Re: optimizing queries and indexes...

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От Josh Berkus
Тема Re: optimizing queries and indexes...
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Msg-id web-119877@davinci.ethosmedia.com
обсуждение исходный текст
Ответ на Re: optimizing queries and indexes...  (Tom Lane <tgl@sss.pgh.pa.us>)
Список 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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