Implementing a basic search for my website

[Carlo Ascani]

Hi all,

I am just trying to add a search funcionality to my frontend.

I know it is a huge topic, so sorry my n00bih questions.

I have a model A

class A(models.Model):

    roles = models.ManyToManyField(B)

    location = models.ForeignKey(C)

    ...

These 2 fields are the only fields I care about

when searching, so I would say I need a very

specific field based search funcionality.

I wrote this view to handle it

class ASearch(ListView):

    model = A

    template_name = 'search_result.html'

    def get_context_data(self, **kwargs):

        context = super(A, self).get_context_data(**kwargs)

        results = A.objects.all()

        query = self.request.GET.get('q')

        if query:

            query_list = query.split()

            results = results.filter(

                reduce(operator.or_, (

                    Q(roles__name__icontains=q)

                        for q in query_list)) |

                reduce(operator.or_, (

                    Q(location__name__iexact=q)

                        for q in query_list))

                )

        context.update({

            'results': results

        })

        return context

This is quite working. I mean, results are fine.

But the problem is that I would like that searches

who covers *all* conditions to come first.

For example, let's say I search for 'MyRole MyLocation'

the results I get are all the As for MyRole and all the

As for MyLocation, mixed.

I would like that As with MyRole AND MyLocation to show

up first.

I hope I was clear enough, but I doubt it.

Thank you in advance

[ludovic coues]

You can split your query set in two. First search elements with both elements then elements with only one.

Obviously, that's two request, so there might be better way to handle the problem.

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[Melvyn Sopacua]

Hi Carlo,

 

On Monday 20 February 2017 07:33:08 Carlo Ascani wrote:

 

> class ASearch(ListView):

> model = A

> template_name = 'search_result.html'

>

> def get_context_data(self, **kwargs):

> context = super(A, self).get_context_data(**kwargs)

> results = A.objects.all()

> query = self.request.GET.get('q')

>

> if query:

> query_list = query.split()

>

> results = results.filter(

> reduce(operator.or_, (

> Q(roles__name__icontains=q)

> for q in query_list)) |

> reduce(operator.or_, (

> Q(location__name__iexact=q)

> for q in query_list))

> )

>

> context.update({

> 'results': results

> })

> return context

 

I think in itself your logic is already becoming complex. With the added condition, which is in essence "scoring the results" a simple ordering can't be done here. It really is worth looking into Full Text Search options of your database engine or use an external service for it.

 

If you feel like doing it this way anyway, I would do the reordering in python - databases have invented FTS for this for a good reason: reordering a result set almost always involves doing temporary tables, especially if the ordering conditions are not a table field, but a condition of the results.

 

The good thing is that the sorting is in fact a split: if both have a match, move to top, else move to bottom, so a classic Tail Queue will work.

 

And that also makes using Ludovic's suggestion viable: use 2 queries. One anding the 2 conditions, which should be fast and the second somewhat more complex: where NOT the anded condition and the OR condition.

 

Which to pick, is really a matter of performance: which method does best under pressure and what resource can you scale cheaper / faster?

--

Melvyn Sopacua

[Shawn Milochik]

If you want a pre-rolled solution, just use Django-haystack. It'll do exactly what you want.

If you want to create your own to avoid the dependency on additional libraries and backend (you'll need something like Elasticsearch), that's easy also. Let me know if you do. I have some sample code lying around and will dig it up and document it a bit if you're interested in implementing it. You'll still need to have to store your own indexed data in some kind of backend, but you can use whatever you like.

[Carlo Ascani]

Thank you for all the answers!

Given that I am implementing this for a demo purpose, I do not care about performances.

I think I am going to do the 2 queries approach for the demo, then I would use a FTS engine in the future.

Thanks a lot

Carlo