From: Tom Lane <tgl@sss.pgh.pa.us>
To: Julian Scarfe <julian@avbrief.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Inheritance, unique keys and performance
Date: Sun, 13 Jan 2008 15:47:50 -0500
Message-ID: <8606.1200257270@sss.pgh.pa.us> (raw)
In-Reply-To: <01fb01c8561a$76d6b4a0$0600a8c0@Wilbur>
References: <01a301c85552$24ab6270$0600a8c0@Wilbur>
<21684.1200170118@sss.pgh.pa.us>
<01b601c855c4$8ed20a60$0600a8c0@Wilbur>
<7212.1200250003@sss.pgh.pa.us>
<01fb01c8561a$76d6b4a0$0600a8c0@Wilbur>
"Julian Scarfe" <julian@avbrief.com> writes:
> From: "Tom Lane" <tgl@sss.pgh.pa.us>
>> The
>> problem you've got is that you need a nestloop-with-inner-indexscan
>> plan type, where the inner side is an Append group (that is, an
>> inheritance tree) --- and 8.1 doesn't know how to create such a plan.
>> If you can update to 8.2 or later it should get better.
> Isn't test 3 (scalar subqueries) also a nestloop-with-inner-indexscan with
> an inner Append?
No. The subquery is planned separately and sees the upper query's
variable as a pseudo-constant Param. In neither query does the
planner think that a join is happening.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, julian@avbrief.com
Subject: Re: Inheritance, unique keys and performance
In-Reply-To: <8606.1200257270@sss.pgh.pa.us>
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