Bug #38251 Useless external queries should be ignored

Submitted: 21 Jul 2008 0:29 Modified: 21 Jul 2008 13:13
Reporter: Federico Razzoli (OCA) Email Updates:
Status: Verified Impact on me:
None 
Category:MySQL Server: Optimizer Severity:S5 (Performance)
Version:5.0.51 OS:Any
Assigned to: Assigned Account CPU Architecture:Any

[21 Jul 2008 0:29] Federico Razzoli 
Description:
When using a derived table, the external query in some cases may be useless. In my opinion, the optimizer should detect those cases and ignore useless queries. See the examples below.

How to repeat:
EXPLAIN SELECT t.* FROM (SELECT * FROM INFORMATION_SCHEMA.CHARACTER_SETS) AS t

EXPLAIN SELECT t.* FROM (SELECT * FROM INFORMATION_SCHEMA.CHARACTER_SETS ORDER BY 2) AS t ORDER BY 1
[21 Jul 2008 13:13] Valeriy Kravchuk 
Thank you for a reasonable feature request.

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