Re: Repeatable Read Isolation in SQL running via background worker

On Tue, Aug 14, 2018 at 11:18 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

> On Mon, Aug 13, 2018 at 10:52 AM, Jeremy Finzel <finzelj(at)gmail(dot)com> wrote:
> > On Thu, Aug 9, 2018 at 4:34 PM, Jeremy Finzel <finzelj(at)gmail(dot)com> wrote:
> >> I am using worker_spi as a model to run a SQL statement inside a
> >> background worker. From my browsing of the Postgres library, I believe
> that
> >> if I want repeatable read isolation level, the proper way for me to
> attain
> >> this is to add this line after StartTransactionCommand() in
> worker_spi_main:
> >>
> >> XactIsoLevel = XACT_REPEATABLE_READ;
>
> It's usually a good idea to only change GUCs through the GUC machinery
> i.e. use SetConfigOption().
>
> Are you using StartTransactionCommand() and CommitTransactionCommand()
> to manage transaction boundaries? If not, maybe you should.
>

Many thanks for the reply. Yes, I am using StartTransactionCommand and
Commit just like in worker_spi.c. Here is the relevant section of code:

SetCurrentStatementStartTimestamp();
StartTransactionCommand();
XactIsoLevel = XACT_REPEATABLE_READ;
SPI_connect();
PushActiveSnapshot(GetTransactionSnapshot());
pgstat_report_activity(STATE_RUNNING, buf.data);

/* We can now execute queries via SPI */
SPI_execute(buf.data, false, 0);

/*
* And finish our transaction.
*/
SPI_finish();
PopActiveSnapshot();
CommitTransactionCommand();

So if you are saying it would be better to use SetConfigOption() there I
will look into that. Thanks!
Jeremy