| From: | Peter Geoghegan <pg(at)heroku(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | 山田聡 <satoshi(dot)yamada(dot)pg(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Why standby.max_connections must be higher than primary.max_connections? |
| Date: | 2013-12-11 23:00:58 |
| Message-ID: | CAM3SWZT_y1BY+45Jg1A7xdY=jbsixN8kPhpG7Sc0puYhCGt83w@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Dec 10, 2013 at 1:17 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> Because the KnownAssignedXIDs and lock tables on the standby need to
> be large enough to contain the largest snapshot and greatest number of
> AccessExclusiveLocks that could exist on the master at any given time.
Right. Initially during the development of Hot Standby, it looked like
the "max_connections >= master's" requirement on standbys wasn't going
to be necessary, or could be avoided. However, Simon gave up on that
idea on pragmatic grounds here:
http://www.postgresql.org/message-id/1252002165.2889.467.camel@ebony.2ndQuadrant
I'd thought about revisiting this myself, but I think that the impetus
to do so is lessened by recent work on logical replication.
--
Peter Geoghegan
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