1 files changed, 29 insertions, 19 deletions

diff --git a/src/backend/utils/cache/partcache.c b/src/backend/utils/cache/partcache.c
index e35a43405eb..5757301d054 100644
--- a/src/backend/utils/cache/partcache.c
+++ b/src/backend/utils/cache/partcache.c
@@ -797,31 +797,38 @@ RelationGetPartitionQual(Relation rel)
  * get_partition_qual_relid
  *
  * Returns an expression tree describing the passed-in relation's partition
- * constraint. If there is no partition constraint returns NULL; this can
- * happen if the default partition is the only partition.
+ * constraint.
+ *
+ * If the relation is not found, or is not a partition, or there is no
+ * partition constraint, return NULL.  We must guard against the first two
+ * cases because this supports a SQL function that could be passed any OID.
+ * The last case can happen even if relispartition is true, when a default
+ * partition is the only partition.
  */
 Expr *
 get_partition_qual_relid(Oid relid)
 {
-	Relation	rel = heap_open(relid, AccessShareLock);
 	Expr	   *result = NULL;
-	List	   *and_args;
 
-	/* Do the work only if this relation is a partition. */
-	if (rel->rd_rel->relispartition)
+	/* Do the work only if this relation exists and is a partition. */
+	if (get_rel_relispartition(relid))
 	{
+		Relation	rel = relation_open(relid, AccessShareLock);
+		List	   *and_args;
+
 		and_args = generate_partition_qual(rel);
 
+		/* Convert implicit-AND list format to boolean expression */
 		if (and_args == NIL)
 			result = NULL;
 		else if (list_length(and_args) > 1)
 			result = makeBoolExpr(AND_EXPR, and_args, -1);
 		else
 			result = linitial(and_args);
-	}
 
-	/* Keep the lock. */
-	heap_close(rel, NoLock);
+		/* Keep the lock, to allow safe deparsing against the rel by caller. */
+		relation_close(rel, NoLock);
+	}
 
 	return result;
 }
@@ -845,7 +852,6 @@ generate_partition_qual(Relation rel)
 	MemoryContext oldcxt;
 	Datum		boundDatum;
 	bool		isnull;
-	PartitionBoundSpec *bound;
 	List	   *my_qual = NIL,
 			   *result = NIL;
 	Relation	parent;
@@ -859,8 +865,8 @@ generate_partition_qual(Relation rel)
 		return copyObject(rel->rd_partcheck);
 
 	/* Grab at least an AccessShareLock on the parent table */
-	parent = heap_open(get_partition_parent(RelationGetRelid(rel)),
-					   AccessShareLock);
+	parent = relation_open(get_partition_parent(RelationGetRelid(rel)),
+						   AccessShareLock);
 
 	/* Get pg_class.relpartbound */
 	tuple = SearchSysCache1(RELOID, RelationGetRelid(rel));
@@ -871,13 +877,17 @@ generate_partition_qual(Relation rel)
 	boundDatum = SysCacheGetAttr(RELOID, tuple,
 								 Anum_pg_class_relpartbound,
 								 &isnull);
-	if (isnull)
-		elog(ERROR, "null relpartbound for relation %u", RelationGetRelid(rel));
-	bound = castNode(PartitionBoundSpec,
-					 stringToNode(TextDatumGetCString(boundDatum)));
-	ReleaseSysCache(tuple);
+	if (!isnull)
+	{
+		PartitionBoundSpec *bound;
+
+		bound = castNode(PartitionBoundSpec,
+						 stringToNode(TextDatumGetCString(boundDatum)));
 
-	my_qual = get_qual_from_partbound(rel, parent, bound);
+		my_qual = get_qual_from_partbound(rel, parent, bound);
+	}
+
+	ReleaseSysCache(tuple);
 
 	/* Add the parent's quals to the list (if any) */
 	if (parent->rd_rel->relispartition)
@@ -903,7 +913,7 @@ generate_partition_qual(Relation rel)
 	MemoryContextSwitchTo(oldcxt);
 
 	/* Keep the parent locked until commit */
-	heap_close(parent, NoLock);
+	relation_close(parent, NoLock);
 
 	return result;
 }