mirror of
https://github.com/MariaDB/server.git
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e987b9350c
(Review input addressed)
(Added handling of UPDATE/DELETE and partitioning w/o index)
If the properties of the used collation allow, do the following
equivalent rewrites:
1. UPPER(key_col)=expr -> key_col=expr
expr=UPPER(key_col) -> expr=key_col
(also rewrite both sides of the equality at the same time)
2. UPPER(key_col) IN (constant-list) -> key_col IN (constant-list)
- Mark utf8mb{3,4}_general_ci as collations that allow this.
- Add optimizer_switch='sargable_casefold=ON' to control this.
(ON by default in this patch)
- Cover the rewrite in Optimizer Trace, rewrite name is
"sargable_casefold_removal".
278 lines
10 KiB
Text
278 lines
10 KiB
Text
set
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@tmp_switch_sarg_casefold=@@optimizer_switch,
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optimizer_switch='sargable_casefold=on';
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create table t1 (
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col1 varchar(32),
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col2 varchar(32),
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col3 char(32),
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col4 text,
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key(col1),
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key(col2),
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key(col3),
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key(col4(32))
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) collate utf8mb3_general_ci;
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insert into t1
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select
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concat('A-', seq),
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concat('A-', seq),
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concat('A-', seq),
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concat('A-', seq)
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from seq_1_to_100;
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analyze table t1 persistent for all;
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Table Op Msg_type Msg_text
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test.t1 analyze status Engine-independent statistics collected
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test.t1 analyze Warning Engine-independent statistics are not collected for column 'col4'
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test.t1 analyze status Table is already up to date
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# Basic examples. All should use ref(col1):
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explain
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select * from t1 where upper(col1)='A-3';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref col1 col1 99 const 1 Using index condition
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select * from t1 where upper(col1)='A-3';
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col1 col2 col3 col4
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A-3 A-3 A-3 A-3
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explain
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select * from t1 where ucase(col1)='a-3';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref col1 col1 99 const 1 Using index condition
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select * from t1 where ucase(col1)='a-3';
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col1 col2 col3 col4
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A-3 A-3 A-3 A-3
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explain select * from t1 where 'abc'=upper(col1);
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref col1 col1 99 const 1 Using index condition
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explain select * from t1 where 'xyz'=ucase(col1);
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref col1 col1 99 const 1 Using index condition
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create view v1 as select * from t1;
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explain select * from v1 where 'abc'=upper(col1);
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref col1 col1 99 const 1 Using index condition
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drop view v1;
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explain select * from t1 where upper(col3)='a-3';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref col3 col3 97 const 1 Using index condition
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explain select * from t1 where upper(col4)='a-3';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref col4 col4 99 const 1 Using where
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# must not be rewritten:
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explain select * from t1 where ucase(col1 collate utf8mb3_bin)='a-3';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 100 Using where
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# Will not do the rewrite due to collation mismatch:
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explain select * from t1 where ucase(col1)=_utf8mb3'abc' COLLATE utf8mb3_bin;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 100 Using where
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drop table t1;
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create table t1 (
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col1 varchar(32),
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col2 varchar(32),
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col3 char(32),
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col4 text,
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key(col1),
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key(col2),
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key(col3),
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key(col4(32))
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) collate utf8mb4_general_ci;
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insert into t1
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select
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concat('A-', seq),
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concat('A-', seq),
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concat('A-', seq),
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concat('A-', seq)
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from seq_1_to_100;
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analyze table t1 persistent for all;
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Table Op Msg_type Msg_text
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test.t1 analyze status Engine-independent statistics collected
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test.t1 analyze Warning Engine-independent statistics are not collected for column 'col4'
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test.t1 analyze status Table is already up to date
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# Basic examples. All should use ref(col1):
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explain
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select * from t1 where upper(col1)='A-3';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref col1 col1 131 const 1 Using index condition
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select * from t1 where upper(col1)='A-3';
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col1 col2 col3 col4
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A-3 A-3 A-3 A-3
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explain
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select * from t1 where ucase(col1)='a-3';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref col1 col1 131 const 1 Using index condition
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select * from t1 where ucase(col1)='a-3';
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col1 col2 col3 col4
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A-3 A-3 A-3 A-3
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explain select * from t1 where 'abc'=upper(col1);
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref col1 col1 131 const 1 Using index condition
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explain select * from t1 where 'xyz'=ucase(col1);
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref col1 col1 131 const 1 Using index condition
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create view v1 as select * from t1;
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explain select * from v1 where 'abc'=upper(col1);
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref col1 col1 131 const 1 Using index condition
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drop view v1;
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explain select * from t1 where upper(col3)='a-3';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref col3 col3 129 const 1 Using index condition
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explain select * from t1 where upper(col4)='a-3';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ref col4 col4 131 const 1 Using where
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# must not be rewritten:
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explain select * from t1 where ucase(col1 collate utf8mb4_bin)='a-3';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 100 Using where
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# Will not do the rewrite due to collation mismatch:
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explain select * from t1 where ucase(col1)=_utf8mb4'abc' COLLATE utf8mb4_bin;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 100 Using where
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#
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# Check if optimizer_switch turns the rewrite off:
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#
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set
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@save_os=@@optimizer_switch,
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optimizer_switch='sargable_casefold=off';
