Fix PlanRowMark/ExecRowMark structures to handle inheritance correctly.

In an inherited UPDATE/DELETE, each target table has its own subplan,
because it might have a column set different from other targets.  This
means that the resjunk columns we add to support EvalPlanQual might be
at different physical column numbers in each subplan.  The EvalPlanQual
rewrite I did for 9.0 failed to account for this, resulting in possible
misbehavior or even crashes during concurrent updates to the same row,
as seen in a recent report from Gordon Shannon.  Revise the data structure
so that we track resjunk column numbers separately for each subplan.

I also chose to move responsibility for identifying the physical column
numbers back to executor startup, instead of assuming that numbers derived
during preprocess_targetlist would stay valid throughout subsequent
massaging of the plan.  That's a bit slower, so we might want to consider
undoing it someday; but it would complicate the patch considerably and
didn't seem justifiable in a bug fix that has to be back-patched to 9.0.

1 files changed, 22 insertions, 20 deletions

diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 969938130ec..f4b2b16b69e 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -701,7 +701,8 @@ ExecModifyTable(ModifyTableState *node)
 				estate->es_result_relation_info++;
 				subplanstate = node->mt_plans[node->mt_whichplan];
 				junkfilter = estate->es_result_relation_info->ri_junkFilter;
-				EvalPlanQualSetPlan(&node->mt_epqstate, subplanstate->plan);
+				EvalPlanQualSetPlan(&node->mt_epqstate, subplanstate->plan,
+									node->mt_arowmarks[node->mt_whichplan]);
 				continue;
 			}
 			else
@@ -815,10 +816,11 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 	mtstate->ps.targetlist = NIL;		/* not actually used */
 
 	mtstate->mt_plans = (PlanState **) palloc0(sizeof(PlanState *) * nplans);
+	mtstate->mt_arowmarks = (List **) palloc0(sizeof(List *) * nplans);
 	mtstate->mt_nplans = nplans;
 	mtstate->operation = operation;
-	/* set up epqstate with dummy subplan pointer for the moment */
-	EvalPlanQualInit(&mtstate->mt_epqstate, estate, NULL, node->epqParam);
+	/* set up epqstate with dummy subplan data for the moment */
+	EvalPlanQualInit(&mtstate->mt_epqstate, estate, NULL, NIL, node->epqParam);
 	mtstate->fireBSTriggers = true;
 
 	/* For the moment, assume our targets are exactly the global result rels */
@@ -840,11 +842,6 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 	}
 	estate->es_result_relation_info = NULL;
 
-	/* select first subplan */
-	mtstate->mt_whichplan = 0;
-	subplan = (Plan *) linitial(node->plans);
-	EvalPlanQualSetPlan(&mtstate->mt_epqstate, subplan);
-
 	/*
 	 * Initialize RETURNING projections if needed.
 	 */
@@ -908,8 +905,7 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 	foreach(l, node->rowMarks)
 	{
 		PlanRowMark *rc = (PlanRowMark *) lfirst(l);
-		ExecRowMark *erm = NULL;
-		ListCell   *lce;
+		ExecRowMark *erm;
 
 		Assert(IsA(rc, PlanRowMark));
 
@@ -917,20 +913,26 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 		if (rc->isParent)
 			continue;
 
-		foreach(lce, estate->es_rowMarks)
+		/* find ExecRowMark (same for all subplans) */
+		erm = ExecFindRowMark(estate, rc->rti);
+
+		/* build ExecAuxRowMark for each subplan */
+		for (i = 0; i < nplans; i++)
 		{
-			erm = (ExecRowMark *) lfirst(lce);
-			if (erm->rti == rc->rti)
-				break;
-			erm = NULL;
-		}
-		if (erm == NULL)
-			elog(ERROR, "failed to find ExecRowMark for PlanRowMark %u",
-				 rc->rti);
+			ExecAuxRowMark *aerm;
 
-		EvalPlanQualAddRowMark(&mtstate->mt_epqstate, erm);
+			subplan = mtstate->mt_plans[i]->plan;
+			aerm = ExecBuildAuxRowMark(erm, subplan->targetlist);
+			mtstate->mt_arowmarks[i] = lappend(mtstate->mt_arowmarks[i], aerm);
+		}
 	}
 
+	/* select first subplan */
+	mtstate->mt_whichplan = 0;
+	subplan = (Plan *) linitial(node->plans);
+	EvalPlanQualSetPlan(&mtstate->mt_epqstate, subplan,
+						mtstate->mt_arowmarks[0]);
+
 	/*
 	 * Initialize the junk filter(s) if needed.  INSERT queries need a filter
 	 * if there are any junk attrs in the tlist.  UPDATE and DELETE always