Module: Repertoire::Faceting::Model::ClassMethods

Defined in:
lib/repertoire-faceting/model.rb

Overview

Facet declarations

Facet declarations consist of a facet name and an optional ActiveRecord relation that describes the attribute column to facet over, any joins necessary to reach it, and other defaults. They work similarly to Rails scoped queries. For example:

class Nobelist < ActiveRecord::Base
  include Repertoire::Faceting::Model
  has_many :affiliations

  facet :discipline
  facet :degree,     joins(:affiliations).group('affiliations.degree')
  facet :birthdate,  order('birthdate ASC')
end

Implicitly, any facet declaration is an SQL aggregate that divides the attribute values into discrete groups. When no relation is provided, /model/.group(/facet name/) is assumed by default. So the discipline facet declaration above is equivalent to

facet :discipline, group(:discipline)

and the grouping on degree could be left out. You can use this behavior to construct a facet from differently-named columns:

facet :balloon_color, group(:color)

or to synthesize values using an SQL expression:

facet :birth_year, group('EXTRACT(year FROM birthdate)')

As shown above, facets can be constructed from an arbitrary set of joined tables.

Nested facets

Facets can be built from a nested hierarchy of values by providing multiple group columns. In this case, value counts are aggregated at each level in turn.

facet :birth_place, group(:birth_country, :birth_state, :birth_city)

As for basic facets, nested facets may consist of SQL expressions. This is particularly useful in faceting over data in more complex types such as dates or geographical regions:

facet :birth_date, group('EXTRACT(year FROM birthdate)', 'EXTRACT(month FROM birthdate)', 'EXTRACT(day FROM birthdate)')

Facet options

The following query options can also be specified in the facet declaration.

order

Order for facet value counts. Two computed columns are available, “count” and another with the facet’s name. For example, to order a genre facet alphanumerically within each descending count:

facet :genre, order('count DESC', 'genre ASC')
nils

Whether to include null facet values in the results or not. Defaults to true:

facet :genre, nils(false)
minimum

Cut-off below which facet value counts should not be listed:

facet :genre, minimum(5)

Executing Queries

Facet value count and result queries follow the format familiar from ActiveRecord group and count aggregation. This allows you to execute a facet value count query given a base set of records.

Nobelist.where("name LIKE 'Robert%'").count(:discipline)

To incorporate refinements on other facets on this model, use refine:

Nobelist.refine(:nobel_year => 2001, :degree => 'Ph.D.').count(:discipline)

If you provide multiple values for a simple facet refinement, they are interpreted as a logical “or”:

Nobelist.refine(:nobel_year => [2000, 2001])     # => 'WHERE name IN (2000, 2001)'

In the case of a nested facet, multiple values identify levels in the taxonomy:

Nobelist.refine(:birth_place => [ 'Ukraine', 'Kiev' ]).count(:nobel_year)

Refinements are integrated into result queries automatically:

Nobelist.refine(:birth_place => [ 'Ukraine', 'Kiev' ]).all

Index access

As you will have noted already, facet counts and queries are quite similar to their ActiveRecord/SQL counterparts. Behind the scenes, the Repertoire faceting code re-writes your query.

Facets defined on associations are joined and limited automatically, and facet indices in the database are used wherever possible rather than querying the model table.

Facet registration

The system supports plugins for new facet type implementations. When a new facet is declared, the available facet implementations are polled until one claims the new relation. For example, of the built-in facet implementations, BasicFacet claims facets with a single group column, and NestedFacet claims those with several group columns. If several facet implementations claim a facet, the one that registered later wins.

See AbstractFacet for more details.

Instance Method Summary collapse

Instance Method Details

#facet(name, rel = nil) ⇒ Object

Declare a facet by name



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# File 'lib/repertoire-faceting/model.rb', line 125

def facet(name, rel=nil)
  name = name.to_sym

  # default: group by column with facet name, order by count descending
  rel ||= scoped_all
  rel = rel.group(name)                           if rel.group_values.empty?
  rel = rel.order(["count DESC", "#{name} ASC"])  if rel.order_values.empty?

  # locate facet implementation that can handle relation
  facets[name] = Facets::AbstractFacet.mixin(name, rel)
end

#facet?(name) ⇒ Boolean

Is there a facet by this name?

Returns:

  • (Boolean) 


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# File 'lib/repertoire-faceting/model.rb', line 138

def facet?(name)
  facets.key?(name.to_sym)
end

#facet_names ⇒ Object

All defined facets by name



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# File 'lib/repertoire-faceting/model.rb', line 143

def facet_names
  facets.keys
end

#faceting_id ⇒ Object

Returns the name of the id column to use for constructing bitset signatures over this model.



