| From: | Kris Jurka <books(at)ejurka(dot)com> |
|---|---|
| To: | Maciek Sakrejda <msakrejda(at)truviso(dot)com> |
| Cc: | Anish Kejariwal <anishkej(at)yahoo(dot)com>, "pgsql-jdbc(at)postgresql(dot)org" <pgsql-jdbc(at)postgresql(dot)org> |
| Subject: | Re: avoid prepared statements on complex queries? |
| Date: | 2011-11-16 21:16:59 |
| Message-ID: | alpine.BSO.2.00.1111161614110.14447@leary.csoft.net |
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| Lists: | pgsql-jdbc |
On Wed, 16 Nov 2011, Maciek Sakrejda wrote:
> Maybe, although I've never seen that happen and as I understand, the
> driver always sends parameters along with the statement when using
> unnamed statements, so I'm not sure what would trigger this.
The standard example is "WHERE col LIKE ?". If the parameter is something
like 'abcdef%' then the query can potentially be converted to a range
scan, but only if knows the parameter value. When preparing this with an
unnamed statement the server has the parameter value, but cannot assume
that the same unnamed statement won't be used with a different parameter
value later and must come up with a plan that is correct for all possible
parameters even if it's not ideal for the current one.
Kris Jurka
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