From: | Gaetano Mendola <mendola(at)bigfoot(dot)com> |
---|---|
To: | Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au> |
Cc: | Richard Huxton <dev(at)archonet(dot)com>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: using an index worst performances |
Date: | 2004-08-20 09:37:27 |
Message-ID: | 4125C657.7000702@bigfoot.com |
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Thread: | |
Lists: | pgsql-performance |
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Christopher Kings-Lynne wrote:
|>>> Without index: 1.140 ms
|>>> With index: 1.400 ms
|>>> With default_statistic_targer = 200: 1.800 ms
|>>
|>>
|>>
|>>
|>> Can I just check that 1.800ms means 1.8 secs (You're using . as the
|>> thousands separator)?
|>>
|>> If it means 1.8ms then frankly the times are too short to mean
|>> anything without running them 100 times and averaging.
|>
|>
|>
|>
|> It mean 1.8 ms and that execution time is sticky to that value even
|> with 1000 times.
|
|
| Given the almost irrelvant difference in the speed of those queries, I'd
| say that with the stats so high, postgres simply takes longer to check
| the statistics to come to the same conclusion. ie. it has to loop over
| 200 rows instead of just 10.
The time increase seems too much.
Regards
Gaetano Mendola
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