AttrSearchable

AttrSearchable extends your ActiveRecord models to support fulltext search engine like queries via simple query strings and hash-based queries. Assume you have a Book model having various attributes like title, author, stock, price, available. Using AttrSearchable you can perform:

Book.search("Joanne Rowling Harry Potter")
Book.search("author: Rowling title:'Harry Potter'")
Book.search("price > 10 AND price < 20 -stock:0 (Potter OR Rowling)")
# ...

Thus, you can hand out a search query string to your models and you, your app's admins and/or users will get powerful query features without the need for integrating additional third party search servers, since AttrSearchable can use fulltext index capabilities of your RDBMS in a database agnostic way (currently MySQL and PostgreSQL fulltext indices are supported) and optimizes the queries to make optimal use of them. Read more below.

Complex hash-based queries are supported as well:

Book.search(:author => "Rowling", :title => "Harry Potter")
Book.search(:or => [{:author => "Rowling"}, {:author => "Tolkien"}])
Book.search(:and => [{:price => {:gt => 10}}, {:not => {:stock => 0}}, :or => [{:title => "Potter"}, {:author => "Rowling"}]])
Book.search(:or => [{:query => "Rowling -Potter"}, {:query => "Tolkien -Rings"}])
# ...

Installation

For Rails/ActiveRecord 3 (or 4), add this line to your application's Gemfile:

gem 'attr_searchable'

And then execute:

$ bundle

Or install it yourself as:

$ gem install attr_searchable

Usage

To enable AttrSearchable for a model, include AttrSearchable and specify the attributes you want to expose to search queries:

class Book < ActiveRecord::Base
  include AttrSearchable

  attr_searchable :title, :description, :stock, :price, :created_at, :available
  attr_searchable :comment => ["comments.title", "comments.message"]
  attr_searchable :author => "author.name"
  # ...

  has_many :comments
  belongs_to :author
end

How does it work

AttrSearchable parses the query and maps it to an SQL Query using Arel. Thus, AttrSearchable is not bound to a specific RDBMS.

Book.search("stock > 0")
# ... WHERE books.stock > 0

Book.search("price > 10 stock > 0")
# ... WHERE books.price > 10 AND books.stock > 0

Book.search("Harry Potter")
# ... WHERE (books.title LIKE '%Harry%' OR books.description LIKE '%Harry%' OR ...) AND (books.title LIKE '%Potter%' OR books.description LIKE '%Potter%' ...)

Book.search("available:yes OR created_at:2014")
# ... WHERE books.available = 1 OR (books.created_at >= '2014-01-01 00:00:00' and books.created_at <= '2014-12-31 00:00:00')

Of course, these LIKE '%...%' queries won't achieve optimal performance, but check out the section below on AttrSearchable's fulltext capabilities to understand how the resulting queries can be optimized.

As Book.search(...) returns an ActiveRecord::Relation, you are free to pre- or post-process the search results in every possible way:

Book.where(:available => true).search("Harry Potter").order("books.id desc").paginate(:page => params[:page])

Fulltext index capabilities

By default, i.e. if you don't tell AttrSearchable about your fulltext indices, AttrSearchable will use LIKE '%...%' queries. Unfortunately, unless you create a trigram index (postgres only), theses queries can not use SQL indices, such that every row needs to be scanned by your RDBMS when you search for Book.search("Harry Potter") or similar, which is btw. usually ok for small data sets and a small amount of regular queries. Contrary, when you search for Book.search("title=Potter") indices can and will be used. Moreover, other indices (on price, stock, etc) will of course be used by your RDBMS when you search for Book.search("stock > 0"), etc.

