Re: SPI: Correct way to rollback a subtransaction?

On 2/20/06, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> "Marko Kreen" <markokr(at)gmail(dot)com> writes:
> > BeginInternalSubTransaction(NULL);
> > res = SPI_connect();
> > if (res < 0)
> > elog(ERROR, "cannot connect to SPI");

> This seems like a pretty bad idea: if the SPI_connect fails you lose
> control without having unwound the subtransaction. That's unlikely,
> but still wrong.

But if I want the error to reach upper transaction? SPI_connect
failure does not seem a 'expected' situation to me.

Or will the started subtransaction corrupt some state?

> PG_CATCH();
> {
> /* we expect rollback to clean up inner SPI call */
> RollbackAndReleaseCurrentSubTransaction();
> FlushErrorState();
> res = -1; /* remember failure */
> }
> PG_END_TRY();
>
> Check the abort-subtrans path but I think it gets you out of the nested
> SPI call. (Because pl_exec.c wants to preserve an already-opened SPI
> call, it has to go out of its way to undo this via SPI_restore_connection.
> I *think* you don't need that here but am too lazy to check for sure.
> Anyway it'll be good practice for you to figure it out for yourself ;-))

Thank you for hints. The RollbackAndReleaseCurrentSubTransaction()
seems to call AbortSubTransaction->AtEOSubXact_SPI() only if the
transaction is TBLOCK_SUBINPROGRESS, As SERIALIZABLE seems to
thow simple elog(ERROR, ...) [executor/execMain.c], and error
handling also does not seem to touch transaction state, it seems
calling SPI_finish() is not needed.

Correct? (Yes, I'm newbie in core code...)

--
marko