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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