Re: disk writes within a transaction

On 02/16/2017 11:33 AM, 2xlp - ListSubscriptions wrote:
> Can someone enlighten me to how postgres handles disk writing? I've read some generic remarks about buffers, but that's about it.
>
> We have a chunk of code that calls Postgres in a less-than-optimal way within a transaction block. I'm wondering where to prioritize fixing it, as the traffic on the wire isn't an issue.
>
> Basically the code looks like this:
>
> begin;
> update foo set foo.a='1' where foo.bar = 1;
> ...
> update foo set foo.b='2' where foo.bar = 1;
> ...
> update foo set foo.c='3' where foo.bar = 1;
> commit;
>
> If the updates are likely to be a memory based operation, consolidating them can wait. If they are likely to hit the disk, I should schedule refactoring this code sooner than later.

I would suggest taking a look at:

https://www.postgresql.org/docs/9.6/static/wal-configuration.html

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com