Add lazy evaluation of server_version_info

tests/integration/test_sqlalchemy_integration.py

@@ -497,3 +497,22 @@ def test_get_view_names_raises(trino_connection):
 
  with pytest.raises(sqla.exc.NoSuchTableError):
  sqla.inspect(engine).get_view_names(None)
+
+
+@pytest.mark.parametrize('trino_connection', ['system'], indirect=True)
+def test_version_is_lazy(trino_connection):
+ _, conn = trino_connection
+ result = conn.execute("SELECT 1")
+ result.fetchall()
+ num_queries = num_queries_containing_string(conn, "SELECT version()")
+ assert num_queries == 0
+ version_info = conn.dialect.server_version_info
+ assert isinstance(version_info, tuple)
+ num_queries = num_queries_containing_string(conn, "SELECT version()")
+ assert num_queries == 1
+
+
+def num_queries_containing_string(connection, query_string, num=3):
+ result = connection.execute("select query from system.runtime.queries order by query_id desc limit ?", num)
+ rows = result.fetchall()
+ return len(list(filter(lambda rec: query_string in rec[0], rows)))

trino/sqlalchemy/dialect.py

@@ -336,15 +336,20 @@ def has_sequence(self, connection: Connection, sequence_name: str, schema: str =
  """Trino has no support for sequence. Returns False indicate that given sequence does not exists."""
  return False
 
- def _get_server_version_info(self, connection: Connection) -> Any:
- query = "SELECT version()"
- try:
- res = connection.execute(sql.text(query))
- version = res.scalar()
- return tuple([version])
- except exc.ProgrammingError as e:
- logger.debug(f"Failed to get server version: {e.orig.message}")
- return None
+ @classmethod
+ def _get_server_version_info(cls, connection: Connection) -> Any:
+ def get_server_version_info(_):
+ query = "SELECT version()"
+ try:
+ res = connection.execute(sql.text(query))
+ version = res.scalar()
+ return tuple([version])
+ except exc.ProgrammingError as e:
+ logger.debug(f"Failed to get server version: {e.orig.message}")
+ return None
+
+ # We make the server_version_info be evaluated lazily
+ cls.server_version_info = property(get_server_version_info, lambda instance, value: None)
 
  def _raw_connection(self, connection: Union[Engine, Connection]) -> trino_dbapi.Connection:
  if isinstance(connection, Engine):