Heikki Linnakangas <[EMAIL PROTECTED]> writes: > Tom Lane wrote: >> It occurs to me that there's an actual bug here for catalog access. >> The code assumes that it can measure rs_nblocks only once and not worry >> about tuples added beyond that endpoint. But this is only true when >> using an MVCC-safe snapshot.
> You would only miss tuples inserted after you began the seqscan. After > you've began the scan, you're going to miss any tuples that are inserted > before the current position anyway, so stopping the scan early shouldn't > do any real harm. Good point. > It would only be a problem if you do something like: > heap_beginscan(...) > Lock > while(heap_getnext) ... > Unlock > And expect to see all tuples inserted before acquiring the lock. But that could be fixed by taking the lock before the heap_beginscan. Indeed it's hard to conceive of a situation where you'd want/need to take the lock afterward; in most cases the beginscan and the actual scan are right together. So I withdraw this complaint; it's complexity we don't need. I'll add a comment about the point though. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match