>>>-----Messaggio originale-----
>>>Da: Tom Lane [mailto:[EMAIL PROTECTED] 
>>>Inviato: giovedý 13 maggio 2004 17.01
>>>A: Fabio Panizzutti
>>>Cc: 'Shridhar Daithankar'; [EMAIL PROTECTED]
>>>Oggetto: Re: R: [PERFORM] Query plan on identical tables 
>>>differs . Why ? 
>>>
>>>
>>>"Fabio Panizzutti" <[EMAIL PROTECTED]> writes:
>>>> I don't understand why the planner chose a different query plan on 
>>>> identical tables with same indexes .
>>>
>>>Different data statistics; not to mention different table 
>>>sizes (the cost equations are not linear).
>>>
>>>Have you ANALYZEd (or VACUUM ANALYZEd) both tables recently?
>>>
>>>If the stats are up to date but still not doing the right 
>>>thing, you might try increasing the statistics target for 
>>>the larger table's tag_id column.  See ALTER TABLE SET STATISTICS.
>>>
>>>                     regards, tom lane
>>>

All tables are vacumed and analyzed . 
I try so set statistics to 1000 to tag_id columns with ALTER TABLE SET
STATISTIC, revacuum analyze ,  but the planner choose the same query
plan . 
I'm trying now to change the indexes .

Thanks 




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TIP 8: explain analyze is your friend

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