info */,
"used_columns": [
"a",
"b"
] /* used_columns */,
"attached_condition": "<nop>(<in_optimizer>((/* select#3 */ select `test`.`t3`.`e` from `test`.`t3`),<exists>(/* select#4 */ select 1 from `test`.`t3` where (`test`.`t1`.`b` and <if>(outer_field_is_not_null, ((<cache>((/* select#3 */ select `test`.`t3`.`e` from `test`.`t3`)) < `test`.`t3`.`e`) or isnull(`test`.`t3`.`e`)), true)) having <if>(outer_field_is_not_null, <is_not_null_test>(`test`.`t3`.`e`), true))))",
"attached_subqueries": [
{
"dependent": true,
"cacheable": false,
"query_block": {
"select_id": 4,
"cost_info": {
"query_cost": "2.40"
} /* cost_info */,
"table": {
"table_name": "t3",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "16"
} /* cost_info */,
"used_columns": [
"e"
] /* used_columns */,
"attached_condition": "(`test`.`t1`.`b` and <if>(outer_field_is_not_null, ((<cache>((/* select#3 */ select `test`.`t3`.`e` from `test`.`t3`)) < `test`.`t3`.`e`) or isnull(`test`.`t3`.`e`)), true))"
} /* table */
} /* query_block */
},
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 3,
"cost_info": {
"query_cost": "2.40"
} /* cost_info */,
"table": {
"table_name": "t3",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "16"
} /* cost_info */,
"used_columns": [
"e"
] /* used_columns */
} /* table */
} /* query_block */
}
] /* attached_subqueries */
} /* table */
},
{
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "50.00",
"first_match": "t1",
"using_join_buffer": "Block Nested Loop",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "5.21",
"data_read_per_join": "32"
} /* cost_info */,
"used_columns": [
"c"
] /* used_columns */,
"attached_condition": "(`test`.`t2`.`c` = `test`.`t1`.`a`)"
} /* table */
}
] /* nested_loop */
} /* query_block */
}
Warnings:
Note 1276 Field or reference 'test.t1.b' of SELECT #4 was resolved in SELECT #1
Note 1003 /* select#1 */ select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` semi join (`test`.`t2`) where ((`test`.`t2`.`c` = `test`.`t1`.`a`) and <nop>(<in_optimizer>((/* select#3 */ select `test`.`t3`.`e` from `test`.`t3`),<exists>(/* select#4 */ select 1 from `test`.`t3` where (`test`.`t1`.`b` and <if>(outer_field_is_not_null, ((<cache>((/* select#3 */ select `test`.`t3`.`e` from `test`.`t3`)) < `test`.`t3`.`e`) or isnull(`test`.`t3`.`e`)), true)) having <if>(outer_field_is_not_null, <is_not_null_test>(`test`.`t3`.`e`), true)))))
DROP TABLE t1, t2, t3, t4;
# semi-join materialization (if enabled)
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (1), (1), (1), (1), (1), (1), (1), (1), (1), (1), (1), (1);
CREATE TABLE t2 (a INT) SELECT * FROM t1;
CREATE TABLE t3 (a INT) SELECT * FROM t1;
CREATE TABLE t4 (a INT) SELECT * FROM t1;
EXPLAIN FORMAT=JSON
SELECT * FROM t1
WHERE t1.a IN (SELECT t2.a FROM t2 WHERE t2.a > 0) AND
t1.a IN (SELECT t3.a FROM t3 WHERE t3.a IN
(SELECT t4.a FROM t4 WHERE a > 0));
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "35.44"
} /* cost_info */,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 12,
"rows_produced_per_join": 12,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.02",
"eval_cost": "2.40",
"prefix_cost": "4.42",
"data_read_per_join": "96"
} /* cost_info */,
"used_columns": [
"a"
] /* used_columns */,
"attached_condition": "((`test`.`t1`.`a` is not null) and (`test`.`t1`.`a` is not null))"
} /* table */
},
{
"table": {
"table_name": "<subquery3>",
"access_type": "eq_ref",
"key": "<auto_key>",
"key_length": "5",
"ref": [
"test.t1.a"
] /* ref */,
"rows_examined_per_scan": 1,
"materialized_from_subquery": {
"using_temporary_table": true,
"query_block": {
"nested_loop": [
{
"table": {
"table_name": "t4",
"access_type": "ALL",
"rows_examined_per_scan": 12,
"rows_produced_per_join": 3,
"filtered": "33.33",
"cost_info": {
"read_cost": "3.62",
"eval_cost": "0.80",
"prefix_cost": "4.42",
"data_read_per_join": "31"
} /* cost_info */,
"used_columns": [
"a"
] /* used_columns */,
"attached_condition": "(`test`.`t4`.`a` > 0)"
} /* table */
},
{
"table": {
"table_name": "t3",
"access_type": "ALL",
"rows_examined_per_scan": 12,
"rows_produced_per_join": 4,
"filtered": "10.00",
"using_join_buffer": "Block Nested Loop",
"cost_info": {
"read_cost": "2.02",
"eval_cost": "0.96",
"prefix_cost": "16.04",
"data_read_per_join": "38"
} /* cost_info */,
"used_columns": [
"a"
] /* used_columns */,
"attached_condition": "(`test`.`t3`.`a` = `test`.`t4`.`a`)"
} /* table */
}
] /* nested_loop */
} /* query_block */
} /* materialized_from_subquery */
} /* table */
},
{
"table": {
"table_name": "<subquery2>",
"access_type": "eq_ref",
"key": "<auto_key>",
"key_length": "5",
"ref": [
"test.t1.a"
] /* ref */,
"rows_examined_per_scan": 1,
"materialized_from_subquery": {
"using_temporary_table": true,
"query_block": {
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 12,
"rows_produced_per_join": 3,
"filtered": "33.33",
"cost_info": {
"read_cost": "3.62",
