Re: max_standby_delay considered harmful

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@postgresql.org, Bruce Momjian <bruce@momjian.us>, Greg Smith <greg@2ndquadrant.com>, Robert Haas <robertmhaas@gmail.com>, Simon Riggs <simon@2ndquadrant.com>, Josh Berkus <josh@agliodbs.com>
Date: 2010-05-09T00:57:26Z
Lists: pgsql-hackers
Andres Freund <andres@anarazel.de> writes:
> On Sunday 09 May 2010 01:34:18 Bruce Momjian wrote:
>> I think everyone agrees the current code is unusable, per Heikki's
>> comment about a WAL file arriving after a period of no WAL activity, and
>> look how long it took our group to even understand why that fails so
>> badly.

> To be honest its not *that* hard to simply make sure generating wal regularly 
> to combat that. While it surely aint a nice workaround its not much of a 
> problem either.

Well, that's dumping a kluge onto users; but really that isn't the
point.  What we have here is a badly designed and badly implemented
feature, and we need to not ship it like this so as to not
institutionalize a bad design.

I like the proposal of a boolean because it provides only the minimal
feature set of two cases that are both clearly needed and easily
implementable.  Whatever we do later is certain to provide a superset
of those two cases.  If we do something else (and that includes my own
proposal of a straight lock timeout), we'll be implementing something
we might wish to take back later.  Taking out features after they've
been in a release is very hard, even if we realize they're badly
designed.

			regards, tom lane