Re: WAL Bypass for indexes - Mailing list pgsql-hackers

From Jonah H. Harris
Subject Re: WAL Bypass for indexes
Date
Msg-id 36e682920604021800r9a22afaob87f09ae4e2037a9@mail.gmail.com
Whole thread Raw
In response to Re: WAL Bypass for indexes  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: WAL Bypass for indexes  (Tom Lane <tgl@sss.pgh.pa.us>)
Re: WAL Bypass for indexes  (Mark Dilger <pgsql@markdilger.com>)
List pgsql-hackers
> AFAICS there are no circumstances, ever, in which update-in-place is
> "safe".  (No transaction can guarantee that it will commit.)

In our case, it is totally safe.  I'd certainly like to discuss it
with you sometime at the anniversary.

> Martin's proposal at least looks sensible; he just hasn't quite made the
> case that it's worth doing ... I agree that it likely would never be the
> default. But it could be a good tradeoff for some cases.

I guess I can think of a few instances, but none that I would've
chosen to use it in.  IIRC, it's also more likely to increase the cost
of checkpointing and/or require a good amount of bgwriter tuning.

As long as it's optional, I guess it's OK to let the administrator
deal with recovery.  Of course, in addition to no-fsync, we'll have
another *possibly* dangerous option.  BTW, I've seen no-fsync used far
too many times because people think they're hardware is invincible.

My only suggestion is to make sure it's a very well documented option.

--
Jonah H. Harris, Database Internals Architect
EnterpriseDB Corporation
732.331.1324


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