Merge pull request #140 from Mytherin/aurorafix

Detect that we are connected with Aurora, and avoid running snapshot code with Aurora in general

Author: Mytherin

src/include/postgres_version.hpp

@@ -12,6 +12,8 @@
 
 namespace duckdb {
 
+enum class PostgresInstanceType { POSTGRES, AURORA };
+
 struct PostgresVersion {
 	PostgresVersion() {
 	}
@@ -22,6 +24,7 @@ struct PostgresVersion {
 	idx_t major_v = 0;
 	idx_t minor_v = 0;
 	idx_t patch_v = 0;
+	PostgresInstanceType type_v = PostgresInstanceType::POSTGRES;
 
 	inline bool operator<(const PostgresVersion &rhs) const {
 		if (major_v < rhs.major_v) {

src/postgres_connection.cpp

@@ -80,8 +80,11 @@ void PostgresConnection::Execute(const string &query) {
 }
 
 PostgresVersion PostgresConnection::GetPostgresVersion() {
-	auto result = Query("SHOW server_version;");
+	auto result = Query("SELECT CURRENT_SETTING('server_version'), (SELECT COUNT(*) FROM pg_settings WHERE name LIKE 'rds%')");
 	auto version = PostgresUtils::ExtractPostgresVersion(result->GetString(0, 0));
+	if (result->GetInt64(0, 1) > 0) {
+		version.type_v = PostgresInstanceType::AURORA;
+	}
 	return version;
 }
 

src/postgres_scanner.cpp

@@ -51,6 +51,9 @@ static void PostgresGetSnapshot(PostgresVersion version, PostgresBindData &bind_
 	unique_ptr<PostgresResult> result;
 	// by default disable snapshotting
 	bind_data.snapshot = string();
+	if (version.type_v == PostgresInstanceType::AURORA) {
+		return;
+	}
 	// reader threads can use the same snapshot
 	auto &con = bind_data.connection;
 	// pg_stat_wal_receiver was introduced in PostgreSQL 9.6
@@ -275,11 +278,12 @@ static unique_ptr<LocalTableFunctionState> GetLocalState(ClientContext &context,
 	}
 	local_state->column_ids = input.column_ids;
 
-	if (!bind_data.read_only) {
+	if (bind_data.read_only && bind_data.max_threads > 1) {
+		local_state->connection = PostgresScanConnect(bind_data.dsn, bind_data.snapshot);
+	} else {
 		// if we have made other modifications in this transaction we have to use the main connection
+		// alternatively, if we are only using a single thread to scan, we use the current connection as well
 		local_state->connection = PostgresConnection(bind_data.connection.GetConnection());
-	} else {
-		local_state->connection = PostgresScanConnect(bind_data.dsn, bind_data.snapshot);
 	}
 	local_state->filters = input.filters.get();
 	if (bind_data.pages_approx == 0 || bind_data.requires_materialization) {