Source code for deephaven.liveness_scope

# Copyright (c) 2016-2022 Deephaven Data Labs and Patent Pending

"""This module gives the users a finer degree of control over when to clean up unreferenced nodes in the query update
graph instead of solely relying on garbage collection."""
import contextlib

import jpy
from deephaven._wrapper import JObjectWrapper

_JLivenessScopeStack = jpy.get_type("io.deephaven.engine.liveness.LivenessScopeStack")
_JLivenessScope = jpy.get_type("io.deephaven.engine.liveness.LivenessScope")

[docs]class LivenessScope(JObjectWrapper): """A LivenessScope automatically manages reference counting of tables and other query resources that are created in it. It should not be instantiated directly but rather through the 'liveness_scope' context manager. """ j_object_type = _JLivenessScope def __init__(self, j_scope: jpy.JType): self.j_scope = j_scope @property def j_object(self) -> jpy.JType: return self.j_scope
[docs] def preserve(self, wrapper: JObjectWrapper) -> None: """Preserves a query graph node (usually a Table) to keep it live for the outer scope.""" _JLivenessScopeStack.pop(self.j_scope) _JLivenessScopeStack.peek().manage(wrapper.j_object) _JLivenessScopeStack.push(self.j_scope)
[docs]@contextlib.contextmanager def liveness_scope() -> LivenessScope: """Creates a LivenessScope for running a block of code and releases all the query graph resources upon exit. It can be used in a nested way. Returns: a LivenessScope """ j_scope = _JLivenessScope() _JLivenessScopeStack.push(j_scope) try: yield LivenessScope(j_scope=j_scope) finally: _JLivenessScopeStack.pop(j_scope) j_scope.release()