Highlight search terms on a Django/PostgreSQL search results page

Question

How can I create a search results page in Django 1.11, using PostgreSQL full text search, where the terms searched for are highlighted?

Answer 1

Even though Django doesn't support ts_headline feature from postgresql, You can manually apply it as a Function on a QuerySet to annotate:

---

We need additional function to operate with django ORM. Here is a sample for ts_headline. [original_source for this sample function is linked here]

Headline function sample:

from django.db import models
from django.contrib.postgres.search import Value, Func


class Headline(Func):
    function = 'ts_headline'

    def __init__(self, field, query, config=None, options=None, **extra):
        expressions = [field, query]
        if config:
            expressions.insert(0, Value(config))
        if options:
            expressions.append(Value(options))
        extra.setdefault('output_field', models.TextField())
        super().__init__(*expressions, **extra)

Using the above function you can use it on a QuerySet to annotate

Example Model Definition

class Video(Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    title = models.CharField(max_length=128, verbose_name="Title")

---

Steps for getting highlighted search results on model title

1. Filter and get the QuerySet needed to annotated
2. Annotate using Headline function
3. Get Values of your document

---

Filtering Objects

Video.objects.filter(filter_query)

filter_query is a Q() over title filter_query = Q(title__contains=term)

---

Annotation with Headline data

Video.objects.filter(filter_query).annotate(title_highlight=Headline(F('title'), text_search_query))

ts_headline directly take the input from the document rather than from ts_vector, So we have to pass the information about which field it should access and what SearchQuery it should perform on it.

text_Search_query is SearchQuery Object with same input as the filter_query text_search_query = SearchQuery(term)

Now after annotation, this queryset with include a extra field in all objects called title_highlight which would contain the result you wanted like:

these <b>loans</b> not being repaired

---

Get the values from the annotation field

using values_list over the QuerySet you can get the values from these annotated fields.

final code:

Video.objects.filter(filter_query).annotate(title_highlight=Headline(F('title'), text_search_query)).values_from('title','title_highlight')