Regarding the LIKE penalty, the easiest way to make them use indices is to remove the left wildcard. AttrSearchble supports this via:

class Book < ActiveRecord::Base
  # ...

  attr_searchable_options, :title, :left_wildcard => false

  # ...
end

However, this is often not desirable. Therefore, AttrSearchable can exploit the fulltext index capabilities of MySQL and PostgreSQL. To use already existing fulltext indices, simply tell AttrSearchable to use them via:

class Book < ActiveRecord::Base
  # ...

  attr_searchable_options :title, :type => :fulltext
  attr_searchable_options :author, :type => :fulltext

  # ...
end

AttrSearchable will then transparently change its SQL queries for the attributes having fulltext indices to:

Book.search("Harry Potter")
# MySQL: ... WHERE (MATCH(books.title) AGAINST('+Harry' IN BOOLEAN MODE) OR MATCH(books.author) AGAINST('+Harry' IN BOOLEAN MODE)) AND (MATCH(books.title) AGAINST ('+Potter' IN BOOLEAN MODE) OR MATCH(books.author) AGAINST('+Potter' IN BOOLEAN MODE))
# PostgreSQL: ... WHERE (to_tsvector('simple', books.title) @@ to_tsquery('simple', 'Harry') OR to_tsvector('simple', books.author) @@ to_tsquery('simple', 'Harry')) AND (to_tsvector('simple', books.title) @@ to_tsquery('simple', 'Potter') OR to_tsvector('simple', books.author) @@ to_tsquery('simple', 'Potter'))

Obviously, theses queries won't always return the same results as wildcard LIKE queries, because we search for words instead of substrings. However, fulltext indices will usually of course provide better performance.

Moreover, the query above is not yet perfect. To improve it even more, AttrSearchable tries to optimize the queries to make optimal use of fulltext indices while still allowing to mix them with non-fulltext attributes. To improve queries, the first thing you want to do is to specify a default field to search in, such that AttrSearchable must no longer search within all fields:

attr_searchable :all => [:author, :title]
attr_searchable_options :all, :type => :fulltext, :default => true

Now AttrSearchable can optimize the following, not yet optimal query:

BookSearch("Rowling OR Tolkien stock > 1")
# MySQL: ... WHERE ((MATCH(books.author) AGAINST('+Rowling' IN BOOLEAN MODE) OR MATCH(books.title) AGAINST('+Rowling' IN BOOLEAN MODE)) OR (MATCH(books.author) AGAINST('+Tolkien' IN BOOLEAN MODE) OR MATCH(books.title) AGAINST('+Tolkien' IN BOOLEAN MODE))) AND books.stock > 1
# PostgreSQL: ... WHERE ((to_tsvector('simple', books.author) @@ to_tsquery('simple', 'Rowling') OR to_tsvector('simple', books.title) @@ to_tsquery('simple', 'Rowling')) OR (to_tsvector('simple', books.author) @@ to_tsquery('simple', 'Tolkien') OR to_tsvector('simple', books.title) @@ to_tsquery('simple', 'Tolkien'))) AND books.stock > 1

to the following, more performant query:

BookSearch("Rowling OR Tolkien stock > 1")
# MySQL: ... WHERE MATCH(books.author, books.title) AGAINST('Rowling Tolkien' IN BOOLEAN MODE) AND books.stock > 1
# PostgreSQL: ... WHERE to_tsvector('simple', books.author || ' ' || books.title) @@ to_tsquery('simple', 'Rowling | Tokien') and books.stock > 1

Other queries will be optimized in a similar way, such that AttrSearchable tries to minimize the fultext constraints within a query, namely MATCH() AGAINST() for MySQL and to_tsvector() @@ to_tsquery() for PostgreSQL.

BookSearch("(Rowling -Potter) OR Tolkien")
# MySQL: ... WHERE MATCH(books.author, books.title) AGAINST('(+Rowling -Potter) Tolkien' IN BOOLEAN MODE)
# PostgreSQL: ... WHERE to_tsvector('simple', books.author || ' ' || books.title) @@ to_tsquery('simple', '(Rowling & !Potter) | Tolkien')

To create a fulltext index on books.title in MySQL, simply use:

add_index :books, :title, :type => :fulltext

Regarding compound indices, which will e.g. be used for the default field all we already specified above, use:

add_index :books, [:author, :title], :type => :fulltext

Please note that MySQL supports fulltext indices for MyISAM and, as of MySQL version 5.6+, for InnoDB as well. For more details about MySQL fulltext indices visit http://dev.mysql.com/doc/refman/5.6/en/fulltext-search.html

