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MDEV-32294 fix_fields() problem with inconsistent outer context paths
As part of optimization, we can simplify queries by merging a derived table into it's parent instead of materializing it. When this happens the context paths, describing how each SELECT_LEX is positioned in our query needs updating. The best place to do this is in the call to SELECT_LEX::exclude_level(). We follow MySQLs example here. Approved by Sanja Byelkin (sanja@mariadb.com)
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‎mysql-test/main/subquery_merge.result‎

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#
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# MDEV-32294 2nd execution problem with inconsistent outer context paths
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#
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SELECT
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(
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WITH x AS
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(
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WITH RECURSIVE x ( x ) AS
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(
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SELECT 1 UNION SELECT x FROM x
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)
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SELECT * FROM x WHERE x IN
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(
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SELECT x FROM x WHERE
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(
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SELECT 1 GROUP BY x HAVING ( x )
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)
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)
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)
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SELECT * FROM x
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) AS R;
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R
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1
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SELECT * FROM (
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WITH RECURSIVE x ( a ) AS ( SELECT 1 UNION SELECT a FROM x )
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SELECT * FROM x
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WHERE a IN (
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SELECT a FROM x WHERE ( SELECT 1 GROUP BY a HAVING ( a ) )
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)
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) as dt ;
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a
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1
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create table t1 (a int) engine=myisam;
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insert into t1 values (1), (2);
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create table t2 (b int) engine=myisam;
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insert into t2 values (3), (1);
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create table t3 (c int) select a as c from t1;
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select * from
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(
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with recursive x as ( select a from t1 union select a+1 from x where a < 4 )
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select * from x where a in
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(
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select a from x where
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(
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select b from t2 where b < 3 group by a having a > 0
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) <> 0
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)
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) dt;
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a
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1
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2
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3
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4
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select * from
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(
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with x as ( select distinct a from t1 )
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select * from x where a in
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(
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select a from x where
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(
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select b from t2 where b < 3 group by a having a > 0
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) <> 0
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)
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) dt;
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a
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1
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2
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select * from
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(
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select * from t1 where a in
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(
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select a from t1 where
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(
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select b from t2 where b < 3 group by a having a > 0
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) <> 0
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)
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) dt;
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a
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1
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2
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select * from
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(
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select * from t1 where a in
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(
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select a from t1 where
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(
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select b from t2 where b < 3 group by a
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) <> 0
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)
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) dt;
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a
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1
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2
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select * from
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(
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select * from t3 where c in
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(
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select a from t1 where
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(
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select b from t2 where b < 3 group by a
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) <> 0
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)
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) dt;
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c
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1
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2
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select * from
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(
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select * from t3 where c in
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(
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select a from t1 where
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(
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select b from t2 where a > 0 and b < 3
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) <> 0
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)
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) dt;
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c
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1
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2
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select * from
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(
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select * from t3 where c in
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(
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select a from t1 where
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(
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select b from t2 where a > 0 and b < 3
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) <> 0
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)
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) dt
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where dt.c > 1;
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c
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2
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select * from
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(
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select * from t3 where c in
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(
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select a from t1 where
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(
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select b from t2
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where a > 0 and b < 3
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) <> 0
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)
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) dt;
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c
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1
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2
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prepare stmt from "with cte as
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( select * from t3 where c in
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(
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select a from t1 where
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(
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select b from t2 where a > 0 and b < 3
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) <> 0
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)
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)
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select * from cte";
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execute stmt;
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c
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1
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2
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execute stmt;
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c
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1
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2
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deallocate prepare stmt;
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drop table t1, t2, t3;
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#
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# End of 10.11 tests
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#

‎mysql-test/main/subquery_merge.test‎

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--echo #
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--echo # MDEV-32294 2nd execution problem with inconsistent outer context paths
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--echo #
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SELECT
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(
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WITH x AS
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(
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WITH RECURSIVE x ( x ) AS
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(
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SELECT 1 UNION SELECT x FROM x
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)
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SELECT * FROM x WHERE x IN
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(
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SELECT x FROM x WHERE
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(
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SELECT 1 GROUP BY x HAVING ( x )
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)
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)
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)
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SELECT * FROM x
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) AS R;
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SELECT * FROM (
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WITH RECURSIVE x ( a ) AS ( SELECT 1 UNION SELECT a FROM x )
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SELECT * FROM x
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WHERE a IN (
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SELECT a FROM x WHERE ( SELECT 1 GROUP BY a HAVING ( a ) )
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)
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) as dt ;
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create table t1 (a int) engine=myisam;
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insert into t1 values (1), (2);
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create table t2 (b int) engine=myisam;
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insert into t2 values (3), (1);
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create table t3 (c int) select a as c from t1;
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select * from
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(
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with recursive x as ( select a from t1 union select a+1 from x where a < 4 )
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select * from x where a in
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(
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select a from x where
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(
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select b from t2 where b < 3 group by a having a > 0
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) <> 0
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)
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) dt;
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select * from
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(
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with x as ( select distinct a from t1 )
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select * from x where a in
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(
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select a from x where
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(
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select b from t2 where b < 3 group by a having a > 0
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) <> 0
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)
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) dt;
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select * from
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(
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select * from t1 where a in
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(
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select a from t1 where
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(
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select b from t2 where b < 3 group by a having a > 0
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) <> 0
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)
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) dt;
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select * from
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(
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select * from t1 where a in
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(
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select a from t1 where
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(
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select b from t2 where b < 3 group by a
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) <> 0
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)
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) dt;
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select * from
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(
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select * from t3 where c in
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(
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select a from t1 where
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(
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select b from t2 where b < 3 group by a
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) <> 0
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)
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) dt;
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select * from
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(
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select * from t3 where c in
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(
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select a from t1 where
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(
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select b from t2 where a > 0 and b < 3
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) <> 0
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)
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) dt;
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select * from
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(
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select * from t3 where c in
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(
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select a from t1 where
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(
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select b from t2 where a > 0 and b < 3
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) <> 0
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)
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) dt
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where dt.c > 1;
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select * from
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(
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select * from t3 where c in
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(
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select a from t1 where
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(
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select b from t2
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where a > 0 and b < 3
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) <> 0
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)
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) dt;
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let $q=
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with cte as
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( select * from t3 where c in
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(
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select a from t1 where
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(
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select b from t2 where a > 0 and b < 3
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) <> 0
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)
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)
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select * from cte;
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eval prepare stmt from "$q";
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execute stmt;
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execute stmt;
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deallocate prepare stmt;
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drop table t1, t2, t3;
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--echo #
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--echo # End of 10.11 tests
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--echo #

‎sql/sql_lex.cc‎

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@@ -3348,6 +3348,15 @@ void st_select_lex_unit::exclude_level()
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SELECT_LEX_UNIT **last= 0;
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for (SELECT_LEX_UNIT *u= sl->first_inner_unit(); u; u= u->next_unit())
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{
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for (SELECT_LEX *inner_sel= u->first_select();
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inner_sel; inner_sel= inner_sel->next_select())
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{
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if (&sl->context == inner_sel->context.outer_context)
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inner_sel->context.outer_context = &sl->outer_select()->context;
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}
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if (u->fake_select_lex &&
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u->fake_select_lex->context.outer_context == &sl->context)
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u->fake_select_lex->context.outer_context= &sl->outer_select()->context;
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u->master= master;
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last= (SELECT_LEX_UNIT**)&(u->next);
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}

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