diff options
Diffstat (limited to 'lib/sqlalchemy/sql/expression.py')
| -rw-r--r-- | lib/sqlalchemy/sql/expression.py | 30 |
1 files changed, 29 insertions, 1 deletions
diff --git a/lib/sqlalchemy/sql/expression.py b/lib/sqlalchemy/sql/expression.py index 1e02ba96a..3aaa06fd6 100644 --- a/lib/sqlalchemy/sql/expression.py +++ b/lib/sqlalchemy/sql/expression.py @@ -3557,6 +3557,7 @@ class Select(_SelectBaseMixin, FromClause): __visit_name__ = 'select' _prefixes = () + _hints = util.frozendict() def __init__(self, columns, @@ -3659,7 +3660,34 @@ class Select(_SelectBaseMixin, FromClause): """Return the displayed list of FromClause elements.""" return self._get_display_froms() - + + @_generative + def with_hint(self, selectable, text, dialect_name=None): + """Add an indexing hint for the given selectable to this :class:`Select`. + + The text of the hint is written specific to a specific backend, and + typically uses Python string substitution syntax to render the name + of the table or alias, such as for Oracle:: + + select([mytable]).with_hint(mytable, "+ index(%(name)s ix_mytable)") + + Would render SQL as:: + + select /*+ index(mytable ix_mytable) */ ... from mytable + + The ``dialect_name`` option will limit the rendering of a particular hint + to a particular backend. Such as, to add hints for both Oracle and + Sybase simultaneously:: + + select([mytable]).\ + with_hint(mytable, "+ index(%(name)s ix_mytable)", 'oracle').\ + with_hint(mytable, "WITH INDEX ix_mytable", 'sybase') + + """ + if not dialect_name: + dialect_name = '*' + self._hints = self._hints.union({(selectable, dialect_name):text}) + @property def type(self): raise exc.InvalidRequestError("Select objects don't have a type. " |