Function lambda_stmt

lib/sqlalchemy/sql/lambdas.py:81–151

Produce a SQL statement that is cached as a lambda. The Python code object within the lambda is scanned for both Python literals that will become bound parameters as well as closure variables that refer to Core or ORM constructs that may vary. The lambda itself will be invoked onl

(
    lmb: _StmtLambdaType,
    enable_tracking: bool = True,
    track_closure_variables: bool = True,
    track_on: Optional[object] = None,
    global_track_bound_values: bool = True,
    track_bound_values: bool = True,
    lambda_cache: Optional[_LambdaCacheType] = None,
)

def lambda_stmt(
    lmb: _StmtLambdaType,
    enable_tracking: bool = True,
    track_closure_variables: bool = True,
    track_on: Optional[object] = None,
    global_track_bound_values: bool = True,
    track_bound_values: bool = True,
    lambda_cache: Optional[_LambdaCacheType] = None,
) -> StatementLambdaElement:
    """Produce a SQL statement that is cached as a lambda.

    The Python code object within the lambda is scanned for both Python
    literals that will become bound parameters as well as closure variables
    that refer to Core or ORM constructs that may vary.   The lambda itself
    will be invoked only once per particular set of constructs detected.

    E.g.::

        from sqlalchemy import lambda_stmt

        stmt = lambda_stmt(lambda: table.select())
        stmt += lambda s: s.where(table.c.id == 5)

        result = connection.execute(stmt)

    The object returned is an instance of :class:`_sql.StatementLambdaElement`.

    .. versionadded:: 1.4

    :param lmb: a Python function, typically a lambda, which takes no arguments
     and returns a SQL expression construct
    :param enable_tracking: when False, all scanning of the given lambda for
     changes in closure variables or bound parameters is disabled.  Use for
     a lambda that produces the identical results in all cases with no
     parameterization.
    :param track_closure_variables: when False, changes in closure variables
     within the lambda will not be scanned.   Use for a lambda where the
     state of its closure variables will never change the SQL structure
     returned by the lambda.
    :param track_bound_values: when False, bound parameter tracking will
     be disabled for the given lambda.  Use for a lambda that either does
     not produce any bound values, or where the initial bound values never
     change.
    :param global_track_bound_values: when False, bound parameter tracking
     will be disabled for the entire statement including additional links
     added via the :meth:`_sql.StatementLambdaElement.add_criteria` method.
    :param lambda_cache: a dictionary or other mapping-like object where
     information about the lambda's Python code as well as the tracked closure
     variables in the lambda itself will be stored.   Defaults
     to a global LRU cache.  This cache is independent of the "compiled_cache"
     used by the :class:`_engine.Connection` object.

    .. seealso::

        :ref:`engine_lambda_caching`


    """