| From: | Matt <msubs(at)philips(dot)org(dot)uk> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | pgsql-bugs(at)postgreSQL(dot)org |
| Subject: | Re: Huge query stalls at PARSE/BIND stage (1) |
| Date: | 2005-11-21 09:01:00 |
| Message-ID: | 1132563660.18269.12.camel@localhost |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-bugs |
> Thanks for the test case. The problem turns out to be sloppy coding in
> exprTypmod(): it recurses twice on the first argument of a COALESCE,
> making for exponential growth in the time needed to process a deep nest
> of COALESCE expressions ... which is exactly what your deeply nested
> FULL JOINs produce for the join USING variables. The patch attached
> fixes it for 8.0.* --- I've committed equivalent fixes as far back as
> 7.4, where the problem originated.
>
> Moral: sometimes an apparently trivial inefficiency isn't so trivial.
Interesting. Thanks Tom. You've saved me an unpleasant workaround.
Glad I could contribute *something*!
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