Re: join over 12 tables takes 3 secs to plan - Mailing list pgsql-performance

From Neil Conway
Subject Re: join over 12 tables takes 3 secs to plan
Date
Msg-id 1477.24.112.166.30.1041542488.squirrel@mailbox.samurai.com
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In response to Re: join over 12 tables takes 3 secs to plan  (Hilmar Lapp <hlapp@gmx.net>)
Responses Re: join over 12 tables takes 3 secs to plan  (Hilmar Lapp <hlapp@gmx.net>)
List pgsql-performance
Hilmar Lapp said:
> As an added note, appreciating that query optimization is a difficult
> problem, and I do think PostgreSQL is a great product. Having said
> that, I've written 16-table joins for Oracle and always found them to
> plan within a second or two, so that's why I thought there's nothing
> special about the query I posted ... I'm not saying this to be bashful
> about PostgreSQL, but rather to suggest that apparently there are ways
> to do it pretty fast.

I'm sure there is room for improvement -- either by adding additional
heuristics to the default optimizer, by improving GEQO, or by implementing
another method for non-exhaustive search for large join queries (there are
several ways to handle large join queries, only one of which uses a
genetic algorithm: see "Query Optimization" (Ioannidis, 1996) for a good
introductory survey).

If you'd like to take a shot at improving it, let me know if I can be of
any assistance :-)

Cheers,

Neil



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