Re: WAL Bypass for indexes

From: "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Martin Scholes" <marty(at)iicolo(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: WAL Bypass for indexes
Date: 2006-04-03 01:00:26
Message-ID: 36e682920604021800r9a22afaob87f09ae4e2037a9@mail.gmail.com
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> 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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