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Searching for products

This section explains Spree’s support for product search and selection.
After reading it you should know:

  • how the Searcher API works
  • how to install and configure a searcher instance
  • how to configure and use faceted search

This guide is aimed at developers.

endprologue.

Overview

Searching for products is a key operation for commerce sites, where we need both speed and flexibility.
Spree supports this by providing an API that allows plug-in and configuration of a variety of specialized,
high-performance search platforms. Furthermore, the core team maintains instances of this API for a few
of the current top platforms, such as Solr and
Sphinx.

The primary use of these platforms in Spree is to provide flexible full-text searching of product
details. Spree submits a query and then paginates the result.

Depending on the exact platform in use, Spree may also advise on searches with alternative spellings,
or support refinement or drilling down in the search result via
facets.

Searcher API

Configuration

You can set the current search implementation by assigning a suitable object to
Spree::Config.searcher_class.
If it is not set, the searcher defaults to an instance of the base implementation.

Integration with Spree

The primary modification is to override the named scope for general keyword lookup.
Thus Product.keywords(“foo”) will use the configured search implementation, and return
a new scope which limits its result to products which match the query.

One standard use of the keywords scope is to implement the default Spree search box.
The method retrieve_products (now in lib/spree/search.rb) handles display of product
lists based on a mix of keywords, taxon selections, product group(s) and facets.
It uses the searcher API to set up searches, then the actual search occurs via (indirect)
calls to the keywords scope, e.g. as a clause in a product group or in response to
presence of a keyword parameter in the query.
Note that retrieve_products is used to generate listings in the Product and Taxon
controllers: you’ll probably need to use it if generating similar listings.

Standard interface

See the existing search implementations for concrete examples, e.g.
the base implementation
or spree-solr-search.

new

The API is managed through a class, so if you are replacing the default instance, you need to create
a new instance of your search class.

get_products_conditions_for(query)

This is the main call. Its purpose is to format the query appropriately and retrieve information from
the search platform, then return it in the form of a named scope.
Typically, you will retrieve a list of product ids i1, i2, …
from the platform and produce the result {:conditions => “products.id IN (i1, i2, …)”} (though
you are free to include other scope elements too).

The format of input query is not fixed, though you should expect to be able to handle a string or
a list of strings.

prepare(params)

This call is intended to set up the context for complex calls to the search platform, e.g. to allow
for pagination or faceting. It is normally called in retrieve_products, with (some of) the parameters
from a product display query.

IMPORTANT: it seems that prepare() should act more like a wrapper around restricted calls, and clear the (modified) properties after the important call – else subsequent calls WILL be affected by old (or a previous request’s) data.

manage_pagination

This should return true if the search platform can manage its own pagination of results.

method_missing

The base implemementation defines this to provide easy access to the properties stored with prepare or
added during get_products_conditions_for, such as the pagination flag above (which is nil/absent for the
base implementation).

The base implementation

The most notable point is the implementation of get_products_conditions_for: it just uses a named
scope (Product.name_or_description_like_any, provided by SearchLogic) to search for a substring in
the name or description fields.

The Solr instance

Solr is an industrial-scale search platform, with many features and
settings.

Roman Smirnov has produced an extension spree-solr-search
for a direct connection into Spree. It contains a searcher instance, and configures Solr for
indexing on certain attributes of the Product model. There is also code for declaring facets
and for enabling drill-down by those facets (with the _facets partial).
The acts_as_solr plugin is used to handle low-level communication.

Installation

1. script/extension install git://github.com/romul/spree-solr-search.git to install the extension
1. Copy solr_search/config/solr.yml to RAILS_ROOT/config/solr.yml, and edit if you need to change host names or port numbers.
1. Check that you have all required gems/plugins, e.g. using rake gems:install

You also need a running Solr server (or several, if you want to isolate development/testing work
from production data). There are several options for this. For development and testing, we recommend
Diego Carrion’s jetty-solr project (NB he also wrote the
acts-as-solr-reloaded plugin). Once you have cloned the project, just run ./start in the
base directory to run a development server on port 8982. Other options and configurations are given
in the documentation. You can also start the server from your rails project via
rake solr:start SOLR_PATH=XYZ (replacing XYZ with the base of your jetty-solr installation),
and stop it with rake solr:stop.

Jetty-solr can be used for production use too, though the
Solr documentation advises exploring other options and experimenting with the
various configuration parameters to get best performance in high-traffic scenarios.

