>Zitat von azurIt <azurit AT pobox DOT sk>:
>
>> Hi,
>>
>> i'm having some MySQL performance difficulties so i started to  
>> search what can i do better. My table 'File' had these indexes  
>> created:
>> CREATE INDEX file_jobid_idx on File (JobId);
>> CREATE INDEX file_jpf_idx on File (JobId, PathId, FilenameId);
>>
>> Which looks correct according to documentation:
>> http://www.bacula.org/en/dev-manual/main/main/Catalog_Maintenance.html
>>
>> BUT! The first index apperas to be unneeded as it's part of the  
>> second index. According to MySQL documentation, 'any leftmost prefix  
>> of the index can be used by the optimizer to find row':
>> http://dev.mysql.com/doc/refman/5.5/en/multiple-column-indexes.html
>>
>> I suggest to remove it.
>>
>> azur
>
>Would also apply to PostgreSQL i guess:
>http://www.postgresql.org/docs/9.2/interactive/indexes-multicolumn.html
>
>Any comment why the additional single column index could be useful?


No statement from developers regarding this?

azur

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