> @@ -234,6 +236,21 @@ index_beginscan(Relation heapRelation, > scan->heapRelation = heapRelation; > scan->xs_snapshot = snapshot; > > + /* > + * If the index supports recheck, make sure that index tuple is saved > + * during index scans. > + * > + * XXX Ideally, we should look at all indexes on the table and check if > + * WARM is at all supported on the base table. If WARM is not supported > + * then we don't need to do any recheck. RelationGetIndexAttrBitmap() does > + * do that and sets rd_supportswarm after looking at all indexes. But we > + * don't know if the function was called earlier in the session when we're > + * here. We can't call it now because there exists a risk of causing > + * deadlock. > + */ > + if (indexRelation->rd_amroutine->amrecheck) > + scan->xs_want_itup = true; > + > return scan; > }
I didn't like this comment very much. But it's not necessary: you have already given relcache responsibility for setting rd_supportswarm. The only problem seems to be that you set it in RelationGetIndexAttrBitmap instead of RelationGetIndexList, but it's not clear to me why. I think if the latter function is in charge, then we can trust the flag more than the current situation.
I looked at this today. AFAICS we don't have access to rd_amroutine in RelationGetIndexList since we don't actually call index_open() in that function. Would it be safe to do that? I'll give it a shot, but thought of asking here first.