"eval_cost": "0.80",
"prefix_cost": "4.42",
"data_read_per_join": "31"
} /* cost_info */,
"used_columns": [
"a"
] /* used_columns */,
"attached_condition": "(`test`.`t2`.`a` > 0)"
} /* table */
} /* query_block */
} /* materialized_from_subquery */
} /* table */
}
] /* nested_loop */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` semi join (`test`.`t4` join `test`.`t3`) semi join (`test`.`t2`) where ((`<subquery3>`.`a` = `test`.`t1`.`a`) and (`<subquery2>`.`a` = `test`.`t1`.`a`) and (`test`.`t3`.`a` = `test`.`t4`.`a`) and (`test`.`t4`.`a` > 0) and (`test`.`t2`.`a` > 0))
DROP TABLE t1, t2, t3, t4;
# the same subquery is associated with two different JOIN_TABs
CREATE TABLE t1 (
i1 INTEGER NOT NULL,
c1 VARCHAR(1) NOT NULL
) ENGINE=InnoDB;
INSERT INTO t1 VALUES (2,'w');
CREATE TABLE t2 (
i1 INTEGER NOT NULL,
c1 VARCHAR(1) NOT NULL,
c2 VARCHAR(1) NOT NULL,
KEY (c1, i1)
) ENGINE=InnoDB;
INSERT INTO t2 VALUES (8,'d','d');
INSERT INTO t2 VALUES (4,'v','v');
CREATE TABLE t3 (
c1 VARCHAR(1) NOT NULL
) ENGINE=InnoDB;
INSERT INTO t3 VALUES ('v');
EXPLAIN FORMAT=json
SELECT i1
FROM t1
WHERE EXISTS (SELECT t2.c1
FROM (t2 INNER JOIN t3 ON (t3.c1 = t2.c1))
WHERE t2.c2 != t1.c1 AND t2.c2 = (SELECT MIN(t3.c1)
FROM t3));
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "1.20"
} /* cost_info */,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 1,
"rows_produced_per_join": 1,
"filtered": "100.00",
"cost_info": {
"read_cost": "1.00",
"eval_cost": "0.20",
"prefix_cost": "1.20",
"data_read_per_join": "8"
} /* cost_info */,
"used_columns": [
"i1",
"c1"
] /* used_columns */,
"attached_condition": "exists(/* select#2 */ select `test`.`t2`.`c1` from `test`.`t2` join `test`.`t3` where ((`test`.`t2`.`c1` = `test`.`t3`.`c1`) and (`test`.`t2`.`c2` = (/* select#3 */ select min(`test`.`t3`.`c1`) from `test`.`t3`)) and ((/* select#3 */ select min(`test`.`t3`.`c1`) from `test`.`t3`) <> `test`.`t1`.`c1`)))",
"attached_subqueries": [
{
"dependent": true,
"cacheable": false,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "2.40"
} /* cost_info */,
"nested_loop": [
{
"table": {
"table_name": "t3",
"access_type": "ALL",
"rows_examined_per_scan": 1,
"rows_produced_per_join": 1,
"filtered": "100.00",
"cost_info": {
"read_cost": "1.00",
"eval_cost": "0.20",
"prefix_cost": "1.20",
"data_read_per_join": "8"
} /* cost_info */,
"used_columns": [
"c1"
] /* used_columns */,
"attached_condition": "((/* select#3 */ select min(`test`.`t3`.`c1`) from `test`.`t3`) <> `test`.`t1`.`c1`)",
"attached_subqueries": [
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 3,
"cost_info": {
"query_cost": "1.20"
} /* cost_info */,
"table": {
"table_name": "t3",
"access_type": "ALL",
"rows_examined_per_scan": 1,
"rows_produced_per_join": 1,
"filtered": "100.00",
"cost_info": {
"read_cost": "1.00",
"eval_cost": "0.20",
"prefix_cost": "1.20",
"data_read_per_join": "8"
} /* cost_info */,
"used_columns": [
"c1"
] /* used_columns */
} /* table */
} /* query_block */
}
] /* attached_subqueries */
} /* table */
},
{
"table": {
"table_name": "t2",
"access_type": "ref",
"possible_keys": [
"c1"
] /* possible_keys */,
"key": "c1",
"used_key_parts": [
"c1"
] /* used_key_parts */,
"key_length": "3",
"ref": [
"test.t3.c1"
] /* ref */,
"rows_examined_per_scan": 1,
"rows_produced_per_join": 0,
"filtered": "50.00",
"cost_info": {
"read_cost": "1.00",
"eval_cost": "0.10",
"prefix_cost": "2.40",
"data_read_per_join": "8"
} /* cost_info */,
"used_columns": [
"c1",
"c2"
] /* used_columns */,
"attached_condition": "(`test`.`t2`.`c2` = (/* select#3 */ select min(`test`.`t3`.`c1`) from `test`.`t3`))",
"attached_subqueries": [
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 3,
"cost_info": {
"query_cost": "1.20"
} /* cost_info */,
"table": {
"table_name": "t3",
"access_type": "ALL",
"rows_examined_per_scan": 1,
"rows_produced_per_join": 1,
"filtered": "100.00",
"cost_info": {
"read_cost": "1.00",
"eval_cost": "0.20",
"prefix_cost": "1.20",
"data_read_per_join": "8"
} /* cost_info */,
"used_columns": [
"c1"
] /* used_columns */
} /* table */
} /* query_block */
}
] /* attached_subqueries */
} /* table */
}
] /* nested_loop */
} /* query_block */
}
] /* attached_subqueries */
} /* table */
} /* query_block */
}
Warnings:
Note 1276 Field or reference 'test.t1.c1' of SELECT #2 was resolved in SELECT #1
Note 1003 /* select#1 */ select `test`.`t1`.`i1` AS `i1` from `test`.`t1` where exists(/* select#2 */ select `test`.`t2`.`c1` from `test`.`t2` join `test`.`t3` where ((`test`.`t2`.`c1` = `test`.`t3`.`c1`) and (`test`.`t2`.`c2` = (/* select#3 */ select min(`test`.`t3`.`c1`) from `test`.`t3`)) and ((/* select#3 */ select min(`test`.`t3`.`c1`) from `test`.`t3`) <> `test`.`t1`.`c1`)))
DROP TABLE t1, t2, t3;
# multiple materialization groups
CREATE TABLE t1 (c_key INT, KEY c_key (c_key));
INSERT INTO t1 VALUES (1), (2), (3);
CREATE TABLE t2 (c INT, c_key INT);
