Type:
Bug
Priority:
Major
Resolution:
Fixed
Affects Version/s:
None
Fix Version/s:
None
Component/s:
None
The following query
SELECT
a AS field1,
alias2.d AS field2,
alias2.f AS field3,
alias2.e AS field4,
b AS field5
FROM t1, t2 AS alias2, t2 AS alias3
WHERE alias3.c IN ( SELECT 9 UNION SELECT 4 )
GROUP BY field1, field2, field3, field4, field5
LIMIT_ROWS_EXAMINED 50338;
on the test data finishes with the warning " 1930 Query execution was interrupted. The query examined at least 50339 rows...". According to the session status, it examines over 1.2 million rows:
Handler_read_key 449
Handler_read_rnd 4990
Handler_read_rnd_next 426055
Handler_tmp_write 840053
Handler_write 4
EXPLAIN:
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 10 100.00 Using temporary; Using filesort
1 PRIMARY alias2 ALL NULL NULL NULL NULL 500 100.00 Using join buffer (flat, BNL join)
1 PRIMARY alias3 index NULL c 5 NULL 500 100.00 Using where; Using index; Using join buffer (incremental, BNL join)
2 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL NULL No tables used
3 DEPENDENT UNION NULL NULL NULL NULL NULL NULL NULL NULL No tables used
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL NULL
Warnings:
Note 1003 select `test`.`t1`.`a` AS `field1`,`test`.`alias2`.`d` AS `field2`,`test`.`alias2`.`f` AS `field3`,`test`.`alias2`.`e` AS `field4`,`test`.`t1`.`b` AS `field5` from `test`.`t1` join `test`.`t2` `alias2` join `test`.`t2` `alias3` where <expr_cache><`test`.`alias3`.`c`>(<in_optimizer>(`test`.`alias3`.`c`,<exists>(select 9 having (<cache>(`test`.`alias3`.`c`) = <ref_null_helper>(9)) union select 4 having (<cache>(`test`.`alias3`.`c`) = <ref_null_helper>(4))))) group by `test`.`t1`.`a`,`test`.`alias2`.`d`,`test`.`alias2`.`f`,`test`.`alias2`.`e`,`test`.`t1`.`b`
Optimizer_switch (default):
index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,index_condition_pushdown=on,derived_merge=on,derived_with_keys=on,firstmatch=on,loosescan=on,materialization=on,in_to_exists=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr=off,mrr_cost_based=off,mrr_sort_keys=off,outer_join_with_cache=on,semijoin_with_cache=on,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=off,table_elimination=on
bzr version-info
revision-id: timour@askmonty.org-20120213145248-tlvsd794o83odf2r
date: 2012-02-13 16:52:48 +0200
build-date: 2012-02-15 03:34:36 +0400
revno: 3417
Test case is attached.
relates to
MDEV-28
LIMIT ROWS EXAMINED clause to limit the number of rows examined during SELECT processing
Closed
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