Re: BUG #10675: alter database set tablespace and unlogged table

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Andres Freund <andres(at)2ndquadrant(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, "maxim(dot)boguk" <maxim(dot)boguk(at)gmail(dot)com>, Pg Bugs <pgsql-bugs(at)postgresql(dot)org>
Subject: Re: BUG #10675: alter database set tablespace and unlogged table
Date: 2014-10-16 08:52:58
Message-ID: CA+U5nMLYYyBtkXnHDugMxFnbNRr37H5yLO9qGvEA9aLRto01ug@mail.gmail.com
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On 16 October 2014 05:26, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:

>> I think manual checkpoints should flush everything.
>>
>> This is a valid use case.
>>
>> What other use case is there for a manual checkpoint?
>
> There's people using frequent manual checkpoints to keep performance
> predictable. Unfortunately that actually can improve jitter quite
> measurably.

Hmm, more discussion required there it would seem.

> If we want to change this, fine, but we shouldn't sneak it into the back
> branches, together with a correctness fix

The bug lies in the default behaviour, which we must fix.

I agree backpatching is awkward, though there may also be people who
believe that a CHECKPOINT flushes everything, plus other related bugs
may be lurking.

Seems like we could backpatch this...
CHECKPOINT [ALL (defult) | PERMANENT]

and people who are doing CHECKPOINT PERMANENT for performance reasons
can add the new keyword easy enough, if we highlight it in the release
notes.

--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

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