Re: increasing the default WAL segment size

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: David Steele <david(at)pgmasters(dot)net>
Cc: Stephen Frost <sfrost(at)snowman(dot)net>, Beena Emerson <memissemerson(at)gmail(dot)com>, tushar <tushar(dot)ahuja(at)enterprisedb(dot)com>, Prabhat Sahu <prabhat(dot)sahu(at)enterprisedb(dot)com>, Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Kuntal Ghosh <kuntalghosh(dot)2007(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: increasing the default WAL segment size
Date: 2017-03-24 19:00:31
Message-ID: CA+Tgmob3xxVZVGoe=_59+=zyZswwS17ax6VgWUxRvZL9BnSJog@mail.gmail.com
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On Wed, Mar 22, 2017 at 6:05 PM, David Steele <david(at)pgmasters(dot)net> wrote:
>> Wait, really? I thought you abandoned this approach because there's
>> then no principled way to handle WAL segments of less than the default
>> size.
>
> I did say that, but I thought I had hit on a compromise.
>
> But, as I originally pointed out the hex characters in the filename are not
> aligned correctly for > 8 bits (< 16MB segments) and using different
> alignments just made it less consistent.

I don't think I understand what the compromise is. Are you saying we
should have one rule for segments < 16MB and another rule for segments
> 16MB? I think using two different rules for file naming depending
on the segment size will be a negative for both tool authors and
ordinary users.

> It would be OK if we were willing to drop the 1,2,4,8 segment sizes because
> then the alignment would make sense and not change the current 16MB
> sequence.

Well, that is true. But the thing I'm trying to do here is to keep
this patch down to what actually needs to be changed in order to
accomplish the original purchase, not squeeze more and more changes
into it.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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