Deduplicate column names from postgres_query

src/include/postgres_utils.hpp

@@ -106,6 +106,8 @@ class PostgresUtils {
 	static PostgresQueryMode ExtractQueryMode(Value &value);
 	static PostgresCatalog &GetCatalogByName(ClientContext &context, const std::string &name);
 
+	static void DeduplicateColumns(vector<Identifier> &names);
+
 private:
 	static mutex libpq_init_lock;
 	static bool libpq_connect_succeeded_at_least_once;

src/postgres_query.cpp

@@ -206,9 +206,10 @@ static unique_ptr<FunctionData> PGQueryBind(ClientContext &context, TableFunctio
 		result->postgres_types.push_back(postgres_type);
 		return_types.emplace_back(converted_type);
 		char *name_ptr = PQfname(describe_prepared, c);
-		string name = name_ptr ? name_ptr : StringUtil::Format("unnamed_%llu", c);
+		string name = name_ptr ? name_ptr : "unnamed";
 		names.emplace_back(name);
 	}
+	PostgresUtils::DeduplicateColumns(names);
 	int nparams = PQnparams(describe_prepared);
 	if (nparams != param_values.size()) {
 		throw BinderException("Incorrect number of parameters specified, expected: %d, actual: %zu, query: \"%s\"",

src/postgres_utils.cpp

@@ -781,4 +781,24 @@ PostgresCatalog &PostgresUtils::GetCatalogByName(ClientContext &context, const s
 	return catalog.Cast<PostgresCatalog>();
 }
 
+void PostgresUtils::DeduplicateColumns(vector<Identifier> &names) {
+	identifier_map_t<idx_t> name_map;
+	for (auto &column_name : names) {
+		if (name_map.find(column_name) == name_map.end()) {
+			// Name does not exist yet
+			name_map[column_name]++;
+		} else {
+			// Name already exists, we add _x where x is the repetition number
+			Identifier new_column_name(column_name + "_" + std::to_string(name_map[column_name]));
+			while (name_map.find(new_column_name) != name_map.end()) {
+				// This name is already here due to a previous definition
+				name_map[column_name]++;
+				new_column_name = Identifier(column_name + "_" + std::to_string(name_map[column_name]));
+			}
+			column_name = new_column_name;
+			name_map[new_column_name]++;
+		}
+	}
+}
+
 } // namespace duckdb

test/sql/scanner/postgres_query.test

@@ -342,5 +342,19 @@ WHERE query = 'SELECT "brand" FROM (SELECT * FROM cars WHERE color=''red'') AS _
 statement ok
 CALL disable_logging()
 
+# duplicate column names
+
+query III
+FROM postgres_query('s1', 'SELECT 41, 42, 43')
+----
+41	42	43
+
+query I
+SELECT column_name FROM (DESCRIBE FROM postgres_query('s1', 'SELECT 41, 42, 43'))
+----
+?column?
+?column?_1
+?column?_2
+
 statement ok
 DETACH s1

test/sql/storage/limit_parallel_bug.test → test/sql/storage/limit_parallel_bug.test_slow

@@ -1,4 +1,4 @@
-# name: test/sql/storage/limit_parallel_bug.test
+# name: test/sql/storage/limit_parallel_bug.test_slow
 # description: Test LIMIT bug with parallelism (issues #380, #395)
 # group: [storage]