From: | "Josh Berkus" <josh(at)agliodbs(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-sql(at)postgresql(dot)org |
Subject: | Re: optimizing queries and indexes... |
Date: | 2001-09-16 20:36:38 |
Message-ID: | web-119877@davinci.ethosmedia.com |
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Thread: | |
Lists: | pgsql-sql |
Tom,
> [ Sorry for slow response, I've been out of town ]
Taking a much-deserved vacation, hey? Any new job plans?
> Postgres absolutely does not care: the optimizer will always consider
> both A-join-B and B-join-A orders for every join it has to do. As
> Stephan and Josh noted, you can constrain the join pairs the
> optimizer
> will consider if you use explicit-JOIN syntax --- but each pair will
> be
> considered in both directions.
Fantastic! You may want to point out to unbelievers that MS SQL Server
does not do this; if you fail to put your joins/where clauses in the
*exact* order of the indecies in SQL Server, it ignores them and does a
table scan. This is especially deadly because table scans are about 1/2
as fast in SQL Server as they are in Postgres.
-Josh
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