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From:Øystein Grøvlen Date:December 11 2010 8:21am
Subject:Re: bzr commit into mysql-trunk-bugfixing branch (tor.didriksen:3258)
Bug#58782
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Thanks Tor,   Looks good.  Approved.
See below for one question:

On 12/10/2010 04:00 PM, Tor Didriksen wrote:
> #At file:///export/home/didrik/repo/next-mr-opt-team-wl1393-merge/ based on
> revid:tor.didriksen@stripped
>
>   3258 Tor Didriksen	2010-12-10
>        Bug #58782 Missing rows with SELECT .. WHERE .. IN subquery with full GROUP BY
> and no aggr
>
>        The missing results were caused by a 'group by' which was transformed to an
> 'order by'.
>       @ mysql-test/r/explain.result
>          New explain result, the group by can be eliminated.
>       @ mysql-test/r/group_by.result
>          New test case.
>       @ mysql-test/r/myisam_mrr.result
>          New explain result, the group by can be eliminated.
>       @ mysql-test/r/myisam_mrr_cost.result
>          New explain result, the group by can be eliminated.
>       @ mysql-test/r/myisam_mrr_cost_icp.result
>          New explain result, the group by can be eliminated.
>       @ mysql-test/r/myisam_mrr_icp.result
>          New explain result, the group by can be eliminated.
>       @ mysql-test/r/myisam_mrr_none.result
>          New explain result, the group by can be eliminated.
>       @ mysql-test/r/order_by_icp_mrr.result
>          New (correct) result.
>       @ mysql-test/r/order_by_none.result
>          New (correct) result.
>       @ mysql-test/t/group_by.test
>          New test case.
>       @ sql/sql_select.cc
>          If the query as a GROUP BY, which can be converted to an ORDER BY,
>          we can eliminate it for subqueries.

...

> === modified file 'mysql-test/r/myisam_mrr_cost_icp.result'
> --- a/mysql-test/r/myisam_mrr_cost_icp.result	2010-12-06 13:10:10 +0000
> +++ b/mysql-test/r/myisam_mrr_cost_icp.result	2010-12-10 15:00:25 +0000
> @@ -347,7 +347,7 @@ GROUP BY t2.pk
>   );
>   id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
>   1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
> -2	SUBQUERY	t2	ref	int_key	int_key	5	const	1	100.00	Using index condition; Using
> where; Using filesort
> +2	SUBQUERY	t2	ref	int_key	int_key	5	const	1	100.00	Using index condition
>   Warnings:
>   Note	1003	select min(`test`.`t1`.`pk`) AS `MIN(t1.pk)` from `test`.`t1` where 0
>   DROP TABLE t1, t2;

For this query, if I replace GROUP BY with ORDER BY, "Using filesort" is 
still there.  Is that a reason for concern?

--
Øystein


Thread
bzr commit into mysql-trunk-bugfixing branch (tor.didriksen:3258) Bug#58782Tor Didriksen10 Dec
  • Re: bzr commit into mysql-trunk-bugfixing branch (tor.didriksen:3258)Bug#58782Jorgen Loland10 Dec
  • Re: bzr commit into mysql-trunk-bugfixing branch (tor.didriksen:3258)Bug#58782Øystein Grøvlen11 Dec
    • Re: bzr commit into mysql-trunk-bugfixing branch (tor.didriksen:3258)Bug#58782Jorgen Loland13 Dec