INSERT INTO t2 VALUES (8,5),(4,5),(8,1);
CREATE TABLE t3 LIKE t1;
INSERT INTO t3 SELECT * FROM t1;
CREATE TABLE t4 LIKE t2;
INSERT INTO t4 SELECT * FROM t2;
CREATE TABLE t5 (c INT);
INSERT INTO t5 VALUES (1), (2), (3);
# This should show two materialization groups where applicable
EXPLAIN SELECT * FROM t5
WHERE c IN (SELECT t2.c FROM t1 JOIN t2 ON t2.c_key = t1.c_key)
AND c IN (SELECT t4.c FROM t3 JOIN t4 ON t4.c_key = t3.c_key);
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t5 NULL ALL NULL NULL NULL NULL 3 100.00 Start temporary
1 SIMPLE t2 NULL ALL NULL NULL NULL NULL 3 33.33 Using where; Using join buffer (Block Nested Loop)
1 SIMPLE t1 NULL index c_key c_key 5 NULL 3 33.33 Using where; Using index; Using join buffer (Block Nested Loop)
1 SIMPLE t4 NULL ALL NULL NULL NULL NULL 3 33.33 Using where; Using join buffer (Block Nested Loop)
1 SIMPLE t3 NULL ref c_key c_key 5 test.t4.c_key 1 100.00 Using index; End temporary
Warnings:
Note 1003 /* select#1 */ select `test`.`t5`.`c` AS `c` from `test`.`t5` semi join (`test`.`t1` join `test`.`t2`) semi join (`test`.`t3` join `test`.`t4`) where ((`test`.`t3`.`c_key` = `test`.`t4`.`c_key`) and (`test`.`t1`.`c_key` = `test`.`t2`.`c_key`) and (`test`.`t2`.`c` = `test`.`t5`.`c`) and (`test`.`t4`.`c` = `test`.`t5`.`c`))
EXPLAIN FORMAT=JSON SELECT * FROM t5
WHERE c IN (SELECT t2.c FROM t1 JOIN t2 ON t2.c_key = t1.c_key)
AND c IN (SELECT t4.c FROM t3 JOIN t4 ON t4.c_key = t3.c_key);
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "20.82"
} /* cost_info */,
"duplicates_removal": {
"using_temporary_table": true,
"nested_loop": [
{
"table": {
"table_name": "t5",
"access_type": "ALL",
"rows_examined_per_scan": 3,
"rows_produced_per_join": 3,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "0.60",
"prefix_cost": "2.61",
"data_read_per_join": "24"
} /* cost_info */,
"used_columns": [
"c"
] /* used_columns */
} /* table */
},
{
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 3,
"rows_produced_per_join": 3,
"filtered": "33.33",
"using_join_buffer": "Block Nested Loop",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "0.60",
"prefix_cost": "6.41",
"data_read_per_join": "48"
} /* cost_info */,
"used_columns": [
"c",
"c_key"
] /* used_columns */,
"attached_condition": "(`test`.`t2`.`c` = `test`.`t5`.`c`)"
} /* table */
},
{
"table": {
"table_name": "t1",
"access_type": "index",
"possible_keys": [
"c_key"
] /* possible_keys */,
"key": "c_key",
"used_key_parts": [
"c_key"
] /* used_key_parts */,
"key_length": "5",
"rows_examined_per_scan": 3,
"rows_produced_per_join": 3,
"filtered": "33.33",
"using_index": true,
"using_join_buffer": "Block Nested Loop",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "0.60",
"prefix_cost": "12.22",
"data_read_per_join": "24"
} /* cost_info */,
"used_columns": [
"c_key"
] /* used_columns */,
"attached_condition": "(`test`.`t1`.`c_key` = `test`.`t2`.`c_key`)"
} /* table */
},
{
"table": {
"table_name": "t4",
"access_type": "ALL",
"rows_examined_per_scan": 3,
"rows_produced_per_join": 3,
"filtered": "33.33",
"using_join_buffer": "Block Nested Loop",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "0.60",
"prefix_cost": "16.02",
"data_read_per_join": "48"
} /* cost_info */,
"used_columns": [
"c",
"c_key"
] /* used_columns */,
"attached_condition": "((`test`.`t4`.`c` = `test`.`t5`.`c`) and (`test`.`t4`.`c_key` is not null))"
} /* table */
},
{
"table": {
"table_name": "t3",
"access_type": "ref",
"possible_keys": [
"c_key"
] /* possible_keys */,
"key": "c_key",
"used_key_parts": [
"c_key"
] /* used_key_parts */,
"key_length": "5",
"ref": [
"test.t4.c_key"
] /* ref */,
"rows_examined_per_scan": 1,
"rows_produced_per_join": 3,
"filtered": "100.00",
"using_index": true,
"cost_info": {
"read_cost": "3.00",
"eval_cost": "0.60",
"prefix_cost": "20.82",
"data_read_per_join": "24"
} /* cost_info */,
"used_columns": [
"c_key"
] /* used_columns */
} /* table */
}
] /* nested_loop */
} /* duplicates_removal */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select `test`.`t5`.`c` AS `c` from `test`.`t5` semi join (`test`.`t1` join `test`.`t2`) semi join (`test`.`t3` join `test`.`t4`) where ((`test`.`t3`.`c_key` = `test`.`t4`.`c_key`) and (`test`.`t1`.`c_key` = `test`.`t2`.`c_key`) and (`test`.`t2`.`c` = `test`.`t5`.`c`) and (`test`.`t4`.`c` = `test`.`t5`.`c`))
DROP TABLE t1, t2, t3, t4, t5;
CREATE TABLE t1 (i INT);
CREATE TABLE t2 (i INT);
CREATE TABLE t3 (i INT);
INSERT INTO t1 VALUES (1);
INSERT INTO t2 VALUES (1);
INSERT INTO t3 VALUES (1);
# Subqueries in UPDATE values list
EXPLAIN UPDATE t1 SET i=(SELECT i FROM t2);
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 UPDATE t1 NULL ALL NULL NULL NULL NULL 1 100.00 NULL
2 SUBQUERY t2 NULL system NULL NULL NULL NULL 1 100.00 NULL
EXPLAIN FORMAT=JSON UPDATE t1 SET i=(SELECT i FROM t2);
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"update": true,
