diff options
Diffstat (limited to 'lib/sqlalchemy/dialects/mysql/base.py')
| -rw-r--r-- | lib/sqlalchemy/dialects/mysql/base.py | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/lib/sqlalchemy/dialects/mysql/base.py b/lib/sqlalchemy/dialects/mysql/base.py index 2f85a3626..793e6566d 100644 --- a/lib/sqlalchemy/dialects/mysql/base.py +++ b/lib/sqlalchemy/dialects/mysql/base.py @@ -341,6 +341,29 @@ reflection will not include foreign keys. For these tables, you may supply a :ref:`mysql_storage_engines` +.. _mysql_unique_constraints: + +MySQL Unique Constraints and Reflection +--------------------------------------- + +SQLAlchemy supports both the :class:`.Index` construct with the +flag ``unique=True``, indicating a UNIQUE index, as well as the +:class:`.UniqueConstraint` construct, representing a UNIQUE constraint. +Both objects/syntaxes are supported by MySQL when emitting DDL to create +these constraints. However, MySQL does not have a unique constraint +construct that is separate from a unique index; that is, the "UNIQUE" +constraint on MySQL is equivalent to creating a "UNIQUE INDEX". + +When reflecting these constructs, the :meth:`.Inspector.get_indexes` +and the :meth:`.Inspector.get_unique_constraints` methods will **both** +return an entry for a UNIQUE index in MySQL. However, when performing +full table reflection using ``Table(..., autoload=True)``, +the :class:`.UniqueConstraint` construct is +**not** part of the fully reflected :class:`.Table` construct under any +circumstances; this construct is always represented by a :class:`.Index` +with the ``unique=True`` setting present in the :attr:`.Table.indexes` +collection. + .. _mysql_timestamp_null: |