Fix for not updating any columns

Author: Mytherin

src/storage/postgres_merge_into.cpp

@@ -32,6 +32,11 @@ unique_ptr<MergeIntoOperator> PostgresPlanMergeIntoAction(PostgresCatalog &catal
 
 	switch (action.action_type) {
 	case MergeActionType::MERGE_UPDATE: {
+		if (action.columns.empty()) {
+			// not updating any columns
+			result->action_type = MergeActionType::MERGE_DO_NOTHING;
+			break;
+		}
 		LogicalUpdate update(op.table);
 		for (auto &def : op.bound_defaults) {
 			update.bound_defaults.push_back(def->Copy());

src/storage/postgres_update.cpp

@@ -46,16 +46,14 @@ string CreateUpdateTable(const string &name, PostgresTableEntry &table, const ve
 	result = "CREATE LOCAL TEMPORARY TABLE " + PostgresUtils::QuotePostgresIdentifier(name);
 	result += "(";
 	for (idx_t i = 0; i < index.size(); i++) {
-		if (i > 0) {
-			result += ", ";
-		}
 		auto &column_name = table.postgres_names[index[i].index];
 		auto &col = table.GetColumn(LogicalIndex(index[i].index));
 		result += KeywordHelper::WriteQuoted(column_name, '"');
 		result += " ";
 		result += PostgresUtils::TypeToString(col.GetType());
+		result += ", ";
 	}
-	result += ", __page_id_string VARCHAR) ON COMMIT DROP;";
+	result += "__page_id_string VARCHAR) ON COMMIT DROP;";
 	return result;
 }