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 1,
"filtered": "100.00"
} /* table */,
"update_value_subqueries": [
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "1.00"
} /* cost_info */,
"table": {
"table_name": "t2",
"access_type": "system",
"rows_examined_per_scan": 1,
"rows_produced_per_join": 1,
"filtered": "100.00",
"cost_info": {
"read_cost": "0.00",
"eval_cost": "0.20",
"prefix_cost": "0.00",
"data_read_per_join": "8"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
} /* query_block */
}
] /* update_value_subqueries */
} /* query_block */
}
EXPLAIN UPDATE t1, t2 SET t1.i=(SELECT i FROM t3);
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 UPDATE t1 NULL system NULL NULL NULL NULL 1 100.00 NULL
1 PRIMARY t2 NULL system NULL NULL NULL NULL 1 100.00 NULL
2 SUBQUERY t3 NULL system NULL NULL NULL NULL 1 100.00 NULL
EXPLAIN FORMAT=JSON UPDATE t1, t2 SET t1.i=(SELECT i FROM t3);
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "1.00"
} /* cost_info */,
"nested_loop": [
{
"table": {
"update": true,
"table_name": "t1",
"access_type": "system",
"rows_examined_per_scan": 1,
"rows_produced_per_join": 1,
"filtered": "100.00",
"cost_info": {
"read_cost": "0.00",
"eval_cost": "0.20",
"prefix_cost": "0.00",
"data_read_per_join": "8"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
},
{
"table": {
"table_name": "t2",
"access_type": "system",
"rows_examined_per_scan": 1,
"rows_produced_per_join": 1,
"filtered": "100.00",
"cost_info": {
"read_cost": "0.00",
"eval_cost": "0.20",
"prefix_cost": "0.00",
"data_read_per_join": "8"
} /* cost_info */
} /* table */
}
] /* nested_loop */,
"update_value_subqueries": [
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "1.00"
} /* cost_info */,
"table": {
"table_name": "t3",
"access_type": "system",
"rows_examined_per_scan": 1,
"rows_produced_per_join": 1,
"filtered": "100.00",
"cost_info": {
"read_cost": "0.00",
"eval_cost": "0.20",
"prefix_cost": "0.00",
"data_read_per_join": "8"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
} /* query_block */
}
] /* update_value_subqueries */
} /* query_block */
}
# INSERT ... ON DUPLICATE KEY UPDATE x=(SELECT ...) value list
EXPLAIN INSERT INTO t1 (i)
SELECT i FROM t2 ON DUPLICATE KEY UPDATE i=(SELECT i FROM t2);
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 INSERT t1 NULL ALL NULL NULL NULL NULL NULL NULL NULL
1 PRIMARY t2 NULL system NULL NULL NULL NULL 1 100.00 NULL
2 SUBQUERY t2 NULL system NULL NULL NULL NULL 1 100.00 NULL
EXPLAIN FORMAT=JSON INSERT INTO t1 (i)
SELECT i FROM t2 ON DUPLICATE KEY UPDATE i=(SELECT i FROM t2);
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "1.00"
} /* cost_info */,
"table": {
"insert": true,
"table_name": "t1",
"access_type": "ALL"
} /* table */,
"insert_from": {
"table": {
"table_name": "t2",
"access_type": "system",
"rows_examined_per_scan": 1,
"rows_produced_per_join": 1,
"filtered": "100.00",
"cost_info": {
"read_cost": "0.00",
"eval_cost": "0.20",
"prefix_cost": "0.00",
"data_read_per_join": "8"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
} /* insert_from */,
"update_value_subqueries": [
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "1.00"
} /* cost_info */,
"table": {
"table_name": "t2",
"access_type": "system",
"rows_examined_per_scan": 1,
"rows_produced_per_join": 1,
"filtered": "100.00",
"cost_info": {
"read_cost": "0.00",
"eval_cost": "0.20",
"prefix_cost": "0.00",
"data_read_per_join": "8"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
} /* query_block */
}
] /* update_value_subqueries */
} /* query_block */
}
EXPLAIN INSERT INTO t1 VALUES (1)
ON DUPLICATE KEY UPDATE i = (SELECT i FROM t2);
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 INSERT t1 NULL ALL NULL NULL NULL NULL NULL NULL NULL
2 SUBQUERY t2 NULL system NULL NULL NULL NULL 1 100.00 NULL
EXPLAIN FORMAT=JSON INSERT INTO t1 VALUES (1)
ON DUPLICATE KEY UPDATE i = (SELECT i FROM t2);
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"insert": true,
"table_name": "t1",
"access_type": "ALL"
} /* table */,
"update_value_subqueries": [
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "1.00"
} /* cost_info */,
"table": {
"table_name": "t2",
"access_type": "system",
"rows_examined_per_scan": 1,
"rows_produced_per_join": 1,
"filtered": "100.00",
"cost_info": {
"read_cost": "0.00",
"eval_cost": "0.20",
"prefix_cost": "0.00",
"data_read_per_join": "8"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
} /* query_block */
}
] /* update_value_subqueries */
} /* query_block */
}
# Subqueries in INSERT VALUES tuples:
EXPLAIN INSERT INTO t3 VALUES((SELECT i FROM t1)), ((SELECT i FROM t2));
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 INSERT t3 NULL ALL NULL NULL NULL NULL NULL NULL NULL
3 SUBQUERY t2 NULL system NULL NULL NULL NULL 1 100.00 NULL
2 SUBQUERY t1 NULL system NULL NULL NULL NULL 1 100.00 NULL
EXPLAIN FORMAT=JSON INSERT INTO t3 VALUES((SELECT i FROM t1)), ((SELECT i FROM t2));
