From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
---|---|
To: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Comment in snapbuild.c file |
Date: | 2017-08-10 14:17:30 |
Message-ID: | 20170810141730.aclru5gk4yczb3dn@alvherre.pgsql |
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Lists: | pgsql-hackers |
Masahiko Sawada wrote:
> Hi all,
>
> In snapbuild.c file, there is a comment as follows.
>
> * NB: Because of that xmax can be lower than xmin, because we only
> * increase xmax when a catalog modifying transaction commits. While odd
> * looking, it's correct and actually more efficient this way since we hit
> * fast paths in tqual.c.
> */
>
> Maybe we can get rid of the second "because" in the first sentence?
I think the whole para needs to be rethought. I propose this:
* NB: We only increase xmax when a catalog-modifying transaction commits
* (see SnapBuildCommitTxn). Because of this, xmax can be lower than xmin,
* which looks odd but is correct and actually more efficient, since we hit
* fast paths in tqual.c.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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