From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: max_standby_delay considered harmful |
Date: | 2010-05-05 16:18:30 |
Message-ID: | AANLkTilaha4kDiLHoMNXAPh3wixCaJrK10OxY8Hi5qlP@mail.gmail.com |
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On Wed, May 5, 2010 at 9:58 AM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> Tom Lane wrote:
>> Comments?
>
> There's currently three ways to set max_standby_delay:
>
> max_standby_delay = -1 # Query wins
> max_standby_delay = 0 # Recovery wins
> max_standby_delay > X # Query wins until lag > X.
>
> As Tom points out, the 3rd option has all sorts of problems. I very much
> like the behavior that max_standby_delay tries to accomplish, but I have
> to agree that it's not very reliable as it is. I don't like Tom's
> proposal either; the standby can fall behind indefinitely, and queries
> get a varying grace period.
>
> Let's rip out the concept of a delay altogether, and make it a boolean.
> If you really want your query to finish, set it to -1 (using the current
> max_standby_delay nomenclature). If recovery is important to you, set it
> to 0.
Does my proposal (upthread) to limit this by quantity of WAL rather
than time have any legs, or is that impractical and/or otherwise poor?
...Robert
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