Re: Re: [HACKERS] GSoC 2015 proposal: Improve the performance of “ALTER TABLE .. SET LOGGED / UNLOGGED” statement

Andres Freund <andres@anarazel.de> writes:
> On 2015-07-09 10:39:35 -0300, Fabr�zio de Royes Mello wrote:
>> If the "wal_level=minimal" we don't need to force the wal log of the
>> contents. If the "wal_level != minimal" we need just to xlog all the pages,
>> but in both cases we don't need the extra job to create a new datafiles and
>> copy the contents between them. So we'll improve performance, or am I
>> missing something?

> Sure. It'll be a bit faster. I just don't see the peformance increase in
> not that common situations being worth the price we'll pay in
> development, code review, debugging and then maintaining some nontrivial
> code. If this were likely to be a 15 line patch, I'd think differently.

I'm even more worried about the possible reliability problems (ie
introduction of bugs, which are likely to be of the data-eating variety)
that such changes are likely to incur.  So I tend to agree with Andres
that this is probably not a good idea.

            regards, tom lane