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From: Tatsuo Ishii <[email protected]>
To: [email protected]
Cc: [email protected]
Subject: Re: Routing of FDW Queries to Secondary databases
Date: Wed, 22 Apr 2026 14:36:06 +0900 (JST)
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAG9AmsgiQgDhQWZ6viVEWwtX4h_ukjvgN=DhiWKKCAvHMyC=yQ@mail.gmail.com>
References: <CAG9AmsgiQgDhQWZ6viVEWwtX4h_ukjvgN=DhiWKKCAvHMyC=yQ@mail.gmail.com>

> Hi,
> 
> I understand that FDW queries don't get routed to the secondary databases
> since they occur within FETCH blocks.

Yes, currently Pgpool-II does not load balance DECLARE CURSOR/FETCH
(it's documented).  The difficulty is, once DECLARE CURSOR is routed
to particular server, subsequent FETCH must be routed to the server
too. Pgpool-II has to track this.

> Is there any planned work to change
> this.

As far as I know I haven't noticed a request to implement load
balancing for DECLARE CURSOR/FETCH up to now.

> I have one database I'm about to work on clusterizing, but this
> limitation makes pgpool impractical as the read side is only accessed via
> FDWs in all but a very small set of circumstances.
> 
> Again, I realize the existing limitation; I'm just curious if there's any
> work on the horizon to add that capability. If not, I will likely need to
> explore other alternatives for one of the clusters I'm working on.

If there's a strong demand, developers will discuss on implementing
the feature for the next major release of Pgpool-II (planned to be
released by the end of this year).

Regards,
--
Tatsuo Ishii
SRA OSS K.K.
English: http://www.sraoss.co.jp/index_en/
Japanese:http://www.sraoss.co.jp

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