Bug #38251 Useless external queries should be ignored
Submitted: 21 Jul 2008 2:29 Modified: 21 Jul 2008 15:13
Reporter: Federico Razzoli
Status: Verified
Category:Server: Optimizer Severity:S5 (Performance)
Version:5.0.51 OS:Any
Assigned to: Evgeny Potemkin Target Version:
Triage: Triaged: D5 (Feature request)

[21 Jul 2008 2:29] 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 15:13] Valeriy Kravchuk 
Thank you for a reasonable feature request.