Regarding PostgreSQL there are more ways to create a fulltext index. However, one of the easiest ways is:

ActiveRecord::Base.connection.execute "CREATE INDEX fulltext_index_books_on_title ON books USING GIN(to_tsvector('simple', title))"

Regarding compound indices for PostgreSQL, use:

ActiveRecord::Base.connection.execute "CREATE INDEX fulltext_index_books_on_title ON books USING GIN(to_tsvector('simple', author || ' ' || title))"

To use another PostgreSQL dictionary than simple, you have to create the index accordingly and you need tell AttrSearchable about it, e.g.:

attr_searchable_options :title, :dictionary => "english"

For more details about PostgreSQL fulltext indices visit http://www.postgresql.org/docs/9.3/static/textsearch.html

Associations

If you specify searchable attributes from another model, like

class Book < ActiveRecord::Base
  # ...

  attr_searchable :author => "author.name"

  # ...
end

AttrSearchable will by default eager_load these associations, when you perform Book.search(...). If you don't want that or need to perform special operations, define a search_scope within your model:

class Book < ActiveRecord::Base
  # ...

  scope :search_scope, lambda { joins(:author).eager_load(:comments) } # etc.

  # ...
end

AttrSearchable will then skip any association auto loading and will use the search_scope instead.

Supported operators

Query string queries support AND/and, OR/or, :, =, !=, <, <=, >, >=, NOT/not/-, (), "..." and '...'. Default operators are AND and matches, OR has precedence over AND. NOT can only be used as infix operator regarding a single attribute.

Hash based queries support :and => [...] and :or => [...], which take an array of :not => {...}, :matches => {...}, :eq => {...}, :not_eq => {...}, :lt => {...}, :lteq => {...}, gt => {...}, :gteq => {...} and :query => "..." arguments. Moreover, :query => "..." makes it possible to create sub-queries. The other rules for query string queries apply to hash based queries as well.

Mapping

When searching in boolean, datetime, timestamp, etc. fields, AttrSearchable performs some mapping. The following queries are equivalent:

Book.search("available:true")
Book.search("available:1")
Book.search("available:yes")

as well as

Book.search("available:false")
Book.search("available:0")
Book.search("available:no")

For datetime and timestamp fields, AttrSearchable expands certain values to ranges:

Book.search("created_at:2014")
# ... WHERE created_at >= '2014-01-01 00:00:00' AND created_at <= '2014-12-31 23:59:59'

Book.search("created_at:2014-06")
# ... WHERE created_at >= '2014-06-01 00:00:00' AND created_at <= '2014-06-30 23:59:59'

Book.search("created_at:2014-06-15")
# ... WHERE created_at >= '2014-06-15 00:00:00' AND created_at <= '2014-06-15 23:59:59'

Chaining

Chaining of searches is possible. However, chaining does currently not allow AttrSearchable to optimize the individual queries for fulltext indices.

Book.search("Harry").search("Potter")

will generate

# MySQL: ... WHERE MATCH(...) AGAINST('+Harry' IN BOOLEAN MODE) AND MATCH(...) AGAINST('+Potter' IN BOOLEAN MODE)
# PostgreSQL: ... WHERE to_tsvector(...) @@ to_tsquery('simple', 'Harry') AND to_tsvector(...) @@ to_tsquery('simple', 'Potter')

instead of

# MySQL: ... WHERE MATCH(...) AGAINST('+Harry +Potter' IN BOOLEAN MODE)
# PostgreSQL: ... WHERE to_tsvector(...) @@ to_tsquery('simple', 'Harry & Potter')

Thus, if you use fulltext indices, you better avoid chaining.

Debugging

AttrSearchable conveniently hides certain errors, like parse errors, and instead returns an empty relation. However, if you need to debug certain cases, use Model#unsafe_search, which will raise them.

Book.unsafe_search("stock: None") # => raise AttrSearchable::IncompatibleDatatype

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request