Follow-up fix for Redshift: don't query pg_enum in older postgres versions

src/include/storage/postgres_type_set.hpp

@@ -25,7 +25,7 @@ class PostgresTypeSet : public PostgresInSchemaSet {
 public:
 	optional_ptr<CatalogEntry> CreateType(ClientContext &context, CreateTypeInfo &info);
 
-	static string GetInitializeEnumsQuery();
+	static string GetInitializeEnumsQuery(PostgresVersion version);
 	static string GetInitializeCompositesQuery();
 
 protected:

src/storage/postgres_schema_set.cpp

@@ -5,6 +5,7 @@
 #include "storage/postgres_transaction.hpp"
 #include "duckdb/parser/parsed_data/create_schema_info.hpp"
 #include "storage/postgres_table_set.hpp"
+#include "storage/postgres_catalog.hpp"
 
 namespace duckdb {
 
@@ -40,9 +41,11 @@ ORDER BY oid;
 }
 
 void PostgresSchemaSet::LoadEntries(ClientContext &context) {
+	auto &pg_catalog = catalog.Cast<PostgresCatalog>();
+	auto pg_version = pg_catalog.GetPostgresVersion();
 	string schema_query = PostgresSchemaSet::GetInitializeQuery();
 	string tables_query = PostgresTableSet::GetInitializeQuery();
-	string enum_types_query = PostgresTypeSet::GetInitializeEnumsQuery();
+	string enum_types_query = PostgresTypeSet::GetInitializeEnumsQuery(pg_version);
 	string composite_types_query = PostgresTypeSet::GetInitializeCompositesQuery();
 	string index_query = PostgresIndexSet::GetInitializeQuery();
 

src/storage/postgres_type_set.cpp

@@ -20,7 +20,15 @@ PostgresTypeSet::PostgresTypeSet(PostgresSchemaEntry &schema, unique_ptr<Postgre
       composite_type_result(std::move(composite_type_result_p)) {
 }
 
-string PostgresTypeSet::GetInitializeEnumsQuery() {
+string PostgresTypeSet::GetInitializeEnumsQuery(PostgresVersion version) {
+	if (version.major_v < 8 || (version.major_v == 8 && version.minor_v < 3)) {
+		// pg_enum support has been present since v8.3 - https://www.postgresql.org/docs/8.3/catalog-pg-enum.html
+		// for older postgres versions we don't support enums instead
+		return R"(
+SELECT 0 AS oid, 0 AS enumtypid, '' AS typname, '' AS enumlabel
+LIMIT 0;
+)";
+	}
 	return R"(
 SELECT n.oid, enumtypid, typname, enumlabel
 FROM pg_enum e