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# File 'lib/repertoire-faceting/model.rb', line 247

def faceting_id
  @faceting_id ||= [PACKED_SIGNATURE_COLUMN, DEFAULT_SIGNATURE_COLUMN].detect { |c| column_names.include?(c) }
end

#index_facets(next_indexes = nil, next_faceting_id = nil) ⇒ Object

Drops any unused facet indices, updates its packed ids, then recreates indices for the facets with the provided names. If no names are provided, then the existing facet indices are refreshed.

If a signature id column name is provided, it will be used to build the bitset indices. Otherwise the indexer will add or remove a new packed id column as appropriate.

Examples:

Refresh existing facet indices

Nobelist.index_facets

Adjust which facets are indexed

Nobelist.index_facets([:degree, :nobel_year])

Drop all facet indices, but add/remove packed id as necessary

Nobelist.index_facets([])

Drop absolutely everything, force manual faceting using ‘id’

  column

Nobelist.index_facets([], 'id')



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# File 'lib/repertoire-faceting/model.rb', line 179

def index_facets(next_indexes=nil, next_faceting_id=nil)
  # default: update existing facets
  current_indexes = indexed_facets
  next_indexes ||= current_indexes

  # sanity checks
  current_indexes = current_indexes.map { |name| name.to_sym }
  next_indexes    = next_indexes.map    { |name| name.to_sym }
  (current_indexes | next_indexes).each do
    |name| raise QueryError, "Unknown facet #{name}" unless facet?(name)
  end

  # determine best column for signature bitsets, unless set manually
  next_faceting_id ||= if signature_wastage(DEFAULT_SIGNATURE_COLUMN) < SIGNATURE_WASTAGE_THRESHOLD
    DEFAULT_SIGNATURE_COLUMN
  else
    PACKED_SIGNATURE_COLUMN
  end

  # default behavior: no changes to packed id column
  drop_packed_id = create_packed_id = false

  # default behavior: adjust facet indexes
  drop_list    = current_indexes - next_indexes
  refresh_list = next_indexes & current_indexes
  create_list  = next_indexes - current_indexes

  # adding or removing a packed id column
  if next_faceting_id != faceting_id
    drop_packed_id   = (next_faceting_id == DEFAULT_SIGNATURE_COLUMN)
    create_packed_id = (next_faceting_id != DEFAULT_SIGNATURE_COLUMN)
  end

  # special case: repacking an existing packed id column
  if next_faceting_id == faceting_id && next_faceting_id != DEFAULT_SIGNATURE_COLUMN
    drop_packed_id = create_packed_id = (signature_wastage > SIGNATURE_WASTAGE_THRESHOLD)
  end

  # changing item ids invalidates all existing facet indices
  if drop_packed_id || create_packed_id
    drop_list, refresh_list, create_list = [ current_indexes, [], next_indexes ]
  end

  connection.transaction do
    # adjust faceting id column
    connection.remove_column(table_name, PACKED_SIGNATURE_COLUMN)           if drop_packed_id
    connection.add_column(table_name, PACKED_SIGNATURE_COLUMN, "SERIAL")    if create_packed_id
    @faceting_id = next_faceting_id

    # adjust facet indices
    drop_list.each    { |name| facets[name].drop_index }
    refresh_list.each { |name| facets[name].refresh_index }
    create_list.each  { |name| facets[name].create_index }
  end

  # TODO. in a nested transaction, this would need to fire after the final commit...
  reset_column_information

end

#indexed_facets ⇒ Object

Returns a list of the facets that currently have indices declared



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# File 'lib/repertoire-faceting/model.rb', line 148

def indexed_facets
  connection.indexed_facets(table_name)
end

#reset_column_information ⇒ Object

Over-rides reset_column_information in ActiveRecord::ModelSchema



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# File 'lib/repertoire-faceting/model.rb', line 240

def reset_column_information
  @faceting_id = nil
  super
end

#scoped_all ⇒ Object

Once clients have migrated to Rails 4, delete and replace with ‘all’ where this is called

c.f. stackoverflow.com/questions/18198963/with-rails-4-model-scoped-is-deprecated-but-model-all-cant-replace-it



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# File 'lib/repertoire-faceting/model.rb', line 260

def scoped_all
  where(nil)
end

#signature_wastage(signature_column = nil) ⇒ Object

Returns the proportion of wasted slots in 0..max(id)



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# File 'lib/repertoire-faceting/model.rb', line 252

def signature_wastage(signature_column = nil)
  signature_column ||= faceting_id
  connection.signature_wastage(table_name, signature_column)
end