EXPLAIN
{
"query_block": {
"select_id": 1,
"table": {
"insert": true,
"table_name": "t3",
"access_type": "ALL"
} /* table */,
"optimized_away_subqueries": [
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 3,
"cost_info": {
"query_cost": "1.00"
} /* cost_info */,
"table": {
"table_name": "t2",
"access_type": "system",
"rows_examined_per_scan": 1,
"rows_produced_per_join": 1,
"filtered": "100.00",
"cost_info": {
"read_cost": "0.00",
"eval_cost": "0.20",
"prefix_cost": "0.00",
"data_read_per_join": "8"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
} /* query_block */
},
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "1.00"
} /* cost_info */,
"table": {
"table_name": "t1",
"access_type": "system",
"rows_examined_per_scan": 1,
"rows_produced_per_join": 1,
"filtered": "100.00",
"cost_info": {
"read_cost": "0.00",
"eval_cost": "0.20",
"prefix_cost": "0.00",
"data_read_per_join": "8"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */
} /* query_block */
}
] /* optimized_away_subqueries */
} /* query_block */
}
DROP TABLE t1, t2, t3;
# Various queries
EXPLAIN SELECT a, b FROM
(SELECT 1 AS a, 2 AS b
UNION ALL
SELECT 1 AS a, 2 AS b) t1
GROUP BY a
ORDER BY b DESC;
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 PRIMARY <derived2> NULL ALL NULL NULL NULL NULL 2 100.00 Using temporary; Using filesort
2 DERIVED NULL NULL NULL NULL NULL NULL NULL NULL NULL No tables used
3 UNION NULL NULL NULL NULL NULL NULL NULL NULL NULL No tables used
Warnings:
Note 1003 /* select#1 */ select `t1`.`a` AS `a`,`t1`.`b` AS `b` from (/* select#2 */ select 1 AS `a`,2 AS `b` union all /* select#3 */ select 1 AS `a`,2 AS `b`) `t1` group by `t1`.`a` order by `t1`.`b` desc
EXPLAIN FORMAT=JSON SELECT a, b FROM
(SELECT 1 AS a, 2 AS b
UNION ALL
SELECT 1 AS a, 2 AS b) t1
GROUP BY a
ORDER BY b DESC;
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "10.50"
} /* cost_info */,
"ordering_operation": {
"using_filesort": true,
"grouping_operation": {
"using_temporary_table": true,
"using_filesort": false,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "10.10",
"eval_cost": "0.40",
"prefix_cost": "10.50",
"data_read_per_join": "48"
} /* cost_info */,
"used_columns": [
"a",
"b"
] /* used_columns */,
"materialized_from_subquery": {
"using_temporary_table": true,
"dependent": false,
"cacheable": true,
"query_block": {
"union_result": {
"using_temporary_table": false,
"query_specifications": [
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 2,
"message": "No tables used"
} /* query_block */
},
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 3,
"message": "No tables used"
} /* query_block */
}
] /* query_specifications */
} /* union_result */
} /* query_block */
} /* materialized_from_subquery */
} /* table */
} /* grouping_operation */
} /* ordering_operation */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select `t1`.`a` AS `a`,`t1`.`b` AS `b` from (/* select#2 */ select 1 AS `a`,2 AS `b` union all /* select#3 */ select 1 AS `a`,2 AS `b`) `t1` group by `t1`.`a` order by `t1`.`b` desc
#
CREATE TABLE t1(a INT, b INT);
INSERT INTO t1 VALUES (), ();
EXPLAIN SELECT 1 FROM t1 GROUP BY GREATEST(t1.a, (SELECT 1 FROM (SELECT t1.b FROM t1, t1 t2 ORDER BY t1.a, t1.a LIMIT 1) AS d));
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 NULL ALL NULL NULL NULL NULL 2 100.00 Using temporary; Using filesort
2 SUBQUERY <derived3> NULL system NULL NULL NULL NULL 1 100.00 NULL
3 DERIVED t1 NULL ALL NULL NULL NULL NULL 2 100.00 Using temporary; Using filesort
3 DERIVED t2 NULL ALL NULL NULL NULL NULL 2 100.00 Using join buffer (Block Nested Loop)
Warnings:
Note 1003 /* select#1 */ select 1 AS `1` from `test`.`t1` group by greatest(`test`.`t1`.`a`,(/* select#2 */ select 1 from dual))
EXPLAIN FORMAT=JSON SELECT 1 FROM t1 GROUP BY GREATEST(t1.a, (SELECT 1 FROM (SELECT t1.b FROM t1, t1 t2 ORDER BY t1.a, t1.a LIMIT 1) AS d));
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "4.40"
} /* cost_info */,
"grouping_operation": {
"using_temporary_table": true,
"using_filesort": true,
"cost_info": {
"sort_cost": "2.00"
} /* cost_info */,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "32"
} /* cost_info */,
"used_columns": [
"a"
] /* used_columns */
} /* table */,
"group_by_subqueries": [
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "1.00"
} /* cost_info */,
"table": {
"table_name": "d",
"access_type": "system",
"rows_examined_per_scan": 1,
"rows_produced_per_join": 1,
"filtered": "100.00",
"cost_info": {
"read_cost": "0.00",
"eval_cost": "0.20",
"prefix_cost": "0.00",
"data_read_per_join": "16"
} /* cost_info */,
"used_columns": [
"b"
] /* used_columns */,
"materialized_from_subquery": {
"using_temporary_table": true,
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 3,
"cost_info": {
"query_cost": "5.21"
} /* cost_info */,
"ordering_operation": {
"using_temporary_table": true,
