From: | "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com> |
---|---|
To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | "Dawid Kuroczko" <qnex42(at)gmail(dot)com>, Perez <arturo(at)ethicist(dot)net>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Cached Query Plans (was: global prepared statements) |
Date: | 2008-04-13 04:21:41 |
Message-ID: | 36e682920804122121y4bf44dbeg53f62fc52316fa81@mail.gmail.com |
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Lists: | pgsql-hackers |
On Sat, Apr 12, 2008 at 10:17 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > Yes, this is worthless on large active databases. The logging
> > overhead alone starts to affect performance.
>
> But somehow, all that stuff with cached plans is free?
Of course not. The first time you execute a query, it is cached... so
you pay the same penalty you do in PG, but in many cases, only once.
In regards to plan re-use, sure there's going to be some contention on
the hash buckets... but that can be mitigated in a lot of ways.
In addition to that, Oracle collects over two thousand other
statistics in real-time... yet somehow Oracle is quite fast. So, I
would say that the usual complaint about collecting stats should be
more an issue of proper implementation than a complaint about the act
of collection itself.
--
Jonah H. Harris, Sr. Software Architect | phone: 732.331.1324
EnterpriseDB Corporation | fax: 732.331.1301
499 Thornall Street, 2nd Floor | jonah(dot)harris(at)enterprisedb(dot)com
Edison, NJ 08837 | http://www.enterprisedb.com/
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