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from django.db import models
from haystack.exceptions import NotHandled
class BaseSignalProcessor:
"""
A convenient way to attach Haystack to Django's signals & cause things to
index.
By default, does nothing with signals but provides underlying functionality.
"""
def __init__(self, connections, connection_router):
self.connections = connections
self.connection_router = connection_router
self.setup()
def setup(self):
"""
A hook for setting up anything necessary for
``handle_save/handle_delete`` to be executed.
Default behavior is to do nothing (``pass``).
"""
# Do nothing.
pass
def teardown(self):
"""
A hook for tearing down anything necessary for
``handle_save/handle_delete`` to no longer be executed.
Default behavior is to do nothing (``pass``).
"""
# Do nothing.
pass
def handle_save(self, sender, instance, **kwargs):
"""
Given an individual model instance, determine which backends the
update should be sent to & update the object on those backends.
"""
using_backends = self.connection_router.for_write(instance=instance)
for using in using_backends:
try:
index = self.connections[using].get_unified_index().get_index(sender)
index.update_object(instance, using=using)
except NotHandled:
# TODO: Maybe log it or let the exception bubble?
pass
def handle_delete(self, sender, instance, **kwargs):
"""
Given an individual model instance, determine which backends the
delete should be sent to & delete the object on those backends.
"""
using_backends = self.connection_router.for_write(instance=instance)
for using in using_backends:
try:
index = self.connections[using].get_unified_index().get_index(sender)
index.remove_object(instance, using=using)
except NotHandled:
# TODO: Maybe log it or let the exception bubble?
pass
class RealtimeSignalProcessor(BaseSignalProcessor):
"""
Allows for observing when saves/deletes fire & automatically updates the
search engine appropriately.
"""
def setup(self):
# Naive (listen to all model saves).
models.signals.post_save.connect(self.handle_save)
models.signals.post_delete.connect(self.handle_delete)
# Efficient would be going through all backends & collecting all models
# being used, then hooking up signals only for those.
def teardown(self):
# Naive (listen to all model saves).
models.signals.post_save.disconnect(self.handle_save)
models.signals.post_delete.disconnect(self.handle_delete)
# Efficient would be going through all backends & collecting all models
# being used, then disconnecting signals only for those.
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