Re: More aggressive vacuuming of temporary tables - Mailing list pgsql-hackers

Andres Freund <andres@anarazel.de> writes:
> On 2020-09-08 15:24:54 -0400, Tom Lane wrote:
>> Andres Freund <andres@anarazel.de> writes:
>>> But now I do wonder why we need to know whether the command is top level
>>> or not? Why isn't the correct thing to instead look at what the current
>>> backend's xmin is? Seems like you could just replace
>>> *oldestXmin = XidFromFullTransactionId(ReadNextFullTransactionId());
>>> with
>>> *oldestXmin = MyProc->xmin;
>>> Assert(TransactionIdIsValid(*oldestXmin));

>> Ummm ... since VACUUM doesn't run inside a transaction, it won't be
>> advertising an xmin will it?

> We do run it in a transaction though:

Ah.  But still, this is not the semantics I want for VACUUM, because the
process xmin will involve other processes' behavior.  The point of the
change as far as I'm concerned is to ensure vacuuming of dead temp rows
independent of anything else in the system.

            regards, tom lane