Fix crash on create statistics with non-RangeVar type pt2 (#8227)

Fixes #8225 
very similar to #8213 
Also the error message changed between pg18rc1 and pg18.0

src/backend/distributed/deparser/qualify_statistics_stmt.c

@@ -34,7 +34,14 @@ QualifyCreateStatisticsStmt(Node *node)
 {
 	CreateStatsStmt *stmt = castNode(CreateStatsStmt, node);
 
-	RangeVar *relation = (RangeVar *) linitial(stmt->relations);
+	Node *relationNode = (Node *) linitial(stmt->relations);
+
+	if (!IsA(relationNode, RangeVar))
+	{
+		return;
+	}
+
+	RangeVar *relation = (RangeVar *) relationNode;
 
 	if (relation->schemaname == NULL)
 	{

src/test/regress/expected/pg18.out

@@ -6,10 +6,15 @@ SELECT substring(:'server_version', '\d+')::int >= 18 AS server_version_ge_18
 \gset
 -- test invalid statistics
 -- behavior is same among PG versions, error message differs
--- relevant PG18 commit: 3eea4dc2c7
+-- relevant PG18 commit: 3eea4dc2c7, 38883916e
 CREATE STATISTICS tst ON a FROM (VALUES (x)) AS foo;
-ERROR:  cannot create statistics on the specified relation
-DETAIL:  CREATE STATISTICS only supports tables, foreign tables and materialized views.
+ERROR:  CREATE STATISTICS only supports relation names in the FROM clause
+CREATE FUNCTION tftest(int) returns table(a int, b int) as $$
+SELECT $1, $1+i FROM generate_series(1,5) g(i);
+$$ LANGUAGE sql IMMUTABLE STRICT;
+CREATE STATISTICS alt_stat2 ON a FROM tftest(1);
+ERROR:  CREATE STATISTICS only supports relation names in the FROM clause
+DROP FUNCTION tftest;
 \if :server_version_ge_18
 \else
 \q

src/test/regress/expected/pg18_0.out

@@ -6,9 +6,15 @@ SELECT substring(:'server_version', '\d+')::int >= 18 AS server_version_ge_18
 \gset
 -- test invalid statistics
 -- behavior is same among PG versions, error message differs
--- relevant PG18 commit: 3eea4dc2c7
+-- relevant PG18 commit: 3eea4dc2c7, 38883916e
 CREATE STATISTICS tst ON a FROM (VALUES (x)) AS foo;
 ERROR:  only a single relation is allowed in CREATE STATISTICS
+CREATE FUNCTION tftest(int) returns table(a int, b int) as $$
+SELECT $1, $1+i FROM generate_series(1,5) g(i);
+$$ LANGUAGE sql IMMUTABLE STRICT;
+CREATE STATISTICS alt_stat2 ON a FROM tftest(1);
+ERROR:  only a single relation is allowed in CREATE STATISTICS
+DROP FUNCTION tftest;
 \if :server_version_ge_18
 \else
 \q

src/test/regress/sql/pg18.sql

@@ -7,9 +7,15 @@ SELECT substring(:'server_version', '\d+')::int >= 18 AS server_version_ge_18
 
 -- test invalid statistics
 -- behavior is same among PG versions, error message differs
--- relevant PG18 commit: 3eea4dc2c7
+-- relevant PG18 commit: 3eea4dc2c7, 38883916e
 CREATE STATISTICS tst ON a FROM (VALUES (x)) AS foo;
 
+CREATE FUNCTION tftest(int) returns table(a int, b int) as $$
+SELECT $1, $1+i FROM generate_series(1,5) g(i);
+$$ LANGUAGE sql IMMUTABLE STRICT;
+CREATE STATISTICS alt_stat2 ON a FROM tftest(1);
+DROP FUNCTION tftest;
+
 \if :server_version_ge_18
 \else
 \q