How Solr is tied to Spree

The first step is to declare which ‘attributes’ of which models should be indexed, and of these, which
should be treated as facets. The attributes can be conventional model attributes, or the names
of methods which generate appropriate result strings. If non-string values are needed, then indicate
the type as done for :price.

Product.class_eval do
acts_as_solr :fields => [:name, :description, :is_active, {:price => :float}, :taxon_ids,
:price_range, :taxon_names, :brand_property, :color_option, :size_option],
:facets => [:price_range, :taxon_names, :brand_property, :color_option, :size_option]

The second step is to format the query in get_product_conditions_for. The current code sets the
appropriate sort order and injects taxon constraints, if relevant. In particular, a request within
a particular taxon is expanded to include all of the taxon’s descendents. The final step is to
set up the pagination.

NOTE: Some of the query parameters are derived from the information registered in the prepare() call.

Indexing and reindexing

Creating the index and updating it is done with the same command: rake solr:reindex

The underlying plugin recognises several options, e.g. BATCH=500 to submit new products to the
Solr server in batches of 500 (the default is currently 300).

Solr tuning and configuration

There are many settings to control the behaviour of Solr instances. See the documentation and
config files in Jetty-solr for basic information, or the official Solr documentation.

Facet support

Facets allow large search results to be filtered according to properties a user may be interested in.
For example, we can search for rails and then select the clothing taxon(s) and a certain price range
to end up with a more manageable number of products.

Faceting with Solr

Solr directly supports faceting, and can index declared facets alongside the conventional data. You can
include facet constraints in a Solr query, and can obtain information about the available facets
that can be used to drill down in a given query.

Smirnov’s extension makes it easy to incorporate facet
functionality into Spree. By default it generates facets for the following:

  • product brand (via a “brand” property)
  • colors of a product’s variants (via the variant options)
  • sizes of a product’s variants (via the variant options)
  • ‘primary’ taxons – the taxons to which the product is explicitly assigned (not the implicit descendants)
  • price range, in bands of 0-25, 25-50, 50-100,100-200,200 and over.

The extension also includes a basic partial for displaying and requesting facet results, which you can
include or replace in your own site theme.

WARNING: The price range code does not work at the moment.

NOTE: The description text of the price bands will need modification if used in non-US locales. The text is held in Spree::Config[:product_price_ranges].

Declaration of facets

Facet declaration requires two steps. First, to declare the facet as an indexable field of the
product, and second, to declare that the field is a facet.

Product.class_eval do
acts_as_solr :fields => [:name, :description, :is_active, {:price => :float}, :taxon_ids,
:price_range, :taxon_names, :brand_property, :color_option, :size_option],
:facets => [:price_range, :taxon_names, :brand_property, :color_option, :size_option]

Field names should be methods of the object being indexed. For the default facets, we have methods
which return a product’s brand (as a string), or return the colors of any variants (as a list of strings).
If you need other return types, they should be declared as shown for :price.

To add a new facet based on some other property or option value, you should just provide a method
which generates the relevant information and include it in the lists above. You could also override
the provided methods if you need more specialized treatment of brand etc.

If you have changed or added to the facets, then you will need to reindex the
database
.

Query processing

There are several options to include in the Solr query when using facets, including which facet (if any)
is being requested and limits on result size. The only part a developer may usually want to change is
the list of facet results being requested: this is currently set near the top of file
solr_search/lib/spree/search/solr.rb.

Solr returns the requested facet information as a nested hash, and the Solr extension converts this to a
list of Spree::Search::Facet values, each containing a facet name and a list of facet options. Each
Spree::Search::FacetOption value contains an option string (eg a specific color) and the count of
matched products. This information can be used to generate links.

Display and selection of options

The partial app/views/products/_facets.html.erb provides a basic interface to the facets in a format
suitable for inclusion in a sidebar, using the list of Spree::Search::Facet values returned by the
most recent query. Each non-empty facet is mapped to a title and unordered list of links.
A helper function link_to_facet will generate links which add a facet option to the currently
active constraints (and in turn, this can be decoded by the solr query generation).

Note that you can pick several options from certain facets (based on variants or taxons), eg you can
select color ‘Red’ and on the resulting page, select ‘Green’. The effect is to return only the products
whose color values include both red and green, or more precisely, only the products which have
variants whose colour option is either red or green.

Technically speaking, this means that the standard behaviour with Solr is to produce an intersection
of constraints, not a union. So if you want to allow display of products whose brand is A or B,
then some custom programming will be required.

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