Re: New docs chapter on Transaction Management and related changes

On Wed, Nov 23, 2022 at 02:17:19AM -0600, Justin Pryzby wrote:
> On Tue, Nov 22, 2022 at 01:50:36PM -0500, Bruce Momjian wrote:
> > +
> > +  <para>
> > +   A more complex example with multiple nested subtransactions:
> > +<programlisting>
> > +BEGIN;
> > +    INSERT INTO table1 VALUES (1);
> > +    SAVEPOINT sp1;
> > +    INSERT INTO table1 VALUES (2);
> > +    SAVEPOINT sp2;
> > +    INSERT INTO table1 VALUES (3);
> > +    RELEASE SAVEPOINT sp2;
> > +    INSERT INTO table1 VALUES (4))); -- generates an error
> > +</programlisting>
> > +   In this example, the application requests the release of the savepoint
> > +   <literal>sp2</literal>, which inserted 3.  This changes the insert's
> > +   transaction context to <literal>sp1</literal>.  When the statement
> > +   attempting to insert value 4 generates an error, the insertion of 2 and
> > +   4 are lost because they are in the same, now-rolled back savepoint,
> > +   and value 3 is in the same transaction context.  The application can
> > +   now only choose one of these two commands, since all other commands
> > +   will be ignored with a warning:
> > +<programlisting>
> > +   ROLLBACK;
> > +   ROLLBACK TO SAVEPOINT sp1;
> > +</programlisting>
> > +   Choosing <command>ROLLBACK</command> will abort everything, including
> > +   value 1, whereas <command>ROLLBACK TO SAVEPOINT sp1</command> will retain
> > +   value 1 and allow the transaction to continue.
> > +  </para>
> 
> This mentions a warning, but what happens is actually an error:
> 
> postgres=!# select;
> ERROR:  current transaction is aborted, commands ignored until end of transaction block

Good point, new text:

       The application can now only choose one of these two commands,
       since all other commands will be ignored:

Updated patch attached.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Indecision is a decision.  Inaction is an action.  Mark Batterson