Class: CouchRest::Model::Designs::View

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/couchrest/model/designs/view.rb

Overview

A proxy class that allows view queries to be created using chained method calls. After each call a new instance of the method is created based on the original in a similar fashion to ruby's Sequel library, or Rails 3's Arel.

CouchDB views have inherent limitations, so joins and filters as used in a normal relational database are not possible.

Instance Attribute Summary (collapse)

Class Method Summary (collapse)

Instance Method Summary (collapse)

Constructor Details

- (View) initialize(design_doc, parent, new_query = {}, name = nil)

Initialize a new View object. This method should not be called from outside CouchRest Model.



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# File 'lib/couchrest/model/designs/view.rb', line 21

def initialize(design_doc, parent, new_query = {}, name = nil)
  self.design_doc = design_doc
  proxy = new_query.delete(:proxy)
  if parent.is_a?(Class) && parent < CouchRest::Model::Base
    raise "Name must be provided for view to be initialized" if name.nil?
    self.model    = (proxy || parent)
    self.owner    = parent
    self.name     = name.to_s
    # Default options:
    self.query    = { }
  elsif parent.is_a?(self.class)
    self.model    = (proxy || parent.model)
    self.owner    = parent.owner
    self.name     = parent.name
    self.query    = parent.query.dup
  else
    raise "View cannot be initialized without a parent Model or View"
  end
  query.update(new_query)
  super()
end

Instance Attribute Details

- (Object) design_doc

Returns the value of attribute design_doc



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# File 'lib/couchrest/model/designs/view.rb', line 17

def design_doc
  @design_doc
end

- (Object) model

Returns the value of attribute model



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# File 'lib/couchrest/model/designs/view.rb', line 17

def model
  @model
end

- (Object) name

Returns the value of attribute name



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# File 'lib/couchrest/model/designs/view.rb', line 17

def name
  @name
end

- (Object) owner

Returns the value of attribute owner



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# File 'lib/couchrest/model/designs/view.rb', line 17

def owner
  @owner
end

- (Object) query

Returns the value of attribute query



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# File 'lib/couchrest/model/designs/view.rb', line 17

def query
  @query
end

- (Object) result

Returns the value of attribute result



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# File 'lib/couchrest/model/designs/view.rb', line 17

def result
  @result
end

Class Method Details

+ (Object) create_model_methods(design_doc, name, opts = {})



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# File 'lib/couchrest/model/designs/view.rb', line 505

def create_model_methods(design_doc, name, opts = {})
  method = design_doc.method_name
  design_doc.model.instance_eval <<-EOS, __FILE__, __LINE__ + 1
    def #{name}(opts = {})
      #{method}.view('#{name}', opts)
    end
    def find_#{name}(*key)
      #{name}.key(*key).first()
    end
  EOS
end

+ (Object) define(design_doc, name, opts = {})

Simplified view definition. A new view will be added to the provided design document using the name and options.

If the view name starts with "by_" and :by is not provided in the options, the new view's map method will be interpreted and generated automatically. For example:

View.define(Meeting, design, "by_date_and_name")

Will create a view that searches by the date and name properties. Explicity setting the attributes to use is possible using the :by option. For example:

View.define(Meeting, design, "by_date_and_name", :by => [:date, :firstname, :lastname])

The view name is the same, but three keys would be used in the subsecuent index.

By default, a check is made on each of the view's keys to ensure they do not contain a nil value ('null' in javascript). This is probably what you want in most cases but sometimes in can be useful to create an index where nil is permited. Set the :allow_nil option to true to remove this check.

Conversely, keys are not checked to see if they are empty or blank. If you'd like to enable this, set the :allow_blank option to false. The default is true, empty strings are permited in the indexes.



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# File 'lib/couchrest/model/designs/view.rb', line 455

def define(design_doc, name, opts = {})
  model = design_doc.model

  # Is this an all view?
  if name.to_s == 'all'
    opts[:map] = <<-EOF
      function(doc) {
        if (doc['#{model.model_type_key}'] == '#{model.to_s}') {
          emit(doc._id, null);
        }
      }
    EOF
  elsif !opts[:map]
    if opts[:by].nil? && name.to_s =~ /^by_(.+)/
      opts[:by] = $1.split(/_and_/)
    end
    raise "View cannot be created without recognised name, :map or :by options" if opts[:by].nil?

    opts[:allow_blank] = opts[:allow_blank].nil? ? true : opts[:allow_blank]
    opts[:guards] ||= []
    opts[:guards].push "(doc['#{model.model_type_key}'] == '#{model.to_s}')"

    keys = opts[:by].map{|o| "doc['#{o}']"}
    emit = keys.length == 1 ? keys.first : "[#{keys.join(', ')}]"
    opts[:guards] += keys.map{|k| "(#{k} != null)"} unless opts[:allow_nil]
    opts[:guards] += keys.map{|k| "(#{k} != '')"} unless opts[:allow_blank]
    opts[:map] = <<-EOF
      function(doc) {
        if (#{opts[:guards].join(' && ')}) {
          emit(#{emit}, 1);
        }
      }
    EOF
    if opts[:reduce].nil?
      opts[:reduce] = <<-EOF
        function(key, values, rereduce) {
          return sum(values);
        }
      EOF
    end
  end

  design_doc['views'] ||= {}
  view = design_doc['views'][name.to_s] = { }
  view['map'] = opts[:map]
  view['reduce'] = opts[:reduce] if opts[:reduce]
  view
end

+ (Object) define_and_create(design_doc, name, opts = {})



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# File 'lib/couchrest/model/designs/view.rb', line 422

def define_and_create(design_doc, name, opts = {})
  define(design_doc, name, opts)
  create_model_methods(design_doc, name, opts)
end

Instance Method Details

- (Object) [](value)

Accept requests as if the view was an array. Used for backwards compatibity with older queries:

Model.all(:raw => true, :limit => 0)['total_rows']

In this example, the raw option will be ignored, and the total rows will still be accessible.



