Re: performance penalty between Postgresql 8.3.8 and 8.4.1 - Mailing list pgsql-performance

From Craig Ringer
Subject Re: performance penalty between Postgresql 8.3.8 and 8.4.1
Date
Msg-id 4B1E4294.6020703@postnewspapers.com.au
Whole thread Raw
In response to Re: performance penalty between Postgresql 8.3.8 and 8.4.1  (Thom Brown <thombrown@gmail.com>)
Responses Re: performance penalty between Postgresql 8.3.8 and 8.4.1  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-performance
On 8/12/2009 6:11 PM, Thom Brown wrote:

> Your output shows that the xdf_admin_hierarchy tables between versions
> are drastically different.  8.3.8 only contains 1 row, whereas 8.4.1
> contains 84211 rows.

That's just because one of them is doing a nested loop where it looks up
a single row from xdf_admin_hierarchy via its primary key on each
iteration. The other plan is doing a hash join on a sequential scan over
xdf_admin_hierarchy so it reports all the rows at once.

--
Craig Ringer

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