diff options
Diffstat (limited to 'lib/sqlalchemy/schema.py')
| -rw-r--r-- | lib/sqlalchemy/schema.py | 53 |
1 files changed, 45 insertions, 8 deletions
diff --git a/lib/sqlalchemy/schema.py b/lib/sqlalchemy/schema.py index 75bbfd070..5f82a0200 100644 --- a/lib/sqlalchemy/schema.py +++ b/lib/sqlalchemy/schema.py @@ -806,7 +806,11 @@ class Column(SchemaItem, expression.ColumnClause): for fk in col.foreign_keys: col.foreign_keys.remove(fk) table.foreign_keys.remove(fk) - table.constraints.remove(fk.constraint) + if fk.constraint in table.constraints: + # this might have been removed + # already, if it's a composite constraint + # and more than one col being replaced + table.constraints.remove(fk.constraint) table._columns.replace(self) @@ -1019,7 +1023,20 @@ class ForeignKey(SchemaItem): return "ForeignKey(%r)" % self._get_colspec() def copy(self, schema=None): - """Produce a copy of this ForeignKey object.""" + """Produce a copy of this :class:`ForeignKey` object. + + The new :class:`ForeignKey` will not be bound + to any :class:`Column`. + + This method is usually used by the internal + copy procedures of :class:`Column`, :class:`Table`, + and :class:`MetaData`. + + :param schema: The returned :class:`ForeignKey` will + reference the original table and column name, qualified + by the given string schema name. + + """ return ForeignKey( self._get_colspec(schema=schema), @@ -1033,6 +1050,12 @@ class ForeignKey(SchemaItem): ) def _get_colspec(self, schema=None): + """Return a string based 'column specification' for this :class:`ForeignKey`. + + This is usually the equivalent of the string-based "tablename.colname" + argument first passed to the object's constructor. + + """ if schema: return schema + "." + self.column.table.name + \ "." + self.column.key @@ -1048,15 +1071,16 @@ class ForeignKey(SchemaItem): target_fullname = property(_get_colspec) def references(self, table): - """Return True if the given table is referenced by this ForeignKey.""" + """Return True if the given :class:`Table` is referenced by this :class:`ForeignKey`.""" return table.corresponding_column(self.column) is not None def get_referent(self, table): - """Return the column in the given table referenced by this ForeignKey. + """Return the :class:`.Column` in the given :class:`.Table` + referenced by this :class:`ForeignKey`. - Returns None if this ``ForeignKey`` does not reference the given - table. + Returns None if this :class:`ForeignKey` does not reference the given + :class:`Table`. """ @@ -1064,6 +1088,18 @@ class ForeignKey(SchemaItem): @util.memoized_property def column(self): + """Return the target :class:`.Column` referenced by this :class:`.ForeignKey`. + + If this :class:`ForeignKey` was created using a + string-based target column specification, this + attribute will on first access initiate a resolution + process to locate the referenced remote + :class:`.Column`. The resolution process traverses + to the parent :class:`.Column`, :class:`.Table`, and + :class:`.MetaData` to proceed - if any of these aren't + yet present, an error is raised. + + """ # ForeignKey inits its remote column as late as possible, so tables # can be defined without dependencies if isinstance(self._colspec, basestring): @@ -1108,8 +1144,9 @@ class ForeignKey(SchemaItem): if _get_table_key(tname, schema) not in parenttable.metadata: raise exc.NoReferencedTableError( - "Could not find table '%s' with which to generate a " - "foreign key" % tname) + "Foreign key assocated with column '%s' could not find " + "table '%s' with which to generate a " + "foreign key to target column '%s'" % (self.parent, tname, colname)) table = Table(tname, parenttable.metadata, mustexist=True, schema=schema) |