Re: Bad perf when using DECLARE CURSOR on big table

From: kimaidou <kimaidou(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: postgres performance list <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Bad perf when using DECLARE CURSOR on big table
Date: 2025-03-18 07:48:53
Message-ID: CAMKXKO4OoEaFcfTeZZOx_icTVdUN8a5LKs=VKTpVqQ-jv27Qww@mail.gmail.com
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Indeed, increasing cursor_tuple_fraction TO 0.2 did the trick.
Thanks for the hint Tom !

Le lun. 17 mars 2025 à 16:22, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> a écrit :

> kimaidou <kimaidou(at)gmail(dot)com> writes:
> > I have seen that this DECLARE has bad perf compared to a simple SQL
> query :
>
> > Simple SQL query
> > =====
> > https://explain.dalibo.com/plan/042bc4dc2449adfe
> > 96ms
>
> > DECLARE CURSOR for the same query
> > =====
> > https://explain.dalibo.com/plan/bh83fc0db500a79g#
> > 171 031 ms !!
>
> Raising cursor_tuple_fraction would probably help this case.
>
> regards, tom lane
>

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