Re: [HACKERS] Big IN() clauses etc : feature proposal

[Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>]

"Jim C. Nasby" <jnasby(at)pervasive(dot)com> writes:
> On Tue, May 09, 2006 at 03:13:01PM -0400, Tom Lane wrote:
>> PFC <lists(at)peufeu(dot)com> writes:
>>> Fun thing is, the rowcount from a temp table (which is the problem here)  
>>> should be available without ANALYZE ; as the temp table is not concurrent,  
>>> it would be simple to inc/decrement a counter on INSERT/DELETE...
>> 
>> No, because MVCC rules still apply.

> But can anything ever see more than one version of what's in the table?

Yes, because there can be more than one active snapshot within a single
transaction (think about volatile functions in particular).

> Speaking of which, if a temp table is defined as ON COMMIT DROP or
> DELETE ROWS, there shouldn't be any need to store xmin/xmax, only
> cmin/cmax, correct?

No; you forgot about subtransactions.

			regards, tom lane