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From: David G. Johnston <[email protected]>
To: jian he <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: pg_stat_database view column xact_commit description should be more descriptive?
Date: Thu, 2 Jun 2022 23:59:59 -0700
Message-ID: <CAKFQuwZh1a8USr6fHWBXnagXyn1N6EuYXn1t9gtZ1tXgYZkWPw@mail.gmail.com> (raw)
In-Reply-To: <CACJufxFUjNvGXWO7Rq8y5V8YyoMPGnf9Deeyw61Q=wVTqm-SiQ@mail.gmail.com>
References: <CACJufxFUjNvGXWO7Rq8y5V8YyoMPGnf9Deeyw61Q=wVTqm-SiQ@mail.gmail.com>

On Thursday, June 2, 2022, jian he <[email protected]> wrote:

>
> https://www.postgresql.org/docs/current/monitoring-stats.
> html#MONITORING-PG-STAT-DATABASE-VIEW
>
>> xact_commit bigint
>>
>> Number of transactions in this database that have been committed
>>
> In https://www.postgresql.org/docs/current/sql-begin.html
>
> BEGIN initiates a transaction block, that is, all statements after a BEGIN
>> command will be executed in a single transaction until an explicit COMMIT
>> <https://www.postgresql.org/docs/current/sql-commit.html; or ROLLBACK
>> <https://www.postgresql.org/docs/current/sql-rollback.html; is given. By
>> default (without BEGIN), PostgreSQL executes transactions in “autocommit”
>> mode, that is, each statement is executed in its own transaction and a
>> commit is implicitly performed at the end of the statement (if execution
>> was successful, otherwise a rollback is done).
>>
>
> I guess the pg_stat_database view column *xact_commit *refers to
> 'non-autocommit' transactions?
> If so, should we say something like "Number of  autocommit
> transactions...."
>

My guess is that it doesn’t matter if it’s implicit or explicit and thus
the documentation is correct and adequate.  It does seem easy enough to
prove one way or the other if you think it might be incorrect and thus to
warrant a change to the docs.   If it does vary I’d have reason to suspect
that a pure select query would exhibit different behavior than an insert or
delete query - i.e., whether a new xid is issued makes a difference.

I may experiment myself when I’m back at a computer but as you are raising
the potential issue the research seems like something that should be done
to support the suggestion.  It isn’t like this will require source code
reading to discern.

David J.

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