diff options
Diffstat (limited to 'lib/sqlalchemy/sql/expression.py')
| -rw-r--r-- | lib/sqlalchemy/sql/expression.py | 48 |
1 files changed, 33 insertions, 15 deletions
diff --git a/lib/sqlalchemy/sql/expression.py b/lib/sqlalchemy/sql/expression.py index e9786cbe1..b403ea88b 100644 --- a/lib/sqlalchemy/sql/expression.py +++ b/lib/sqlalchemy/sql/expression.py @@ -3687,7 +3687,6 @@ class Join(FromClause): self.onclause = onclause self.isouter = isouter - self.__folded_equivalents = None @property def description(self): @@ -3720,7 +3719,6 @@ class Join(FromClause): self.left = clone(self.left, **kw) self.right = clone(self.right, **kw) self.onclause = clone(self.onclause, **kw) - self.__folded_equivalents = None def get_children(self, **kwargs): return self.left, self.right, self.onclause @@ -3732,7 +3730,7 @@ class Join(FromClause): left_right = None return sqlutil.join_condition(left, right, a_subset=left_right) - def select(self, whereclause=None, fold_equivalents=False, **kwargs): + def select(self, whereclause=None, **kwargs): """Create a :class:`.Select` from this :class:`.Join`. The equivalent long-hand form, given a :class:`.Join` object @@ -3746,22 +3744,11 @@ class Join(FromClause): :param whereclause: the WHERE criterion that will be sent to the :func:`select()` function - :param fold_equivalents: based on the join criterion of this - :class:`.Join`, do not include - repeat column names in the column list of the resulting - select, for columns that are calculated to be "equivalent" - based on the join criterion of this :class:`.Join`. This will - recursively apply to any joins directly nested by this one - as well. - :param \**kwargs: all other kwargs are sent to the underlying :func:`select()` function. """ - if fold_equivalents: - collist = sqlutil.folded_equivalents(self) - else: - collist = [self.left, self.right] + collist = [self.left, self.right] return select(collist, whereclause, from_obj=[self], **kwargs) @@ -5149,6 +5136,37 @@ class Select(SelectBase): """ self.append_column(column) + def reduce_columns(self, only_synonyms=True): + """Return a new :func`.select` construct with redundantly + named, equivalently-valued columns removed from the columns clause. + + "Redundant" here means two columns where one refers to the + other either based on foreign key, or via a simple equality + comparison in the WHERE clause of the statement. The primary purpose + of this method is to automatically construct a select statement + with all uniquely-named columns, without the need to use table-qualified + labels as :meth:`.apply_labels` does. + + When columns are omitted based on foreign key, the referred-to + column is the one that's kept. When columns are omitted based on + WHERE eqivalence, the first column in the columns clause is the + one that's kept. + + :param only_synonyms: when True, limit the removal of columns + to those which have the same name as the equivalent. Otherwise, + all columns that are equivalent to another are removed. + + .. versionadded:: 0.8 + + """ + return self.with_only_columns( + sqlutil.reduce_columns( + self.inner_columns, + *(self._whereclause, ) + tuple(self._from_obj), + only_synonyms=only_synonyms + ) + ) + @_generative def with_only_columns(self, columns): """Return a new :func:`.select` construct with its columns |