diff options
Diffstat (limited to 'lib/sqlalchemy/sql/selectable.py')
| -rw-r--r-- | lib/sqlalchemy/sql/selectable.py | 27 |
1 files changed, 15 insertions, 12 deletions
diff --git a/lib/sqlalchemy/sql/selectable.py b/lib/sqlalchemy/sql/selectable.py index 0bb590bd0..c554429be 100644 --- a/lib/sqlalchemy/sql/selectable.py +++ b/lib/sqlalchemy/sql/selectable.py @@ -183,7 +183,7 @@ def lateral(selectable, name=None): return selectable.lateral(name=name) -def tablesample(selectable, arg, name=None, method=None, seed=None): +def tablesample(selectable, sampling, name=None, seed=None): """Return a :class:`.TableSample` object. :class:`.TableSample` is an :class:`.Alias` subclass that represents @@ -193,15 +193,13 @@ def tablesample(selectable, arg, name=None, method=None, seed=None): percentage of rows from a table. It supports multiple sampling methods, most commonly BERNOULLI and SYSTEM. - :param arg: a ``float`` percentage between 0 and 100. - - :param method: string name of the method to use. - Commonly accepted methods are ``"BERNOULLI"`` and ``"SYSTEM"``. + :param sampling: a ``float`` percentage between 0 and 100 or + :class:`.functions.Function`. :param seed: any real-valued SQL expression. """ - return selectable.sample(arg, name=name, method=method, seed=seed) + return selectable.sample(sampling, name=name, seed=seed) class Selectable(ClauseElement): @@ -471,14 +469,14 @@ class FromClause(Selectable): """ return Lateral(self, name) - def sample(self, arg, name=None, method=None, seed=None): + def sample(self, sampling, name=None, seed=None): """Return a TABLESAMPLE alias of this :class:`.FromClause`. The return value is the :class:`.TableSample` construct also provided by the top-level :func:`~.expression.tablesample` function. """ - return TableSample(self, arg, name, method, seed) + return TableSample(self, sampling, name, seed) def is_derived_from(self, fromclause): """Return True if this FromClause is 'derived' from the given @@ -1285,15 +1283,20 @@ class TableSample(Alias): __visit_name__ = 'tablesample' - def __init__(self, selectable, arg, + def __init__(self, selectable, sampling, name=None, - method=None, seed=None): - self.arg = arg - self.method = method or 'SYSTEM' + self.sampling = sampling self.seed = seed super(TableSample, self).__init__(selectable, name=name) + @util.dependencies("sqlalchemy.sql.functions") + def _get_method(self, functions): + if isinstance(self.sampling, functions.Function): + return self.sampling + else: + return functions.func.system(self.sampling) + class CTE(Generative, HasSuffixes, Alias): """Represent a Common Table Expression. |