Re: [PATCHES] COPY with no WAL, in certain circumstances

"Simon Riggs" <simon@2ndquadrant.com> writes:
> ...continuing this discussion about setting HEAP_XMIN_COMMITTED...

>> BTW, a sufficient counterexample for that kluge is that neither SPI or
>> SQL-function execution use a separate portal for invoked commands.

> What would the best/acceptable way be to test for this condition?

My opinion is that the only reliable answer would be to find a way not
to have to test.  Tuples entered by your own transaction are normally
considered good by tqual.c anyway, and thus I think we might be pretty
close to having it Just Work, but you'd have to go through all the cases
in tqual.c and see if any don't work.

The other point is that to make such an optimization you have to
consider the subtransaction history.  For WAL you only have to know that
the table will disappear if the top-level transaction fails, but to
pre-set commit bits requires being sure that the table will disappear
if the current subxact fails --- not the same thing at all.
        regards, tom lane