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Constant expressions in WHERE/HAVING/ON clauses aren't cached and evaluated
for each row. This causes slowdown of query execution especially if constant
UDF/SP function are used.
Now WHERE/HAVING/ON expressions are analyzed in the top-bottom direction with
help of the compile function. When analyzer meets a constant item it
sets a flag for the tree transformer to cache the item and doesn't allow tree
walker to go deeper. Thus, the topmost item of a constant expression if
cached. This is done after all other optimizations were applied to
WHERE/HAVING/ON expressions
A helper function called cache_const_exprs is added to the JOIN class.
It calls compile method with caching analyzer and transformer on WHERE,
HAVING, ON expressions if they're present.
The cache_const_expr_analyzer and cache_const_expr_transformer functions are
added to the Item class. The first one check if the item can be cached and
the second caches it if so.
A new Item_cache_datetime class is derived from the Item_cache class.
It caches both int and string values of the underlying item independently to
avoid DATETIME aware int-to-string conversion. Thus it completely relies on
the ability of the underlying item to correctly convert DATETIME value from
int to string and vice versa.
171 lines
3.9 KiB
Text
171 lines
3.9 KiB
Text
drop table if exists t1;
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create table t1 (a varchar(10), key(a));
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insert into t1 values ("a"),("abc"),("abcd"),("hello"),("test");
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explain extended select * from t1 where a like '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 t1 index a a 13 NULL 5 20.00 Using where; Using index
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Warnings:
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Note 1003 select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` like 'abc%')
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explain extended select * from t1 where a like concat('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 t1 index a a 13 NULL 5 20.00 Using where; Using index
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Warnings:
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Note 1003 select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` like <cache>(concat('abc','%')))
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select * from t1 where a like "abc%";
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a
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abc
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abcd
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select * from t1 where a like concat("abc","%");
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a
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abc
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abcd
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select * from t1 where a like "ABC%";
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a
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abc
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abcd
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select * from t1 where a like "test%";
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a
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test
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select * from t1 where a like "te_t";
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a
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test
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select * from t1 where a like "%a%";
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a
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a
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abc
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abcd
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select * from t1 where a like "%abcd%";
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a
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abcd
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select * from t1 where a like "%abc\d%";
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a
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abcd
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drop table t1;
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create table t1 (a varchar(10), key(a));
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insert into t1 values ('a'), ('a\\b');
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select * from t1 where a like 'a\\%' escape '#';
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a
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a\b
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select * from t1 where a like 'a\\%' escape '#' and a like 'a\\\\b';
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a
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a\b
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prepare stmt1 from 'select * from t1 where a like \'a\\%\' escape ?';
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set @esc='#';
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execute stmt1 using @esc;
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a
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a\b
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deallocate prepare stmt1;
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drop table t1;
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create table t1 (a datetime);
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insert into t1 values ('2004-03-11 12:00:21');
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select * from t1 where a like '2004-03-11 12:00:21';
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a
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2004-03-11 12:00:21
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drop table t1;
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SET NAMES koi8r;
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CREATE TABLE t1 (a VARCHAR(10) CHARACTER SET koi8r);
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INSERT INTO t1 VALUES ('ÆÙ×Á'),('æÙ×Á'),('Æù×Á'),('ÆÙ÷Á'),('ÆÙ×á'),('æù÷á');
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INSERT INTO t1 VALUES ('ÆÙ×ÁÐÒÏÌÄÖ'),('æÙ×ÁÐÒÏÌÄÖ'),('Æù×ÁÐÒÏÌÄÖ'),('ÆÙ÷ÁÐÒÏÌÄÖ');
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INSERT INTO t1 VALUES ('ÆÙ×áÐÒÏÌÄÖ'),('ÆÙ×ÁðÒÏÌÄÖ'),('ÆÙ×ÁÐòÏÌÄÖ'),('ÆÙ×ÁÐÒïÌÄÖ');
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INSERT INTO t1 VALUES ('ÆÙ×ÁÐÒÏìÄÖ'),('ÆÙ×ÁÐÒÏÌäÖ'),('ÆÙ×ÁÐÒÏÌÄö'),('æù÷áðòïìäö');
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SELECT * FROM t1 WHERE a LIKE '%Æù×Á%';
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a
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ÆÙ×Á
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æÙ×Á
