diff options
Diffstat (limited to 'lib/sqlalchemy')
| -rw-r--r-- | lib/sqlalchemy/dialects/mysql/base.py | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/lib/sqlalchemy/dialects/mysql/base.py b/lib/sqlalchemy/dialects/mysql/base.py index 8ead8f148..901849bb2 100644 --- a/lib/sqlalchemy/dialects/mysql/base.py +++ b/lib/sqlalchemy/dialects/mysql/base.py @@ -265,6 +265,45 @@ http://dev.mysql.com/doc/refman/5.0/en/create-index.html http://dev.mysql.com/doc/refman/5.0/en/create-table.html +.. _mysql_foreign_keys: + +MySQL Foreign Key Options +------------------------- + +MySQL does not support the foreign key arguments "DEFERRABLE", "INITIALLY", +or "MATCH". Using the ``deferrable`` or ``initially`` keyword argument with +:class:`.ForeignKeyConstraint` or :class:`.ForeignKey` will have the effect of +these keywords being ignored in a DDL expression along with a warning, however this behavior +**will change** in a future release. + +In order to use these keywords on a foreign key while having them ignored +on a MySQL backend, use a custom compile rule:: + + from sqlalchemy.ext.compiler import compiles + from sqlalchemy.schema import ForeignKeyConstraint + + @compiles(ForeignKeyConstraint, "mysql") + def process(element, compiler, **kw): + element.deferrable = element.initially = None + return compiler.visit_foreign_key_constraint(element, **kw) + +.. versionchanged:: 0.8.3 - the MySQL backend will emit a warning when the + the ``deferrable`` or ``initially`` keyword arguments of :class:`.ForeignKeyConstraint` + and :class:`.ForeignKey` are used. The arguments will no longer be + ignored in 0.9. + +The "MATCH" keyword is in fact more insidious, and in a future release will be +explicitly disallowed +by SQLAlchemy in conjunction with the MySQL backend. This argument is silently +ignored by MySQL, but in addition has the effect of ON UPDATE and ON DELETE options +also being ignored by the backend. Therefore MATCH should never be used with the +MySQL backend; as is the case with DEFERRABLE and INITIALLY, custom compilation +rules can be used to correct a MySQL ForeignKeyConstraint at DDL definition time. + +.. versionadded:: 0.8.3 - the MySQL backend will emit a warning when + the ``match`` keyword is used with :class:`.ForeignKeyConstraint` + or :class:`.ForeignKey`. This will be a :class:`.CompileError` in 0.9. + """ import datetime @@ -1607,6 +1646,23 @@ class MySQLDDLCompiler(compiler.DDLCompiler): qual, const) def define_constraint_deferrability(self, constraint): + if constraint.deferrable is not None: + util.warn("The 'deferrable' keyword will no longer be ignored by the " + "MySQL backend in 0.9 - please adjust so that this keyword is " + "not used in conjunction with MySQL.") + if constraint.initially is not None: + util.warn("The 'initially' keyword will no longer be ignored by the " + "MySQL backend in 0.9 - please adjust so that this keyword is " + "not used in conjunction with MySQL.") + + return "" + + + def define_constraint_match(self, constraint): + if constraint.match is not None: + util.warn("MySQL ignores the 'MATCH' keyword while at the same time " + "causes ON UPDATE/ON DELETE clauses to be ignored - " + "this will be an exception in 0.9.") return "" class MySQLTypeCompiler(compiler.GenericTypeCompiler): |