diff options
Diffstat (limited to 'lib/sqlalchemy/sql/selectable.py')
| -rw-r--r-- | lib/sqlalchemy/sql/selectable.py | 133 |
1 files changed, 86 insertions, 47 deletions
diff --git a/lib/sqlalchemy/sql/selectable.py b/lib/sqlalchemy/sql/selectable.py index 9e8cb3bc5..b4df87e54 100644 --- a/lib/sqlalchemy/sql/selectable.py +++ b/lib/sqlalchemy/sql/selectable.py @@ -746,6 +746,33 @@ class Join(FromClause): providing a "natural join". """ + constraints = cls._joincond_scan_left_right( + a, a_subset, b, consider_as_foreign_keys) + + if len(constraints) > 1: + cls._joincond_trim_constraints( + a, b, constraints, consider_as_foreign_keys) + + if len(constraints) == 0: + if isinstance(b, FromGrouping): + hint = " Perhaps you meant to convert the right side to a "\ + "subquery using alias()?" + else: + hint = "" + raise exc.NoForeignKeysError( + "Can't find any foreign key relationships " + "between '%s' and '%s'.%s" % + (a.description, b.description, hint)) + + crit = [(x == y) for x, y in list(constraints.values())[0]] + if len(crit) == 1: + return (crit[0]) + else: + return and_(*crit) + + @classmethod + def _joincond_scan_left_right( + cls, a, a_subset, b, consider_as_foreign_keys): constraints = collections.defaultdict(list) for left in (a_subset, a): @@ -780,57 +807,41 @@ class Join(FromClause): if nrte.table_name == b.name: raise else: - # this is totally covered. can't get - # coverage to mark it. continue if col is not None: constraints[fk.constraint].append((col, fk.parent)) if constraints: break + return constraints + @classmethod + def _joincond_trim_constraints( + cls, a, b, constraints, consider_as_foreign_keys): + # more than one constraint matched. narrow down the list + # to include just those FKCs that match exactly to + # "consider_as_foreign_keys". + if consider_as_foreign_keys: + for const in list(constraints): + if set(f.parent for f in const.elements) != set( + consider_as_foreign_keys): + del constraints[const] + + # if still multiple constraints, but + # they all refer to the exact same end result, use it. if len(constraints) > 1: - # more than one constraint matched. narrow down the list - # to include just those FKCs that match exactly to - # "consider_as_foreign_keys". - if consider_as_foreign_keys: - for const in list(constraints): - if set(f.parent for f in const.elements) != set( - consider_as_foreign_keys): - del constraints[const] - - # if still multiple constraints, but - # they all refer to the exact same end result, use it. - if len(constraints) > 1: - dedupe = set(tuple(crit) for crit in constraints.values()) - if len(dedupe) == 1: - key = list(constraints)[0] - constraints = {key: constraints[key]} - - if len(constraints) != 1: - raise exc.AmbiguousForeignKeysError( - "Can't determine join between '%s' and '%s'; " - "tables have more than one foreign key " - "constraint relationship between them. " - "Please specify the 'onclause' of this " - "join explicitly." % (a.description, b.description)) - - if len(constraints) == 0: - if isinstance(b, FromGrouping): - hint = " Perhaps you meant to convert the right side to a "\ - "subquery using alias()?" - else: - hint = "" - raise exc.NoForeignKeysError( - "Can't find any foreign key relationships " - "between '%s' and '%s'.%s" % - (a.description, b.description, hint)) - - crit = [(x == y) for x, y in list(constraints.values())[0]] - if len(crit) == 1: - return (crit[0]) - else: - return and_(*crit) + dedupe = set(tuple(crit) for crit in constraints.values()) + if len(dedupe) == 1: + key = list(constraints)[0] + constraints = {key: constraints[key]} + + if len(constraints) != 1: + raise exc.AmbiguousForeignKeysError( + "Can't determine join between '%s' and '%s'; " + "tables have more than one foreign key " + "constraint relationship between them. " + "Please specify the 'onclause' of this " + "join explicitly." % (a.description, b.description)) def select(self, whereclause=None, **kwargs): """Create a :class:`.Select` from this :class:`.Join`. @@ -2153,6 +2164,7 @@ class Select(HasPrefixes, GenerativeSelect): _prefixes = () _hints = util.immutabledict() + _statement_hints = () _distinct = False _from_cloned = None _correlate = () @@ -2525,10 +2537,30 @@ class Select(HasPrefixes, GenerativeSelect): return self._get_display_froms() + def with_statement_hint(self, text, dialect_name='*'): + """add a statement hint to this :class:`.Select`. + + This method is similar to :meth:`.Select.with_hint` except that + it does not require an individual table, and instead applies to the + statement as a whole. + + Hints here are specific to the backend database and may include + directives such as isolation levels, file directives, fetch directives, + etc. + + .. versionadded:: 1.0.0 + + .. seealso:: + + :meth:`.Select.with_hint` + + """ + return self.with_hint(None, text, dialect_name) + @_generative def with_hint(self, selectable, text, dialect_name='*'): - """Add an indexing hint for the given selectable to this - :class:`.Select`. + """Add an indexing or other executional context hint for the given + selectable to this :class:`.Select`. The text of the hint is rendered in the appropriate location for the database backend in use, relative @@ -2555,9 +2587,16 @@ class Select(HasPrefixes, GenerativeSelect): mytable, "+ index(%(name)s ix_mytable)", 'oracle').\\ with_hint(mytable, "WITH INDEX ix_mytable", 'sybase') + .. seealso:: + + :meth:`.Select.with_statement_hint` + """ - self._hints = self._hints.union( - {(selectable, dialect_name): text}) + if selectable is None: + self._statement_hints += ((dialect_name, text), ) + else: + self._hints = self._hints.union( + {(selectable, dialect_name): text}) @property def type(self): |