"using_filesort": true,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "32"
} /* cost_info */,
"used_columns": [
"a",
"b"
] /* used_columns */
} /* table */
},
{
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 4,
"filtered": "100.00",
"using_join_buffer": "Block Nested Loop",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.80",
"prefix_cost": "5.21",
"data_read_per_join": "64"
} /* cost_info */
} /* table */
}
] /* nested_loop */
} /* ordering_operation */
} /* query_block */
} /* materialized_from_subquery */
} /* table */
} /* query_block */
}
] /* group_by_subqueries */
} /* grouping_operation */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select 1 AS `1` from `test`.`t1` group by greatest(`test`.`t1`.`a`,(/* select#2 */ select 1 from dual))
DROP TABLE t1;
#
CREATE TABLE t1(f1 INT);
INSERT INTO t1 VALUES (1),(1);
EXPLAIN SELECT 1 FROM t1 WHERE (SELECT (SELECT 1 FROM t1 GROUP BY f1));
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 NULL ALL NULL NULL NULL NULL 2 100.00 NULL
3 SUBQUERY t1 NULL ALL NULL NULL NULL NULL 2 100.00 Using temporary; Using filesort
Warnings:
Note 1249 Select 2 was reduced during optimization
Note 1003 /* select#1 */ select 1 AS `1` from `test`.`t1` where 1
EXPLAIN FORMAT=JSON SELECT 1 FROM t1 WHERE (SELECT (SELECT 1 FROM t1 GROUP BY f1));
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "2.40"
} /* cost_info */,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "16"
} /* cost_info */
} /* table */,
"optimized_away_subqueries": [
{
"dependent": false,
"cacheable": true,
"query_block": {
"select_id": 3,
"cost_info": {
"query_cost": "4.40"
} /* cost_info */,
"grouping_operation": {
"using_temporary_table": true,
"using_filesort": true,
"cost_info": {
"sort_cost": "2.00"
} /* cost_info */,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "16"
} /* cost_info */,
"used_columns": [
"f1"
] /* used_columns */
} /* table */
} /* grouping_operation */
} /* query_block */
}
] /* optimized_away_subqueries */
} /* query_block */
}
Warnings:
Note 1249 Select 2 was reduced during optimization
Note 1003 /* select#1 */ select 1 AS `1` from `test`.`t1` where 1
DROP TABLE t1;
#
CREATE TABLE t1 (i INT);
CREATE TABLE t2 (i INT, j INT);
INSERT INTO t1 VALUES (1), (2), (3), (4), (5), (6), (7), (8), (9), (10);
INSERT INTO t2 SELECT i, i * 10 FROM t1;
EXPLAIN SELECT * FROM t1 ORDER BY (SELECT t2.j FROM t2 WHERE t2.i = t1.i);
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 NULL ALL NULL NULL NULL NULL 10 100.00 Using filesort
2 DEPENDENT SUBQUERY t2 NULL ALL NULL NULL NULL NULL 10 10.00 Using where
Warnings:
Note 1276 Field or reference 'test.t1.i' of SELECT #2 was resolved in SELECT #1
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` order by (/* select#2 */ select `test`.`t2`.`j` from `test`.`t2` where (`test`.`t2`.`i` = `test`.`t1`.`i`))
EXPLAIN FORMAT=JSON SELECT * FROM t1 ORDER BY (SELECT t2.j FROM t2 WHERE t2.i = t1.i);
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "4.02"
} /* cost_info */,
"ordering_operation": {
"using_filesort": true,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 10,
"rows_produced_per_join": 10,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.02",
"eval_cost": "2.00",
"prefix_cost": "4.02",
"data_read_per_join": "80"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */,
"order_by_subqueries": [
{
"dependent": true,
"cacheable": false,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "4.02"
} /* cost_info */,
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 10,
"rows_produced_per_join": 1,
"filtered": "10.00",
"cost_info": {
"read_cost": "2.02",
"eval_cost": "0.20",
"prefix_cost": "4.02",
"data_read_per_join": "16"
} /* cost_info */,
"used_columns": [
"i",
"j"
] /* used_columns */,
"attached_condition": "(`test`.`t2`.`i` = `test`.`t1`.`i`)"
} /* table */
} /* query_block */
}
] /* order_by_subqueries */
} /* ordering_operation */
} /* query_block */
}
Warnings:
Note 1276 Field or reference 'test.t1.i' of SELECT #2 was resolved in SELECT #1
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` order by (/* select#2 */ select `test`.`t2`.`j` from `test`.`t2` where (`test`.`t2`.`i` = `test`.`t1`.`i`))
EXPLAIN SELECT * FROM t1 GROUP BY (SELECT t2.j FROM t2 WHERE t2.i = t1.i);
id select_type table partitions type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 NULL ALL NULL NULL NULL NULL 10 100.00 Using temporary; Using filesort
2 DEPENDENT SUBQUERY t2 NULL ALL NULL NULL NULL NULL 10 10.00 Using where
Warnings:
Note 1276 Field or reference 'test.t1.i' of SELECT #2 was resolved in SELECT #1
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` group by (/* select#2 */ select `test`.`t2`.`j` from `test`.`t2` where (`test`.`t2`.`i` = `test`.`t1`.`i`))
EXPLAIN FORMAT=JSON SELECT * FROM t1 GROUP BY (SELECT t2.j FROM t2 WHERE t2.i = t1.i);
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "4.02"
