From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Boosting cost estimates for some built-in functions |
Date: | 2009-10-18 20:45:35 |
Message-ID: | 10334.1255898735@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> On Sun, 2009-10-18 at 14:50 -0400, Tom Lane wrote:
>> I'd like to suggest boosting the built-in cost estimates for the
>> xxx_has_privilege functions to perhaps 10. to_tsquery and to_tsvector
>> maybe should be boosted even higher, but I don't have a good specific
>> number in mind.
> ISTM we should set up a test that measures the cost, of those and other
> functions.
Well, some quick testing suggests that 10x is in the right ballpark for
has_table_privilege versus a simple function such as OID equality,
and that even fairly simple cases of to_tsvector/to_tsquery can be
100x the cost of OID equality. I'm not sure if there is a "typical
case" for the latter given the wide range of possible tsearch
configurations, so trying to benchmark it with any degree of precision
might be pointless.
regards, tom lane
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