From: | Gerardo Herzig <gherzig(at)fmed(dot)uba(dot)ar> |
---|---|
To: | pgsql-performance(at)postgresql(dot)org, "pgsql-sql " <pgsql-sql(at)postgresql(dot)org> |
Subject: | performance drop when function argument is evaluated in WHERE clause |
Date: | 2014-04-08 11:53:41 |
Message-ID: | 731037499.293695.1396958021532.JavaMail.root@fmed.uba.ar |
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Lists: | pgsql-performance pgsql-sql |
Hi all. I have a function that uses a "simple" select between 3 tables. There is a function argument to help choose how a WHERE clause applies. This is the code section:
select * from....
[...]
where case $3
when 'I' then [filter 1]
when 'E' then [filter 2]
when 'P' then [filter 3]
else true end
When the function is called with, say, parameter $3 = 'I', the funcion run in 250ms,
but when there is no case involved, and i call directly "with [filter 1]" the function runs in 70ms.
Looks like the CASE is doing something nasty.
Any hints about this?
Thanks!
Gerardo
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