} /* cost_info */,
"grouping_operation": {
"using_temporary_table": true,
"using_filesort": true,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 10,
"rows_produced_per_join": 10,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.02",
"eval_cost": "2.00",
"prefix_cost": "4.02",
"data_read_per_join": "80"
} /* cost_info */,
"used_columns": [
"i"
] /* used_columns */
} /* table */,
"group_by_subqueries": [
{
"dependent": true,
"cacheable": false,
"query_block": {
"select_id": 2,
"cost_info": {
"query_cost": "4.02"
} /* cost_info */,
"table": {
"table_name": "t2",
"access_type": "ALL",
"rows_examined_per_scan": 10,
"rows_produced_per_join": 1,
"filtered": "10.00",
"cost_info": {
"read_cost": "2.02",
"eval_cost": "0.20",
"prefix_cost": "4.02",
"data_read_per_join": "16"
} /* cost_info */,
"used_columns": [
"i",
"j"
] /* used_columns */,
"attached_condition": "(`test`.`t2`.`i` = `test`.`t1`.`i`)"
} /* table */
} /* query_block */
}
] /* group_by_subqueries */
} /* grouping_operation */
} /* query_block */
}
Warnings:
Note 1276 Field or reference 'test.t1.i' of SELECT #2 was resolved in SELECT #1
Note 1003 /* select#1 */ select `test`.`t1`.`i` AS `i` from `test`.`t1` group by (/* select#2 */ select `test`.`t2`.`j` from `test`.`t2` where (`test`.`t2`.`i` = `test`.`t1`.`i`))
DROP TABLE t1, t2;
CREATE TABLE t1 (a INT NOT NULL, b INT NOT NULL, KEY k1 (a, b));
INSERT INTO t1 VALUES (10,1),(10,2),(10,3),(20,4),(20,5),(20,6),
(30,7),(30,8),(30,9),(40,10),(40,11),(40,12),(40,13),
(40,14),(40,15),(40,16),(40,17),(40,18),(40,19),(40,20);
EXPLAIN FORMAT=JSON SELECT a, MIN(b) AS b FROM t1 GROUP BY a ORDER BY b;
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "6.50"
} /* cost_info */,
"ordering_operation": {
"using_temporary_table": true,
"using_filesort": true,
"grouping_operation": {
"using_filesort": false,
"table": {
"table_name": "t1",
"access_type": "range",
"possible_keys": [
"k1"
] /* possible_keys */,
"key": "k1",
"used_key_parts": [
"a"
] /* used_key_parts */,
"key_length": "4",
"rows_examined_per_scan": 11,
"rows_produced_per_join": 11,
"filtered": "100.00",
"using_index_for_group_by": true,
"cost_info": {
"read_cost": "4.30",
"eval_cost": "2.20",
"prefix_cost": "6.50",
"data_read_per_join": "176"
} /* cost_info */,
"used_columns": [
"a",
"b"
] /* used_columns */
} /* table */
} /* grouping_operation */
} /* ordering_operation */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select `test`.`t1`.`a` AS `a`,min(`test`.`t1`.`b`) AS `b` from `test`.`t1` group by `test`.`t1`.`a` order by `b`
DROP TABLE t1;
#
CREATE TABLE t1 (a INT NOT NULL, b CHAR(3) NOT NULL, PRIMARY KEY (a));
INSERT INTO t1 VALUES (1,'ABC'), (2,'EFG'), (3,'HIJ');
CREATE TABLE t2 (a INT NOT NULL,b CHAR(3) NOT NULL,PRIMARY KEY (a, b));
INSERT INTO t2 VALUES (1,'a'),(1,'b'),(3,'F');
EXPLAIN FORMAT=JSON SELECT t1.a, GROUP_CONCAT(t2.b) AS b FROM t1 LEFT JOIN t2 ON t1.a=t2.a GROUP BY t1.a ORDER BY t1.b;
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "6.20"
} /* cost_info */,
"ordering_operation": {
"using_temporary_table": true,
"using_filesort": true,
"grouping_operation": {
"using_filesort": true,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"possible_keys": [
"PRIMARY"
] /* possible_keys */,
"rows_examined_per_scan": 3,
"rows_produced_per_join": 3,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "0.60",
"prefix_cost": "2.61",
"data_read_per_join": "48"
} /* cost_info */,
"used_columns": [
"a",
"b"
] /* used_columns */
} /* table */
},
{
"table": {
"table_name": "t2",
"access_type": "ref",
"possible_keys": [
"PRIMARY"
] /* possible_keys */,
"key": "PRIMARY",
"used_key_parts": [
"a"
] /* used_key_parts */,
"key_length": "4",
"ref": [
"test.t1.a"
] /* ref */,
"rows_examined_per_scan": 1,
"rows_produced_per_join": 3,
"filtered": "100.00",
"using_index": true,
"cost_info": {
"read_cost": "3.00",
"eval_cost": "0.60",
"prefix_cost": "6.21",
"data_read_per_join": "48"
} /* cost_info */,
"used_columns": [
"a",
"b"
] /* used_columns */
} /* table */
}
] /* nested_loop */
} /* grouping_operation */
} /* ordering_operation */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select `test`.`t1`.`a` AS `a`,group_concat(`test`.`t2`.`b` separator ',') AS `b` from `test`.`t1` left join `test`.`t2` on((`test`.`t2`.`a` = `test`.`t1`.`a`)) where 1 group by `test`.`t1`.`a` order by `test`.`t1`.`b`
DROP TABLE t1;
DROP TABLE t2;
#
CREATE TABLE t1 (a INT, b INT);
INSERT INTO t1 VALUES
(1,4),
(2,2), (2,2),
(4,1), (4,1), (4,1), (4,1),
(2,1), (2,1);
EXPLAIN FORMAT=JSON SELECT SUM(b) FROM t1 GROUP BY a WITH ROLLUP;
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "12.82"
} /* cost_info */,
"grouping_operation": {
"using_filesort": true,
"cost_info": {
"sort_cost": "9.00"
} /* cost_info */,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 9,
"rows_produced_per_join": 9,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.02",
