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| author | Mike Bayer <mike_mp@zzzcomputing.com> | 2017-03-14 12:00:56 -0400 |
|---|---|---|
| committer | Mike Bayer <mike_mp@zzzcomputing.com> | 2017-03-14 17:01:07 -0400 |
| commit | f3b6f4f8da5223fae0a1dd948d4266b2e49e317c (patch) | |
| tree | 9cae69a0b1680161a5e6604371a17b5766c3dc34 /lib/sqlalchemy/engine/default.py | |
| parent | 596e322543df6ff380243c9cb0cf9997252329f6 (diff) | |
| download | sqlalchemy-f3b6f4f8da5223fae0a1dd948d4266b2e49e317c.tar.gz | |
Add "empty in" strategies; default to "static"
The longstanding behavior of the :meth:`.Operators.in_` and
:meth:`.Operators.not_in_` operators emitting a warning when
the right-hand condition is an empty sequence has been revised;
a new flag :paramref:`.create_engine.empty_in_strategy` allows an
empty "IN" expression to generate a simple boolean expression, or
to invoke the previous behavior of dis-equating the expression to
itself, with or without a warning. The default behavior is now
to emit the simple boolean expression, allowing an empty IN to
be evaulated without any performance penalty.
Change-Id: I65cc37f2d7cf65a59bf217136c42fee446929352
Fixes: #3907
Diffstat (limited to 'lib/sqlalchemy/engine/default.py')
| -rw-r--r-- | lib/sqlalchemy/engine/default.py | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/lib/sqlalchemy/engine/default.py b/lib/sqlalchemy/engine/default.py index 18c3276f8..b8c2d2845 100644 --- a/lib/sqlalchemy/engine/default.py +++ b/lib/sqlalchemy/engine/default.py @@ -178,6 +178,7 @@ class DefaultDialect(interfaces.Dialect): supports_right_nested_joins=None, case_sensitive=True, supports_native_boolean=None, + empty_in_strategy='static', label_length=None, **kwargs): if not getattr(self, 'ported_sqla_06', True): @@ -207,6 +208,17 @@ class DefaultDialect(interfaces.Dialect): self.supports_native_boolean = supports_native_boolean self.case_sensitive = case_sensitive + self.empty_in_strategy = empty_in_strategy + if empty_in_strategy == 'static': + self._use_static_in = True + elif empty_in_strategy in ('dynamic', 'dynamic_warn'): + self._use_static_in = False + self._warn_on_empty_in = empty_in_strategy == 'dynamic_warn' + else: + raise exc.ArgumentError( + "empty_in_strategy may be 'static', " + "'dynamic', or 'dynamic_warn'") + if label_length and label_length > self.max_identifier_length: raise exc.ArgumentError( "Label length of %d is greater than this dialect's" |