"Mikheev, Vadim" <vmikheev@SECTORBASE.COM> writes:
>> I'm not sure that the time to do projection is short though
>> --- what if there are arbitrary user-defined functions in the quals
>> or the projection targetlist?
> Well, while we are on this subject I finally should say about issue
> bothered me for long time: only "simple" functions should be allowed
> to deal with data in shared buffers directly. "Simple" means: no SQL
> queries there. Why? One reason: we hold shlock on buffer while doing
> seqscan qual - what if qual' SQL queries will try to acquire exclock
> on the same buffer?
I think we're there already: AFAICT, user-specified quals and
projections are done after dropping the buffer shlock. (Yes, I know
there's a HeapKeyTest inside heapgettup, but user quals don't get
done there.) We do still hold a pin, but that seems OK to me.
regards, tom lane
