Re: RES: Degradation of postgres 7.4.5 on FreeBSD/CygWin

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Rodrigo Moreno" <rodrigo(dot)miguel(at)terra(dot)com(dot)br>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: RES: Degradation of postgres 7.4.5 on FreeBSD/CygWin
Date: 2005-02-18 14:59:52
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"Rodrigo Moreno" <rodrigo(dot)miguel(at)terra(dot)com(dot)br> writes:
> max_fsm_pages = 40000
> max_fsm_relations = 2000

> But why after 2 months the database has 1.3gb and after reimport on 900mb ?

40k pages = 320M bytes = 1/3rd of your database. Perhaps you need a
larger setting for max_fsm_pages.

However, 30% bloat of the database doesn't particularly bother me,
especially when you are using infrequent vacuums. Bear in mind that,
for example, the steady-state fill factor of a b-tree index is usually
estimated at less than 70%. A certain amount of wasted space is not
only intended, but essential for reasonable performance.

What you need is to take a more detailed look at the behavior of that
function that's getting so slow. Are the query plans changing? Is
the loop iterating over many more rows than before? You haven't told
us anything that would account for 100x slowdown.

regards, tom lane

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