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explain select * from t1 where upper(col1)='A-3';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 100 Using where
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explain select * from t1 where ucase(col1)='a-3';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 100 Using where
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set optimizer_switch=@save_os;
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# The following will not do the rewrite because the comparison
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# is done as DOUBLEs. Come to think of it, it won't harm to do
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# the rewrite but it is outside of the scope of this patch:
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explain select * from t1 where ucase(col1)=123.456;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 100 Using where
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select
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coercibility(upper(col1))
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from t1 limit 1;
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coercibility(upper(col1))
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2
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select coercibility(_utf8mb3'abc' COLLATE utf8mb3_bin);
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coercibility(_utf8mb3'abc' COLLATE utf8mb3_bin)
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0
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# This is transformed too even if it doesn't create any new
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# [potential] access paths:
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explain format=json select * from t1 where upper(col1)=upper(col2);
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EXPLAIN
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{
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"query_block": {
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"select_id": 1,
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"cost": 0.0256761,
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"nested_loop": [
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{
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"table": {
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"table_name": "t1",
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"access_type": "ALL",
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"loops": 1,
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"rows": 100,
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"cost": 0.0256761,
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"filtered": 100,
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"attached_condition": "t1.col2 = t1.col1"
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}
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}
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]
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}
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}
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#
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# Check if ref access works
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#
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create table t2 (
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a varchar(32),
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non_key varchar(32),
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key(a)
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) collate utf8mb4_general_ci;
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insert into t2
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select
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concat('A-', seq),
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concat('A-', seq)
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from seq_1_to_10;
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# Must use ref access for t1:
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explain select * from t1, t2 where upper(t1.col1)= t2.non_key;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 10 Using where
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1 SIMPLE t1 ref col1 col1 131 test.t2.non_key 1
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create table t3 (
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a varchar(32),
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b varchar(32),
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key(a),
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key(b)
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) collate utf8mb3_general_ci;
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insert into t3 values ('abc','ABC'), ('xyz','XYZ');
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explain extended
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select a from t3 ignore index(a) where a=b and upper(b)='ABC';
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id select_type table type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE t3 ref b b 99 const 1 100.00 Using index condition; Using where
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Warnings:
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Note 1003 select `test`.`t3`.`a` AS `a` from `test`.`t3` IGNORE INDEX (`a`) where `test`.`t3`.`a` = `test`.`t3`.`b` and `test`.`t3`.`b` = 'ABC'
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#
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# Check that rewrite isn't applied for non-applicable collations
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#
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create table t4 (
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col1 varchar(32) collate utf8mb3_bin,
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col2 varchar(32) collate utf8mb3_czech_ci,
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col3 varchar(32) collate latin1_bin,
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key(col1),
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key(col2),
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key(col3)
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);
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insert into t4
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select
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concat('A-', seq),
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concat('A-', seq),
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concat('A-', seq)
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from seq_1_to_100;
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analyze table t4 persistent for all;
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Table Op Msg_type Msg_text
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test.t4 analyze status Engine-independent statistics collected
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test.t4 analyze status Table is already up to date
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# None should use ref access:
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explain select * from t4 where upper(col1)='A-3';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t4 ALL NULL NULL NULL NULL 100 Using where
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explain select * from t4 where upper(col2)='a-3';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t4 ALL NULL NULL NULL NULL 100 Using where
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explain select * from t4 where upper(col3)='a-3';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t4 ALL NULL NULL NULL NULL 100 Using where
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#
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# Check that rewrite works for UPPER(col) IN (const-list)
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#
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set
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@tmp_ot= @@optimizer_trace,
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optimizer_trace=1;
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# must use range:
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explain
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select * from t1 where upper(col1) IN ('A-3','A-4','a-5');
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range col1 col1 131 NULL 3 Using index condition
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select * from t1 where upper(col1) IN ('A-3','A-4','a-5');
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col1 col2 col3 col4
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A-3 A-3 A-3 A-3
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A-4 A-4 A-4 A-4
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A-5 A-5 A-5 A-5
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# Will not use the rewrite:
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explain
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select * from t1 where upper(col1) IN ('A-3','A-4',col2);
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 100 Using where
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#
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# MDEV-31946: Optimizer handle UCASE(varchar_col)=... does not work for UPDATE/DELETE
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#
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explain delete from t1 where upper(col1)='A';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range col1 col1 131 NULL 1 Using where
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explain delete from t1 where upper(col1) IN ('A','B');
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range col1 col1 131 NULL 2 Using where
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explain update t1 set col2='ABC' where upper(col1)='A';
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range col1 col1 131 NULL 1 Using where
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explain update t1 set col2='ABC' where upper(col1) IN ('A','B');
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 range col1 col1 131 NULL 2 Using where
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drop table t1,t2,t3,t4;
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set optimizer_switch=@tmp_switch_sarg_casefold;
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