From 70c9bc03395fc372e1451bd1bc47c737bd0a44d4 Mon Sep 17 00:00:00 2001 From: Mike Bayer Date: Wed, 2 Oct 2019 11:20:58 -0400 Subject: Add max_identifier_length parameter; warn for Oracle Added new :func:`.create_engine` parameter :paramref:`.create_engine.max_identifier_length`. This overrides the dialect-coded "max identifier length" in order to accommodate for databases that have recently changed this length and the SQLAlchemy dialect has not yet been adjusted to detect for that version. This parameter interacts with the existing :paramref:`.create_engine.label_length` parameter in that it establishes the maximum (and default) value for anonymously generated labels. The Oracle dialect now emits a warning if Oracle version 12.2 or greater is used, and the :paramref:`.create_engine.max_identifier_length` parameter is not set. The version in this specific case defaults to that of the "compatibility" version set in the Oracle server configuration, not the actual server version. In version 1.4, the default max_identifier_length for 12.2 or greater will move to 128 characters. In order to maintain forwards compatibility, applications should set :paramref:`.create_engine.max_identifier_length` to 30 in order to maintain the same length behavior, or to 128 in order to test the upcoming behavior. This length determines among other things how generated constraint names are truncated for statements like ``CREATE CONSTRAINT`` and ``DROP CONSTRAINT``, which means a the new length may produce a name-mismatch against a name that was generated with the old length, impacting database migrations. Fixes: #4857 Change-Id: Ib62efb00c6180c375869029b57353d90385d7950 --- lib/sqlalchemy/engine/create.py | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) (limited to 'lib/sqlalchemy/engine/create.py') diff --git a/lib/sqlalchemy/engine/create.py b/lib/sqlalchemy/engine/create.py index 43378f24e..ed3d452e0 100644 --- a/lib/sqlalchemy/engine/create.py +++ b/lib/sqlalchemy/engine/create.py @@ -260,7 +260,15 @@ def create_engine(url, **kwargs): the size of dynamically generated column labels to that many characters. If less than 6, labels are generated as "_(counter)". If ``None``, the value of - ``dialect.max_identifier_length`` is used instead. + ``dialect.max_identifier_length``, which may be affected via the + :paramref:`.create_engine.max_identifier_length` parameter, + is used instead. The value of :paramref:`.create_engine.label_length` + may not be larger than that of + :paramref:`.create_engine.max_identfier_length`. + + .. seealso:: + + :paramref:`.create_engine.max_identifier_length` :param listeners: A list of one or more :class:`~sqlalchemy.interfaces.PoolListener` objects which will @@ -271,6 +279,21 @@ def create_engine(url, **kwargs): "sqlalchemy.engine" logger. Defaults to a hexstring of the object's id. + :param max_identifier_length: integer; override the max_identifier_length + determined by the dialect. if ``None`` or zero, has no effect. This + is the database's configured maximum number of characters that may be + used in a SQL identifier such as a table name, column name, or label + name. All dialects determine this value automatically, however in the + case of a new database version for which this value has changed but + SQLAlchemy's dialect has not been adjusted, the value may be passed + here. + + .. versionadded:: 1.3.9 + + .. seealso:: + + :paramref:`.create_engine.label_length` + :param max_overflow=10: the number of connections to allow in connection pool "overflow", that is connections that can be opened above and beyond the pool_size setting, which defaults -- cgit v1.2.1