ignore_is_not_null_base_quals_on_not_null_columns.patch

diff --git a/src/backend/optimizer/plan/initsplan.c b/src/backend/optimizer/plan/initsplan.c
index b31d892121..277314c8cb 100644
--- a/src/backend/optimizer/plan/initsplan.c
+++ b/src/backend/optimizer/plan/initsplan.c
@@ -2618,6 +2618,50 @@ check_redundant_nullability_qual(PlannerInfo *root, Node *clause)
 	return false;
 }
 
+/*
+ * add_baserestrictinfo_to_rel
+ *		Add 'restrictinfo' as a baserestrictinfo to the base relation denoted by
+ *		'relid' with some prechecks to try to determine if the qual is always
+ *		true, in which case we ignore it rather than add it.
+ */
+static void
+add_baserestrictinfo_to_rel(PlannerInfo *root, Index relid,
+							RestrictInfo *restrictinfo)
+{
+	RelOptInfo *rel = find_base_rel(root, relid);
+
+	Assert(bms_membership(restrictinfo->required_relids) == BMS_SINGLETON);
+
+	/* Any IS NOT NULL qual on a NOT NULL column is always true */
+	if (IsA(restrictinfo->clause, NullTest))
+	{
+		NullTest *nulltest = (NullTest *) restrictinfo->clause;
+
+		if (nulltest->nulltesttype == IS_NOT_NULL && IsA(nulltest->arg, Var))
+		{
+			Var *var = (Var *) nulltest->arg;
+
+			Assert(var->varno == rel->relid);
+
+			/* don't add the qual as system columns cannot be NULL */
+			if (var->varattno < 0)
+				return;
+
+			/* don't add the IS NOT NULL when the column is defined NOT NULL */
+			if (var->varattno > 0 &&
+				bms_is_member(var->varattno, rel->notnullattnums))
+				return;
+		}
+	}
+
+	/* Add clause to rel's restriction list */
+	rel->baserestrictinfo = lappend(rel->baserestrictinfo, restrictinfo);
+
+	/* Update security level info */
+	rel->baserestrict_min_security = Min(rel->baserestrict_min_security,
+										 restrictinfo->security_level);
+}
+
 /*
  * distribute_restrictinfo_to_rels
  *	  Push a completed RestrictInfo into the proper restriction or join
@@ -2633,57 +2677,39 @@ distribute_restrictinfo_to_rels(PlannerInfo *root,
 {
 	Relids		relids = restrictinfo->required_relids;
 	RelOptInfo *rel;
+	int			relid;
 
-	switch (bms_membership(relids))
+	if (relids == NULL)
 	{
-		case BMS_SINGLETON:
-
-			/*
-			 * There is only one relation participating in the clause, so it
-			 * is a restriction clause for that relation.
-			 */
-			rel = find_base_rel(root, bms_singleton_member(relids));
-
-			/* Add clause to rel's restriction list */
-			rel->baserestrictinfo = lappend(rel->baserestrictinfo,
-											restrictinfo);
-			/* Update security level info */
-			rel->baserestrict_min_security = Min(rel->baserestrict_min_security,
-												 restrictinfo->security_level);
-			break;
-		case BMS_MULTIPLE:
-
-			/*
-			 * The clause is a join clause, since there is more than one rel
-			 * in its relid set.
-			 */
-
-			/*
-			 * Check for hashjoinable operators.  (We don't bother setting the
-			 * hashjoin info except in true join clauses.)
-			 */
-			check_hashjoinable(restrictinfo);
+		/*
+		 * clause references no rels, and therefore we have no place to
+		 * attach it.  Shouldn't get here if callers are working properly.
+		 */
+		elog(ERROR, "cannot cope with variable-free clause");
+	}
+	else if (bms_get_singleton_member(relids, &relid))
+		add_baserestrictinfo_to_rel(root, relid, restrictinfo);
+	else
+	{
+		/*
+		 * The clause is a join clause, since there is more than one rel in
+		 * its relid set.
+		 */
 
-			/*
-			 * Likewise, check if the clause is suitable to be used with a
-			 * Memoize node to cache inner tuples during a parameterized
-			 * nested loop.
-			 */
-			check_memoizable(restrictinfo);
+		/*
+		 * Check for hashjoinable operators.  (We don't bother setting the
+		 * hashjoin info except in true join clauses.)
+		 */
+		check_hashjoinable(restrictinfo);
 
-			/*
-			 * Add clause to the join lists of all the relevant relations.
-			 */
-			add_join_clause_to_rels(root, restrictinfo, relids);
-			break;
-		default:
+		/*
+		 * Likewise, check if the clause is suitable to be used with a Memoize
+		 * node to cache inner tuples during a parameterized nested loop.
+		 */
+		check_memoizable(restrictinfo);
 
-			/*
-			 * clause references no rels, and therefore we have no place to
-			 * attach it.  Shouldn't get here if callers are working properly.
-			 */
-			elog(ERROR, "cannot cope with variable-free clause");
-			break;
+		/* Add clause to the join lists of all the relevant relations. */
+		add_join_clause_to_rels(root, restrictinfo, relids);
 	}
 }
 
diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index 39932d3c2d..d810ad8127 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -163,6 +163,15 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
 	rel->attr_widths = (int32 *)
 		palloc0((rel->max_attr - rel->min_attr + 1) * sizeof(int32));
 
+	/* record which columns are defined as NOT NULL */
+	for (int i = 0; i < relation->rd_att->natts; i++)
+	{
+		FormData_pg_attribute *attr = &relation->rd_att->attrs[i];
+
+		if (attr->attnotnull)
+			rel->notnullattnums = bms_add_member(rel->notnullattnums, attr->attnum);
+	}
+
 	/*
 	 * Estimate relation size --- unless it's an inheritance parent, in which
 	 * case the size we want is not the rel's own size but the size of its
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index c17b53f7ad..851a4513a9 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -913,6 +913,8 @@ typedef struct RelOptInfo
 	Relids	   *attr_needed pg_node_attr(read_write_ignore);
 	/* array indexed [min_attr .. max_attr] */
 	int32	   *attr_widths pg_node_attr(read_write_ignore);
+	/* zero-based set containing attnums of NOT NULL columns */
+	Bitmapset *notnullattnums;
 	/* relids of outer joins that can null this baserel */
 	Relids		nulling_relids;
 	/* LATERAL Vars and PHVs referenced by rel */