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Æù×Á
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ÆÙ÷Á
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ÆÙ×á
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æù÷á
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ÆÙ×ÁÐÒÏÌÄÖ
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æÙ×ÁÐÒÏÌÄÖ
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Æù×ÁÐÒÏÌÄÖ
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ÆÙ÷ÁÐÒÏÌÄÖ
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ÆÙ×áÐÒÏÌÄÖ
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ÆÙ×ÁðÒÏÌÄÖ
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ÆÙ×ÁÐòÏÌÄÖ
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ÆÙ×ÁÐÒïÌÄÖ
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ÆÙ×ÁÐÒÏìÄÖ
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ÆÙ×ÁÐÒÏÌäÖ
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ÆÙ×ÁÐÒÏÌÄö
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æù÷áðòïìäö
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SELECT * FROM t1 WHERE a LIKE '%Æù×%';
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a
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ÆÙ×Á
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æÙ×Á
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Æù×Á
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ÆÙ÷Á
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ÆÙ×á
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æù÷á
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ÆÙ×ÁÐÒÏÌÄÖ
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æÙ×ÁÐÒÏÌÄÖ
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Æù×ÁÐÒÏÌÄÖ
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ÆÙ÷ÁÐÒÏÌÄÖ
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ÆÙ×áÐÒÏÌÄÖ
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ÆÙ×ÁðÒÏÌÄÖ
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ÆÙ×ÁÐòÏÌÄÖ
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ÆÙ×ÁÐÒïÌÄÖ
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ÆÙ×ÁÐÒÏìÄÖ
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ÆÙ×ÁÐÒÏÌäÖ
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ÆÙ×ÁÐÒÏÌÄö
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æù÷áðòïìäö
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SELECT * FROM t1 WHERE a LIKE 'Æù×Á%';
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a
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ÆÙ×Á
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æÙ×Á
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Æù×Á
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ÆÙ÷Á
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ÆÙ×á
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æù÷á
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ÆÙ×ÁÐÒÏÌÄÖ
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æÙ×ÁÐÒÏÌÄÖ
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Æù×ÁÐÒÏÌÄÖ
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ÆÙ÷ÁÐÒÏÌÄÖ
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ÆÙ×áÐÒÏÌÄÖ
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ÆÙ×ÁðÒÏÌÄÖ
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ÆÙ×ÁÐòÏÌÄÖ
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ÆÙ×ÁÐÒïÌÄÖ
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ÆÙ×ÁÐÒÏìÄÖ
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ÆÙ×ÁÐÒÏÌäÖ
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ÆÙ×ÁÐÒÏÌÄö
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æù÷áðòïìäö
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DROP TABLE t1;
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SET NAMES cp1250;
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CREATE TABLE t1 (a varchar(250) NOT NULL) DEFAULT CHARACTER SET=cp1250;
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INSERT INTO t1 VALUES
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('Techni Tapes Sp. z o.o.'),
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('Pojazdy Szynowe PESA Bydgoszcz SA Holding'),
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('AKAPESTER 1 P.P.H.U.'),
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('Pojazdy Szynowe PESA Bydgoszcz S A Holding'),
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('PPUH PESKA-I Maria Struniarska');
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select * from t1 where a like '%PESA%';
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a
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Pojazdy Szynowe PESA Bydgoszcz SA Holding
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Pojazdy Szynowe PESA Bydgoszcz S A Holding
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select * from t1 where a like '%PESA %';
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a
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Pojazdy Szynowe PESA Bydgoszcz SA Holding
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Pojazdy Szynowe PESA Bydgoszcz S A Holding
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select * from t1 where a like '%PES%';
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a
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Techni Tapes Sp. z o.o.
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Pojazdy Szynowe PESA Bydgoszcz SA Holding
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AKAPESTER 1 P.P.H.U.
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Pojazdy Szynowe PESA Bydgoszcz S A Holding
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PPUH PESKA-I Maria Struniarska
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select * from t1 where a like '%PESKA%';
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a
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PPUH PESKA-I Maria Struniarska
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select * from t1 where a like '%ESKA%';
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a
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PPUH PESKA-I Maria Struniarska
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DROP TABLE t1;
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select _cp866'aaaaaaaaa' like _cp866'%aaaa%' collate cp866_bin;
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_cp866'aaaaaaaaa' like _cp866'%aaaa%' collate cp866_bin
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1
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set names koi8r;
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select 'andre%' like 'andreÊ%' escape 'Ê';
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'andre%' like 'andreÊ%' escape 'Ê'
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1
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select _cp1251'andre%' like convert('andreÊ%' using cp1251) escape 'Ê';
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_cp1251'andre%' like convert('andreÊ%' using cp1251) escape 'Ê'
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1
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