add generic database exceptions

piccolo/engine/exceptions.py

@@ -1,2 +1,48 @@
 class TransactionError(Exception):
     pass
+
+
+###############################################################################
+# These are generic database Exceptions as specified in PEP 249:
+# https://peps.python.org/pep-0249/#exceptions
+
+
+class Error(Exception):
+    pass
+
+
+class InterfaceError(Error):
+    pass
+
+
+class DatabaseError(Error):
+    pass
+
+
+class DataError(DatabaseError):
+    pass
+
+
+class OperationalError(DatabaseError):
+    pass
+
+
+class IntegrityError(DatabaseError):
+    pass
+
+
+class InternalError(DatabaseError):
+    pass
+
+
+class ProgrammingError(DatabaseError):
+    pass
+
+
+class NotSupportedError(DatabaseError):
+    pass
+
+
+# TODO - write async context manager which maps these exceptions to generic
+# exceptions:
+# https://github.com/MagicStack/asyncpg/blob/master/asyncpg/exceptions/__init__.py

piccolo/engine/postgres.py

@@ -254,6 +254,12 @@ class PostgresEngine(Engine):
 
             >>> await MyTable.select().run(node="read_replica_1")
 
+    :param use_generic_exceptions:
+        Each database driver raises different exceptions. If you want to make
+        your code portable across different databases (e.g. SQLite and
+        Postgres), set this to ``True``. All exceptions raised by the database
+        driver are converted to generic Piccolo exceptions.
+
     """  # noqa: E501
 
     __slots__ = (
@@ -263,6 +269,7 @@ class PostgresEngine(Engine):
         "extra_nodes",
         "pool",
         "transaction_connection",
+        "use_generic_exceptions",
     )
 
     engine_type = "postgres"
@@ -274,10 +281,12 @@ def __init__(
         extensions: t.Sequence[str] = ("uuid-ossp",),
         log_queries: bool = False,
         extra_nodes: t.Dict[str, PostgresEngine] = None,
+        use_generic_exceptions: bool = False,
     ) -> None:
         if extra_nodes is None:
             extra_nodes = {}
 
+        self.use_generic_exceptions = use_generic_exceptions
         self.config = config
         self.extensions = extensions
         self.log_queries = log_queries