diff options
Diffstat (limited to 'lib/sqlalchemy/sql')
| -rw-r--r-- | lib/sqlalchemy/sql/expression.py | 38 |
1 files changed, 33 insertions, 5 deletions
diff --git a/lib/sqlalchemy/sql/expression.py b/lib/sqlalchemy/sql/expression.py index 7204e2956..7eeff0660 100644 --- a/lib/sqlalchemy/sql/expression.py +++ b/lib/sqlalchemy/sql/expression.py @@ -33,6 +33,7 @@ from sqlalchemy import util, exc from sqlalchemy.sql import operators from sqlalchemy.sql.visitors import Visitable, cloned_traverse from sqlalchemy import types as sqltypes +import operator functions, schema, sql_util = None, None, None DefaultDialect, ClauseAdapter, Annotated = None, None, None @@ -1840,9 +1841,32 @@ class FromClause(Selectable): for c in cols: i = c.proxy_set.intersection(target_set) if i and \ - (not require_embedded or c.proxy_set.issuperset(target_set)) and \ - (intersect is None or len(i) > len(intersect)): - col, intersect = c, i + (not require_embedded or c.proxy_set.issuperset(target_set)): + + if col is None: + # no corresponding column yet, pick this one. + col, intersect = c, i + elif len(i) > len(intersect): + # 'c' has a larger field of correspondence than 'col'. + # i.e. selectable.c.a1_x->a1.c.x->table.c.x matches a1.c.x->table.c.x better than + # selectable.c.x->table.c.x does. + col, intersect = c, i + elif i == intersect: + # they have the same field of correspondence. + # see which proxy_set has fewer columns in it, which indicates a + # closer relationship with the root column. Also take into account the + # "weight" attribute which CompoundSelect() uses to give higher precedence to + # columns based on vertical position in the compound statement, and discard columns + # that have no reference to the target column (also occurs with CompoundSelect) + col_distance = util.reduce(operator.add, + [sc._annotations.get('weight', 1) for sc in col.proxy_set if sc.shares_lineage(column)] + ) + c_distance = util.reduce(operator.add, + [sc._annotations.get('weight', 1) for sc in c.proxy_set if sc.shares_lineage(column)] + ) + if \ + c_distance < col_distance: + col, intersect = c, i return col @property @@ -3097,8 +3121,12 @@ class CompoundSelect(_SelectBaseMixin, FromClause): def _populate_column_collection(self): for cols in zip(*[s.c for s in self.selects]): proxy = cols[0]._make_proxy(self, name=self.use_labels and cols[0]._label or None) - proxy.proxies = cols - + + # place a 'weight' annotation corresponding to how low in the list of select()s + # the column occurs, so that the corresponding_column() operation + # can resolve conflicts + proxy.proxies = [c._annotate({'weight':i + 1}) for i, c in enumerate(cols)] + def _copy_internals(self, clone=_clone): self._reset_exported() self.selects = [clone(s) for s in self.selects] |