Re: postgres_fdw: using TABLESAMPLE to collect remote sample

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: postgres_fdw: using TABLESAMPLE to collect remote sample
Date: 2022-02-11 17:39:43
Message-ID: 2080021.1644601183@sss.pgh.pa.us
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Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> writes:
> So here we go. The patch does a very simple thing - it uses TABLESAMPLE
> to collect/transfer just a small sample from the remote node, saving
> both CPU and network.

This is great if the remote end has TABLESAMPLE, but pre-9.5 servers
don't, and postgres_fdw is supposed to still work with old servers.
So you need some conditionality for that.

regards, tom lane

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