| From: | "Ed L(dot)" <pgsql(at)bluepolka(dot)net> |
|---|---|
| To: | Martijn van Oosterhout <kleptog(at)svana(dot)org> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Understanding EXPLAIN ANALYZE output |
| Date: | 2005-02-09 22:38:32 |
| Message-ID: | 200502091538.32870.pgsql@bluepolka.net |
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| Thread: | |
| Lists: | pgsql-general |
On Wednesday February 9 2005 3:13, Martijn van Oosterhout wrote:
>
> In general, the EXPLAIN ANALYZE output follows the planner
> output as close as possible. If you look at the original query
> posted, it showed an Index Scan costing 4.63..4.63 which means
> the index scan is taking (on average) 4.63ms to return 1 row!
> If it displayed as 4000 or something it would be a lot less
> clear what was going on.
>
> Hope this helps,
Both replies help very much, thanks. Regarding 4.63ms to return
a row, I know I/O speeds vary widely depending on conditions and
hardware, but what would you say is a "red flag" value for the
actual time to retrieve a row. I see that for most of the other
times in this example, 0.01ms to 0.10ms is not unusual.
Ed
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