Fix crash in explain with append info for ShareInputScan nodes.

The issue occurs when ShareInputScan nodes are reused multiple times
during explain with append info in deparse_context_for_plan_tree().

Address that by marking only the producer of ShareInputScan with
the same share_id to prevent the crash.
This ensures proper handling of shared scan nodes during plan tree deparsing.

Authored-by: Zhang Mingli [email protected]

Author: avamingli

src/backend/cdb/cdbmutate.c

@@ -659,6 +659,8 @@ shareinput_save_producer(ShareInputScan *plan, ApplyShareInputContext *ctxt)
 		ctxt->shared_input_count = new_shared_input_count;
 	}
 
+	plan->ref_set = true;
+
 	Assert(ctxt->shared_plans[share_id] == NULL);
 	ctxt->shared_plans[share_id] = plan->scan.plan.lefttree;
 }

src/backend/nodes/copyfuncs.c

@@ -1262,6 +1262,7 @@ _copyShareInputScan(const ShareInputScan *from)
 	COPY_SCALAR_FIELD(this_slice_id);
 	COPY_SCALAR_FIELD(nconsumers);
 	COPY_SCALAR_FIELD(discard_output);
+	COPY_SCALAR_FIELD(ref_set);
 
 	return newnode;
 }

src/backend/nodes/outfuncs_common.c

@@ -398,6 +398,7 @@ _outShareInputScan(StringInfo str, const ShareInputScan *node)
 	WRITE_INT_FIELD(this_slice_id);
 	WRITE_INT_FIELD(nconsumers);
 	WRITE_BOOL_FIELD(discard_output);
+	WRITE_BOOL_FIELD(ref_set);
 
 	_outPlanInfo(str, (Plan *) node);
 }

src/backend/nodes/readfast.c

@@ -1002,6 +1002,7 @@ _readShareInputScan(void)
 	READ_INT_FIELD(this_slice_id);
 	READ_INT_FIELD(nconsumers);
 	READ_BOOL_FIELD(discard_output);
+	READ_BOOL_FIELD(ref_set);
 
 	ReadCommonPlan(&local_node->scan.plan);
 

src/backend/optimizer/plan/planshare.c

@@ -40,6 +40,7 @@ make_shareinputscan(PlannerInfo *root, Plan *inputplan)
 	sisc->this_slice_id = -1;
 	sisc->nconsumers = 0;
 	sisc->discard_output = false;
+	sisc->ref_set = false;
 
 	sisc->scan.plan.qual = NIL;
 	sisc->scan.plan.righttree = NULL;

src/backend/optimizer/plan/setrefs.c

@@ -387,6 +387,7 @@ set_plan_references(PlannerInfo *root, Plan *plan)
 	PlannerGlobal *glob = root->glob;
 	int			rtoffset = list_length(glob->finalrtable);
 	ListCell   *lc;
+	bool need_append_rel = true;
 
 #ifdef USE_ASSERT_CHECKING
 	/* 
@@ -422,6 +423,17 @@ set_plan_references(PlannerInfo *root, Plan *plan)
 		glob->finalrowmarks = lappend(glob->finalrowmarks, newrc);
 	}
 
+	/*
+	 * ShareInputScan nodes can be reused multiple times during execution, but this
+	 * causes a crash when explaining plans with append info in the function
+	 * deparse_context_for_plan_tree().
+	 *
+	 * To fix this, we only add appendrels for the producer ShareInputScan node of
+	 * a given share_id, rather than all nodes with the same share_id. 
+	 */
+	if (plan != NULL && IsA(plan, ShareInputScan))
+		need_append_rel = ((ShareInputScan *) plan)->ref_set;
+
 	/*
 	 * Adjust RT indexes of AppendRelInfos and add to final appendrels list.
 	 * We assume the AppendRelInfos were built during planning and don't need
@@ -431,6 +443,9 @@ set_plan_references(PlannerInfo *root, Plan *plan)
 	{
 		AppendRelInfo *appinfo = lfirst_node(AppendRelInfo, lc);
 
+		if (!need_append_rel)
+			break;
+
 		/* adjust RT indexes */
 		appinfo->parent_relid += rtoffset;
 		appinfo->child_relid += rtoffset;

src/include/nodes/plannodes.h

@@ -1245,6 +1245,9 @@ typedef struct ShareInputScan
 
 	/* Discard the scan output? True for ORCA CTE producer, false otherwise. */
 	bool        discard_output;
+
+	/* Could be set reference? */
+	bool		ref_set;
 } ShareInputScan;
 
 /* ----------------