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Re: Transient plans versus the SPI API

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Transient plans versus the SPI API
Date: 2011-08-03 19:33:09
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Lists: pgsql-hackers
On Wed, Aug 3, 2011 at 3:19 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> This seems like a good design.  Now what would be really cool is if
>> you could observe a stream of queries like this:
>> SELECT a, b FROM foo WHERE c = 123
>> SELECT a, b FROM foo WHERE c = 97
>> SELECT a, b FROM foo WHERE c = 236
>> ...and say, hey, I could just make a generic plan and use it every
>> time I see one of these.  It's not too clear to me how you'd make
>> recognition of such queries cheap enough to be practical, but maybe
>> someone will think of a way...
> Hm, you mean reverse-engineering the parameterization of the query?
> Interesting thought, but I really don't see a way to make it practical.
> In any case, it would amount to making up for a bad decision on the
> application side, ie, not transmitting the query in the parameterized
> form that presumably exists somewhere in the application.  I think
> we'd be better served all around by encouraging app developers to rely
> more heavily on parameterized queries ... but first we have to fix the
> performance risks there.

Fair enough.  I have to admit I'm afraid of them right now.

Robert Haas
The Enterprise PostgreSQL Company

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