Rod Taylor wrote:
On Fri, 2004-08-20 at 05:37, Gaetano Mendola wrote:
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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.
We can test this.
What are the times without the index, with the index and with the higher
statistics value when using a prepared query?
Using a prepared query:
Without index and default stat 10 : 1.12 ms
Without index and default stat 1000 : 1.25 ms
With index and default stat 10: 1.35 ms
With index and default stat 1000: 1.6 ms
that values are the average obtained after the very first one,
on 20 execution.
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