RealTimeSearchIndex and m2m_changed signal

[bwilliamson]

Hi,
We are using the RealTimeSearchIndex and notice that it's indexing
everything but m2m fields. Are there any plans to support the new
m2m_changed signal to index m2m fields via the RealTimeSearchIndex?

Brian

[Jeremy Bowers]

We had this problem too, and hacked together a clumsy scheme to
reindex on a post_save signal. It's running the index command twice,
but it's a start.

+1 for native solution to this.

[Daniel Lindsley]

Brian,

Many to many is not planned, simply because search engines are not
relational, so primary keys don't mean much. It's far better to
denormalize related data onto the parent (usually in the ``text``
template) or to use custom ``prepare_FOO`` methods in conjunction with
a ``MultiValueField`` to grab the primary keys/slugs/names/whatever
makes sense for your related data. The archives of this mailing list
has many examples (search for "tags").

As for Jeremy's solution & the m2m_changed signal, the problem lies
in backward-compatibility, since Django 1.0 & 1.1 don't have it (both
of which Haystack supports). It'll be a consideration going forward
but I don't feel comfortable building it in at the moment. And given
that it's simply a subclass of ``RealTimeSearchIndex`` with a couple
extra lines of code, it should be doable for your needs.

Finally, adding an issue to GitHub would help me remember to
implement it in the future
(http://github.com/toastdriven/django-haystack/issues).

Daniel

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[Danny Adair]

Today I was going to ask the list about that same thing. :-)

Also using RealTimeSearchIndex, I've got calculated values hanging off
m2m and foreignkey relationships which need to be updated when the
other object changes. (for example an account balance which is
calculated from credit/debit entries having the account as their
foreignkey - need to update the balance when an entry is
added/removed/changed)

Can I hook into the signal and update manually?

Cheers,
Danny

[Daniel Lindsley]

Danny,

Hooking in to related models is usually as simple as overriding
``_setup_save``
(http://github.com/toastdriven/django-haystack/blob/master/haystack/indexes.py#L211-215)
in your ``SearchIndex`` subclass. Something like:

====
from django.db.models import signals
from haystack import indexes
from haystack import site
from myapp.models import MainModel, M2MModel

class MySearchIndex(indexes.RealTimeSearchIndex):
# ... Fields here...
# Then...

def _setup_save(self, model):
super(MySearchIndex, self)._setup_save(model)
signals.post_save.connect(self.update_object, sender=M2MModel)

====

Hope that helps.

Daniel

[Danny Adair]

Thanks Daniel,

On Tue, Aug 10, 2010 at 17:17, Daniel Lindsley <pola...@gmail.com> wrote:
>[...]

> class MySearchIndex(indexes.RealTimeSearchIndex):
>    # ... Fields here...
>    # Then...
>
>    def _setup_save(self, model):
>        super(MySearchIndex, self)._setup_save(model)
>        signals.post_save.connect(self.update_object, sender=M2MModel)

I've tried that and it seems as if the fields are attempted to be
looked up in the other instance (it's got a foreign key to the main
model, not m2m).

Django Version: 1.2.1 SVN-13303
Exception Type: SearchFieldError
Exception Value:

The model '<RelatedModel: MainModel #13786 Related Model>' does not
have a model_attr 'my_main_model_attr'.

Exception Location:
/home/danny/environments/my.env/lib/python2.6/site-packages/haystack/fields.py
in prepare, line 69
Python Executable: /home/danny/environments/my.env/bin/python2.6
Python Version: 2.6.5

I get this when saving the RelatedModel instance, when I expected
"my_main_model_attr" to be looked up for index update from the main
model?

Cheers,
Danny

[Danny Adair]

Just in case someone else gets bitten by this:
I was naming the search index fields the same as the model field they
were indexing.
myfield = CharField(model_attr='myfield')

However what wasn't so clever was to do the same with related lookups:
relatedfield__otherattr = CharField(model_attr='relatedfield__otherattr')

Don't use double underscores :-)

Cheers,
Danny

--
Kind regards,

Danny W. Adair
Director
Unfold Limited
New Zealand

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