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Routing of FDW Queries to Secondary databases
3+ messages / 2 participants
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* Routing of FDW Queries to Secondary databases
@ 2026-04-17 19:11 Adam Blomeke <[email protected]>
  2026-04-22 05:36 ` Re: Routing of FDW Queries to Secondary databases Tatsuo Ishii <[email protected]>
  0 siblings, 1 reply; 3+ messages in thread

From: Adam Blomeke @ 2026-04-17 19:11 UTC (permalink / raw)
  To: [email protected]

Hi,

I understand that FDW queries don't get routed to the secondary databases
since they occur within FETCH blocks. Is there any planned work to change
this. 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.

Cheers,
Adam


^ permalink  raw  reply  [nested|flat] 3+ messages in thread

* Re: Routing of FDW Queries to Secondary databases
  2026-04-17 19:11 Routing of FDW Queries to Secondary databases Adam Blomeke <[email protected]>
@ 2026-04-22 05:36 ` Tatsuo Ishii <[email protected]>
  2026-04-23 17:55   ` Re: Routing of FDW Queries to Secondary databases Adam Blomeke <[email protected]>
  0 siblings, 1 reply; 3+ messages in thread

From: Tatsuo Ishii @ 2026-04-22 05:36 UTC (permalink / raw)
  To: [email protected]; +Cc: [email protected]

> 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





^ permalink  raw  reply  [nested|flat] 3+ messages in thread

* Re: Routing of FDW Queries to Secondary databases
  2026-04-17 19:11 Routing of FDW Queries to Secondary databases Adam Blomeke <[email protected]>
  2026-04-22 05:36 ` Re: Routing of FDW Queries to Secondary databases Tatsuo Ishii <[email protected]>
@ 2026-04-23 17:55   ` Adam Blomeke <[email protected]>
  0 siblings, 0 replies; 3+ messages in thread

From: Adam Blomeke @ 2026-04-23 17:55 UTC (permalink / raw)
  To: Tatsuo Ishii <[email protected]>; +Cc: [email protected]

A lot of our connections operate over foreign data wrappers. We have very
large datasets and we try to segment our analysts off from the actual data
sources. I'd like to be able to balance my read-only FDW queries onto a
secondary database. I've got 2 PGPool instances already, and this would be
beneficial on one of them along with this third one. I realize I'm only one
guy, but having this would be really useful in my implementation.

Cheers,
Adam

On Tue, Apr 21, 2026, 22:36 Tatsuo Ishii <[email protected]> wrote:

> > 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
>


^ permalink  raw  reply  [nested|flat] 3+ messages in thread


end of thread, other threads:[~2026-04-23 17:55 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2026-04-17 19:11 Routing of FDW Queries to Secondary databases Adam Blomeke <[email protected]>
2026-04-22 05:36 ` Tatsuo Ishii <[email protected]>
2026-04-23 17:55   ` Adam Blomeke <[email protected]>

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