"eval_cost": "1.80",
"prefix_cost": "3.82",
"data_read_per_join": "144"
} /* cost_info */,
"used_columns": [
"a",
"b"
] /* used_columns */
} /* table */
} /* grouping_operation */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select sum(`test`.`t1`.`b`) AS `SUM(b)` from `test`.`t1` group by `test`.`t1`.`a` with rollup
DROP TABLE t1;
# Composition of DISTINCT, GROUP BY and ORDER BY
CREATE TABLE t1 (a INT, b INT);
INSERT INTO t1 VALUES (1, 1), (1, 2), (2, 1), (2, 2), (3, 1);
EXPLAIN FORMAT=JSON SELECT DISTINCT SUM(b) s FROM t1 GROUP BY a ORDER BY s;
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "3.01"
} /* cost_info */,
"ordering_operation": {
"using_filesort": true,
"duplicates_removal": {
"using_temporary_table": true,
"using_filesort": false,
"grouping_operation": {
"using_temporary_table": true,
"using_filesort": false,
"table": {
"table_name": "t1",
"access_type": "ALL",
"rows_examined_per_scan": 5,
"rows_produced_per_join": 5,
"filtered": "100.00",
"cost_info": {
"read_cost": "2.01",
"eval_cost": "1.00",
"prefix_cost": "3.01",
"data_read_per_join": "80"
} /* cost_info */,
"used_columns": [
"a",
"b"
] /* used_columns */
} /* table */
} /* grouping_operation */
} /* duplicates_removal */
} /* ordering_operation */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select distinct sum(`test`.`t1`.`b`) AS `s` from `test`.`t1` group by `test`.`t1`.`a` order by `s`
FLUSH STATUS;
SELECT DISTINCT SUM(b) s FROM t1 GROUP BY a ORDER BY s;
s
1
3
SHOW SESSION STATUS WHERE (Variable_name LIKE 'Sort_%' OR Variable_name LIKE 'Created_%_tables') AND Value > 0;
Variable_name Value
Created_tmp_tables 1
Sort_rows 2
Sort_scan 1
DROP TABLE t1;
# "buffer_result" node
CREATE TABLE t1 (a INT NOT NULL);
CREATE TABLE t2 (a INT NOT NULL, PRIMARY KEY (a));
INSERT INTO t1 VALUES (1);
INSERT INTO t2 VALUES (1),(2);
EXPLAIN FORMAT=JSON SELECT SQL_BIG_RESULT DISTINCT t1.a FROM t1,t2 ORDER BY t2.a;
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "2.40"
} /* cost_info */,
"ordering_operation": {
"using_filesort": false,
"duplicates_removal": {
"using_temporary_table": true,
"using_filesort": false,
"buffer_result": {
"using_temporary_table": true,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "system",
"rows_examined_per_scan": 1,
"rows_produced_per_join": 1,
"filtered": "100.00",
"cost_info": {
"read_cost": "0.00",
"eval_cost": "0.20",
"prefix_cost": "0.00",
"data_read_per_join": "8"
} /* cost_info */,
"used_columns": [
"a"
] /* used_columns */
} /* table */
},
{
"table": {
"table_name": "t2",
"access_type": "index",
"key": "PRIMARY",
"used_key_parts": [
"a"
] /* used_key_parts */,
"key_length": "4",
"rows_examined_per_scan": 2,
"rows_produced_per_join": 2,
"filtered": "100.00",
"using_index": true,
"distinct": true,
"cost_info": {
"read_cost": "2.00",
"eval_cost": "0.40",
"prefix_cost": "2.40",
"data_read_per_join": "16"
} /* cost_info */,
"used_columns": [
"a"
] /* used_columns */
} /* table */
}
] /* nested_loop */
} /* buffer_result */
} /* duplicates_removal */
} /* ordering_operation */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select distinct sql_big_result '1' AS `a` from `test`.`t2` order by `test`.`t2`.`a`
DROP TABLE t1, t2;
#
CREATE TABLE t1 (a INT NOT NULL, b INT, PRIMARY KEY (a));
CREATE TABLE t2 (a INT NOT NULL, PRIMARY KEY (a));
INSERT INTO t1 VALUES (1,10), (2,20), (3,30), (4,40);
INSERT INTO t2 VALUES (2), (3), (4), (5);
EXPLAIN FORMAT=JSON SELECT * FROM t2 WHERE t2.a IN (SELECT a FROM t1 WHERE t1.b <> 30);
EXPLAIN
{
"query_block": {
"select_id": 1,
"cost_info": {
"query_cost": "6.41"
} /* cost_info */,
"nested_loop": [
{
"table": {
"table_name": "t1",
"access_type": "ALL",
"possible_keys": [
"PRIMARY"
] /* possible_keys */,
"rows_examined_per_scan": 4,
"rows_produced_per_join": 3,
"filtered": "75.00",
"cost_info": {
"read_cost": "2.21",
"eval_cost": "0.60",
"prefix_cost": "2.81",
"data_read_per_join": "48"
} /* cost_info */,
"used_columns": [
"a",
"b"
] /* used_columns */,
"attached_condition": "(`test`.`t1`.`b` <> 30)"
} /* table */
},
{
"table": {
"table_name": "t2",
"access_type": "eq_ref",
"possible_keys": [
"PRIMARY"
] /* possible_keys */,
"key": "PRIMARY",
"used_key_parts": [
"a"
] /* used_key_parts */,
"key_length": "4",
"ref": [
"test.t1.a"
] /* ref */,
"rows_examined_per_scan": 1,
"rows_produced_per_join": 3,
"filtered": "100.00",
"using_index": true,
"cost_info": {
"read_cost": "3.00",
"eval_cost": "0.60",
"prefix_cost": "6.41",
"data_read_per_join": "24"
} /* cost_info */,
"used_columns": [
"a"
] /* used_columns */
} /* table */
}
] /* nested_loop */
} /* query_block */
}
Warnings:
Note 1003 /* select#1 */ select `test`.`t2`.`a` AS `a` from `test`.`t1` join `test`.`t2` where ((`test`.`t2`.`a` = `test`.`t1`.`a`) and (`test`.`t1`.`b` <> 30))
DROP TABLE t1, t2;
set default_storage_engine= @save_storage_engine;
set optimizer_switch=default;