Add new function planstate_tree_walker.

ExplainPreScanNode knows how to iterate over a generic tree of plan
states; factor that logic out into a separate walker function so that
other code, such as upcoming patches for parallel query, can also use
it.

Patch by me, reviewed by Tom Lane.

1 files changed, 3 insertions, 90 deletions

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 4f32400011f..f0d9e94eed2 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -55,10 +55,7 @@ static void ExplainOneQuery(Query *query, IntoClause *into, ExplainState *es,
 static void report_triggers(ResultRelInfo *rInfo, bool show_relname,
 				ExplainState *es);
 static double elapsed_time(instr_time *starttime);
-static void ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used);
-static void ExplainPreScanMemberNodes(List *plans, PlanState **planstates,
-						  Bitmapset **rels_used);
-static void ExplainPreScanSubPlans(List *plans, Bitmapset **rels_used);
+static bool ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used);
 static void ExplainNode(PlanState *planstate, List *ancestors,
 			const char *relationship, const char *plan_name,
 			ExplainState *es);
@@ -724,7 +721,7 @@ elapsed_time(instr_time *starttime)
  * This ensures that we don't confusingly assign un-suffixed aliases to RTEs
  * that never appear in the EXPLAIN output (such as inheritance parents).
  */
-static void
+static bool
 ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
 {
 	Plan	   *plan = planstate->plan;
@@ -764,91 +761,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used)
 			break;
 	}
 
-	/* initPlan-s */
-	if (planstate->initPlan)
-		ExplainPreScanSubPlans(planstate->initPlan, rels_used);
-
-	/* lefttree */
-	if (outerPlanState(planstate))
-		ExplainPreScanNode(outerPlanState(planstate), rels_used);
-
-	/* righttree */
-	if (innerPlanState(planstate))
-		ExplainPreScanNode(innerPlanState(planstate), rels_used);
-
-	/* special child plans */
-	switch (nodeTag(plan))
-	{
-		case T_ModifyTable:
-			ExplainPreScanMemberNodes(((ModifyTable *) plan)->plans,
-								  ((ModifyTableState *) planstate)->mt_plans,
-									  rels_used);
-			break;
-		case T_Append:
-			ExplainPreScanMemberNodes(((Append *) plan)->appendplans,
-									((AppendState *) planstate)->appendplans,
-									  rels_used);
-			break;
-		case T_MergeAppend:
-			ExplainPreScanMemberNodes(((MergeAppend *) plan)->mergeplans,
-								((MergeAppendState *) planstate)->mergeplans,
-									  rels_used);
-			break;
-		case T_BitmapAnd:
-			ExplainPreScanMemberNodes(((BitmapAnd *) plan)->bitmapplans,
-								 ((BitmapAndState *) planstate)->bitmapplans,
-									  rels_used);
-			break;
-		case T_BitmapOr:
-			ExplainPreScanMemberNodes(((BitmapOr *) plan)->bitmapplans,
-								  ((BitmapOrState *) planstate)->bitmapplans,
-									  rels_used);
-			break;
-		case T_SubqueryScan:
-			ExplainPreScanNode(((SubqueryScanState *) planstate)->subplan,
-							   rels_used);
-			break;
-		default:
-			break;
-	}
-
-	/* subPlan-s */
-	if (planstate->subPlan)
-		ExplainPreScanSubPlans(planstate->subPlan, rels_used);
-}
-
-/*
- * Prescan the constituent plans of a ModifyTable, Append, MergeAppend,
- * BitmapAnd, or BitmapOr node.
- *
- * Note: we don't actually need to examine the Plan list members, but
- * we need the list in order to determine the length of the PlanState array.
- */
-static void
-ExplainPreScanMemberNodes(List *plans, PlanState **planstates,
-						  Bitmapset **rels_used)
-{
-	int			nplans = list_length(plans);
-	int			j;
-
-	for (j = 0; j < nplans; j++)
-		ExplainPreScanNode(planstates[j], rels_used);
-}
-
-/*
- * Prescan a list of SubPlans (or initPlans, which also use SubPlan nodes).
- */
-static void
-ExplainPreScanSubPlans(List *plans, Bitmapset **rels_used)
-{
-	ListCell   *lst;
-
-	foreach(lst, plans)
-	{
-		SubPlanState *sps = (SubPlanState *) lfirst(lst);
-
-		ExplainPreScanNode(sps->planstate, rels_used);
-	}
+	return planstate_tree_walker(planstate, ExplainPreScanNode, rels_used);
 }
 
 /*