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|
SELECT table_name, column_name FROM information_schema.columns where table_name="OPTIMIZER_TRACE";
table_name column_name
OPTIMIZER_TRACE QUERY
OPTIMIZER_TRACE TRACE
OPTIMIZER_TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE
OPTIMIZER_TRACE INSUFFICIENT_PRIVILEGES
show variables like 'optimizer_trace';
Variable_name Value
optimizer_trace enabled=off,one_line=off
set optimizer_trace="enabled=on,one_line=on";
show variables like 'optimizer_trace';
Variable_name Value
optimizer_trace enabled=on,one_line=on
set optimizer_trace="enabled=off,one_line=off";
create table t1 (a int, b int);
insert into t1 values (1,2),(2,3);
create table t2 (b int);
insert into t2 values (1),(2);
create function f1 (a int) returns INT
return 1;
create view v1 as select * from t1 where t1.a=1;
create view v2 as select * from t1 where t1.a=1 group by t1.b;
set optimizer_trace="enabled=on,one_line=off";
# Mergeable views/derived tables
select * from v1;
a b
1 2
select * from information_schema.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
select * from v1 {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"join_preparation": {
"select_id": 2,
"steps": [
{
"expanded_query": "/* select#2 */ select `t1`.`a` AS `a`,`t1`.`b` AS `b` from `t1` where `t1`.`a` = 1"
}
]
}
},
{
"expanded_query": "/* select#1 */ select `t1`.`a` AS `a`,`t1`.`b` AS `b` from `v1`"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"view": {
"table": "v1",
"select_id": 2,
"merged": true
}
},
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "t1.a = 1",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "multiple equal(1, t1.a)"
},
{
"transformation": "constant_propagation",
"resulting_condition": "multiple equal(1, t1.a)"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "multiple equal(1, t1.a)"
}
]
}
},
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": []
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
select * from (select * from t1)q;
a b
1 2
2 3
select * from information_schema.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
select * from (select * from t1)q {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"join_preparation": {
"select_id": 2,
"steps": [
{
"expanded_query": "/* select#2 */ select `t1`.`a` AS `a`,`t1`.`b` AS `b` from `t1`"
}
]
}
},
{
"expanded_query": "/* select#1 */ select `t1`.`a` AS `a`,`t1`.`b` AS `b` from (/* select#2 */ select `t1`.`a` AS `a`,`t1`.`b` AS `b` from `t1`) `q`"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"derived": {
"table": "q",
"select_id": 2,
"merged": true
}
},
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
# Non-Mergeable views
select * from v2;
a b
1 2
select * from information_schema.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
select * from v2 {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"join_preparation": {
"select_id": 2,
"steps": [
{
"expanded_query": "/* select#2 */ select `t1`.`a` AS `a`,`t1`.`b` AS `b` from `t1` where `t1`.`a` = 1 group by `t1`.`b`"
}
]
}
},
{
"expanded_query": "/* select#1 */ select `v2`.`a` AS `a`,`v2`.`b` AS `b` from `v2`"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"view": {
"table": "v2",
"select_id": 2,
"merged": false
}
},
{
"join_optimization": {
"select_id": 2,
"steps": [
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "t1.a = 1",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "multiple equal(1, t1.a)"
},
{
"transformation": "constant_propagation",
"resulting_condition": "multiple equal(1, t1.a)"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "multiple equal(1, t1.a)"
}
]
}
},
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": []
}
]
}
},
{
"table_dependencies": [
{
"table": "v2",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
}
]
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": [
{
"join_execution": {
"select_id": 2,
"steps": []
}
}
]
}
}
]
} 0 0
drop table t1,t2;
drop view v1,v2;
drop function f1;
#
# ref-keyues test
#
create table t0 (a int);
INSERT INTO t0 VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t1 (a int, b int, c int, key(a));
insert into t1 select A.a*10 + B.a, A.a*10 + B.a, A.a*10 + B.a from t0 A, t0 B;
create table t2(a int, b int, c int , key(a));
insert into t2 select A.a*10 + B.a, A.a*10 + B.a, A.a*10 + B.a from t0 A, t0 B;
explain select * from t1,t2 where t1.a=t2.b+2 and t2.a= t1.b;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL a NULL NULL NULL 100 Using where
1 SIMPLE t2 ref a a 5 test.t1.b 1 Using where
select * from information_schema.OPTIMIZER_TRACE;
QUERY TRACE MISSING_BYTES_BEYOND_MAX_MEM_SIZE INSUFFICIENT_PRIVILEGES
explain select * from t1,t2 where t1.a=t2.b+2 and t2.a= t1.b {
"steps": [
{
"join_preparation": {
"select_id": 1,
"steps": [
{
"expanded_query": "select `t1`.`a` AS `a`,`t1`.`b` AS `b`,`t1`.`c` AS `c`,`t2`.`a` AS `a`,`t2`.`b` AS `b`,`t2`.`c` AS `c` from `t1` join `t2` where `t1`.`a` = `t2`.`b` + 2 and `t2`.`a` = `t1`.`b`"
}
]
}
},
{
"join_optimization": {
"select_id": 1,
"steps": [
{
"condition_processing": {
"condition": "WHERE",
"original_condition": "t1.a = t2.b + 2 and t2.a = t1.b",
"steps": [
{
"transformation": "equality_propagation",
"resulting_condition": "t1.a = t2.b + 2 and multiple equal(t2.a, t1.b)"
},
{
"transformation": "constant_propagation",
"resulting_condition": "t1.a = t2.b + 2 and multiple equal(t2.a, t1.b)"
},
{
"transformation": "trivial_condition_removal",
"resulting_condition": "t1.a = t2.b + 2 and multiple equal(t2.a, t1.b)"
}
]
}
},
{
"table_dependencies": [
{
"table": "t1",
"row_may_be_null": false,
"map_bit": 0,
"depends_on_map_bits": []
},
{
"table": "t2",
"row_may_be_null": false,
"map_bit": 1,
"depends_on_map_bits": []
}
]
},
{
"ref_optimizer_key_uses": [
{
"table": "t1",
"field": "a",
"equals": "t2.b + 2",
"null_rejecting": false
},
{
"table": "t2",
"field": "a",
"equals": "t1.b",
"null_rejecting": true
}
]
}
]
}
},
{
"join_execution": {
"select_id": 1,
"steps": []
}
}
]
} 0 0
drop table t1,t2,t0;
|
