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Search Engine

Mezzanine comes with a built-in search engine that allows site visitors to search across different types of content. The following section describes how to programmatically interact with the search engine, how to customize the way the search engine accesses different types of content, and how search queries are broken down and used to query models for results.

Search API

The main search API is provided by mezzanine.core.managers.SearchableManager. This is a Django model manager that provides a custom search method. Adding search functionality to any model is as simple as using the SearchableManager as a manager for your model.

Note

By following the previous example outlined in :ref:`creating-custom-content-types` no extra work is required to have your custom content included in search queries, as the default search functionality in Mezzanine (defined in mezzanine.core.views.search) automatically covers any models that inherit from mezzanine.pages.models.Page or mezzanine.core.models.Displayable.

In its most simple form, the search method takes a single string argument containing a search query and returns a Django queryset representing the results. For example, to search for all pages using the term plans prices projects:

from mezzanine.pages.models import Page

results = Page.objects.search("plans prices projects")

It's also possible to explicitly control which fields will be used for the search. For example to search Page.title and Page.content only:

from mezzanine.pages.models import Page

query = "plans prices projects"
search_fields = ("title", "content")
results = Page.objects.search(query, search_fields=search_fields)

If search_fields is not provided in the call to search, the fields used will be the default fields specified for the model. These are specified by providing a search_fields attribute on any model that uses the SearchableManager. For example, if we wanted to add search capabilities to our GalleryImage model from the previous example in :ref:`creating-custom-content-types`:

from django.db import models
from mezzanine.pages.models import Page
from mezzanine.core.managers import SearchableManager

class Gallery(Page):
    pass

# Added the title and description fields here for the search example.
class GalleryImage(models.Model):
    gallery = models.ForeignKey("Gallery")
    title = models.CharField("Title", max_length=100)
    description = models.CharField("Description", max_length=1000)
    image = models.ImageField(upload_to="galleries")

    objects = SearchableManager()
    search_fields = ("title", "description")

If search_fields are not specified using any of the approaches above, then all CharField and TextField fields defined on the model are used.

Ordering Results

By default, results are ordered by the number of matches found within the fields searched. It is possible to control the relative weight of a match found within one field over a match found in another field. Given the first example of searching Page instances, you might decide that a match within the title field is worth 5 times as much as a match in the description field. These relative weights can be defined in the same fashion as outlined above for defining the fields to be used in a search by using a slightly different format for the search_fields argument:

from mezzanine.pages.models import Page

query = "plans prices projects"
search_fields = {"title": 5, "content": 1}
results = Page.objects.search(query, search_fields=search_fields)

As shown, a dictionary or mapping sequence can be used to associate weights to fields in any of the cases described above where search_fields can be defined.

Searching Heterogeneous Models

So far we've looked at how to search across a single model, but what if we want to search across different types of models at once? This is possible through the use of abstract models. SearchableManager is designed so that if it is accessed directly through an abstract model, it will search across every model that subclasses the abstract model. This makes it possible to group together different types of models for the purpose of combined search. Continuing on from our GalleryImage example, suppose we also have a Document model containing files uploaded and that we wanted a combined search across these models which could both be conceptually defined as assets. We would then go ahead and create an abstract model called Asset for the sake of grouping these together for search:

class Asset(models.Model):
    title = models.CharField("Title", max_length=100)
    description = models.CharField("Title", max_length=1000)

    objects = SearchableManager()
    search_fields = ("title", "description")

    class Meta:
        abstract = True

class GalleryImage(Asset):
    gallery = models.ForeignKey("Gallery")
    image = models.ImageField(upload_to="galleries")

class Document(Asset):
    image = models.FileField(upload_to="documents")

By accessing SearchableManager directly via the Asset abstract model we can search across the GalleryImage and Document models at once:

>>> Asset.objects.search("My")
[<GalleryImage: My Image 1>, <Document: My Doc>, <GalleryImage: My Image 2>]

Note

It was mentioned earlier that the search method returns a Django queryset meaning that you can then chain together further queryset methods onto the result. However when searching across heterogeneous models via an abstract model, this is not the case and the result is a list of model instances.

Query Behaviour

When a call to SearchableManager.search is performed, the query entered is processed through several steps until it is translated into a Django queryset. By default the query is broken up into keywords, so the query plans prices projects would return results that contain any of the words plans or prices or projects.

The query can contain several special operators which allow for this behaviour to be controlled further. Quotes around exact phrases will ensure that the phrase is searched for specifically, for example the query "plans prices" projects will return results matching the exact phrase plans prices or the word projects, in contrast to the previous example.

You can also prefix both words and phrases with + or - symbols. The + symbol will ensure the word or phrase is contained in all results, and the - symbol will ensure that no results will be returned containing the word or phrase. For example the query +"plans prices" -projects would return results that must contain the phrase plans prices and must not contain the word projects.

Once the query has been parsed into words and phrases to be included or excluded, a second step is performed where the query is stripped of common words know as stop words. These are common words such as and, the or like that are generally not meaningful and cause irrelevant results to be returned. The list of stop words is stored in the setting STOP_WORDS as described in the :doc:`configuration` section.

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