On Sun, Feb 09, 2020 at 08:01:26PM -0800, Andres Freund wrote: > Ugh, that indeed looks wrong. Did you check whether it can actively > cause wrong query results? If so, did you do theoretically, or got to a > query returning wrong results?
Actually .. I can "theoretically" prove that there's no wrong results from that patch...since in that file it has no effect, the tested variables being zeroed few lines earlier: @@ -499,51 +499,60 @@ buildSubPlanHash(SubPlanState *node, ExprContext *econtext) * node->hashtable = NULL; * node->hashnulls = NULL; node->havehashrows = false; node->havenullrows = false; nbuckets = (long) Min(planstate->plan->plan_rows, (double) LONG_MAX); if (nbuckets < 1) nbuckets = 1; - node->hashtable = BuildTupleHashTable(node->parent, - node->descRight, - ncols, - node->keyColIdx, - node->tab_eq_funcoids, - node->tab_hash_funcs, - nbuckets, - 0, - node->hashtablecxt, - node->hashtempcxt, - false); *+ if (node->hashtable) + ResetTupleHashTable(node->hashtable); + else + node->hashtable = BuildTupleHashTableExt(node->parent, ... *+ if (node->hashnulls) + ResetTupleHashTable(node->hashtable); + else + node->hashnulls = BuildTupleHashTableExt(node->parent, + node->descRight,