possible small contribution to the PostgreSQL manual? Example for two-phase commit section.

Aleksey Tsalolikhin <atsaloli.tech@xxxxxxxxx> · Wed, 1 Apr 2009 18:07:34 -0700

Hi.  We're trying to implement two-phase commit and did not find a
complete working example in the manual.  We found examples of the
separate pieces, but not the sequence in which to put them together.

Then we found this text,

  "PREPARE TRANSACTION is used in place of regular COMMIT to perform
the 1st phase, COMMIT PREPARED and ROLLBACK PREPARED perform the final
2nd phase commit or abort."

I'd like to offer two examples to illustrate that, for possible
inclusion in the manual:

1. Here's the sequence that two-phase commits:

  BEGIN;
  update mytable set a_col='something' where red_id=1000;
  PREPARE TRANSACTION 'foobar';
  COMMIT PREPARED 'foobar';

2. Here's the sequence that rolls back, leaving the table unchanged:

  BEGIN;
  update mytable set a_col='something' where red_id=1000;
  PREPARE TRANSACTION 'foobar';
  ROLLBACK PREPARED 'foobar';

If there is somebody on this list involved with editing the manual, this message
is for you.  :)    Examples make new things clearer, and easier to learn.

Just a suggestion.  :)

Best,
Aleksey

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