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# File 'lib/couchrest/model/designs/view.rb', line 165

def [](value)
  execute[value]
end

- (Object) all

Fetch all the documents the view can access. If the view has not already been prepared for including documents in the query, it will be added automatically and reset any previously cached results.



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# File 'lib/couchrest/model/designs/view.rb', line 64

def all
  include_docs!
  docs
end

- (Object) count

Perform a count operation based on the current view. If the view can be reduced, the reduce will be performed and return the first value. This is okay for most simple queries, but may provide unexpected results if your reduce method does not calculate the total number of documents in a result set.

Trying to use this method with the group option will raise an error.

If no reduce function is defined, a query will be performed to return the total number of rows, this is the equivalant of:

view.limit(0).total_rows


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# File 'lib/couchrest/model/designs/view.rb', line 115

def count
  raise "View#count cannot be used with group options" if query[:group]
  if can_reduce?
    row = reduce.skip(0).limit(1).rows.first
    row.nil? ? 0 : row.value
  else
    limit(0).total_rows
  end
end

- (Object) current_page



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# File 'lib/couchrest/model/designs/view.rb', line 378

def current_page
  (offset_value / limit_value) + 1
end

- (Object) database(value)

Specify the database the view should use. If not defined, an attempt will be made to load its value from the model.



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# File 'lib/couchrest/model/designs/view.rb', line 319

def database(value)
  update_query(:database => value)
end

- (Object) descending

The results should be provided in descending order. If the startkey or endkey query options have already been seen set, calling this method will automatically swap the options around. If you don't want this, simply set descending before any other option.

Descending is false by default, and this method cannot be undone once used, it has no inverse option.



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# File 'lib/couchrest/model/designs/view.rb', line 251

def descending
  if query[:startkey] || query[:endkey]
    query[:startkey], query[:endkey] = query[:endkey], query[:startkey]
  elsif query[:startkey_docid] || query[:endkey_docid]
    query[:startkey_docid], query[:endkey_docid] = query[:endkey_docid], query[:startkey_docid]
  end
  update_query(:descending => true)
end

- (Object) docs

Provide all the documents from the view. If the view has not been prepared with the include_docs option, each document will be loaded individually.



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# File 'lib/couchrest/model/designs/view.rb', line 72

def docs
  @docs ||= rows.map{|r| r.doc}
end

- (Object) each(&block)

Run through each document provided by the #all method. This is also used by the Enumerator mixin to provide all the standard ruby collection directly on the view.



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# File 'lib/couchrest/model/designs/view.rb', line 135

def each(&block)
  all.each(&block)
end

- (Boolean) empty?

Check to see if the array of documents is empty. This will perform the query and return all documents ready to use, if you don't want to load anything, use #total_rows or #count instead.



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# File 'lib/couchrest/model/designs/view.rb', line 128

def empty?
  all.empty?
end

- (Object) endkey(value)

The opposite of #startkey, finds all index entries whose key is before the value specified.

See the #startkey method for more details and the #inclusive_end option.



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# File 'lib/couchrest/model/designs/view.rb', line 215

def endkey(value)
  raise "View#endkey cannot be used when key has been set" unless query[:key].nil? && query[:keys].nil?
  update_query(:endkey => value)
end

- (Object) endkey_doc(value)

The result set should end at the position of the provided document. The value may be provided as an object that responds to the #id call or a string.



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# File 'lib/couchrest/model/designs/view.rb', line 223

def endkey_doc(value)
  update_query(:endkey_docid => value.is_a?(String) ? value : value.id)
end

- (Object) first

If another request has been made on the view, this will return the first document in the set. If not, a new query object will be generated with a limit of 1 so that only the first document is loaded.



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# File 'lib/couchrest/model/designs/view.rb', line 80

def first
  result ? all.first : limit(1).all.first
end

- (Object) group

Control whether the reduce function reduces to a set of distinct keys or to a single result row.

By default the value is false, and can only be set when the view's #reduce option has been set.



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# File 'lib/couchrest/model/designs/view.rb', line 287

def group
  raise "View#reduce must have been set before grouping is permitted" unless query[:reduce]
  update_query(:group => true)
end

- (Object) group_level(value)

Will set the level the grouping should be performed to. As per the CouchDB API, it only makes sense when the index key is an array.

This will automatically set the group option.



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# File 'lib/couchrest/model/designs/view.rb', line 296

def group_level(value)
  group.update_query(:group_level => value.to_i)
end

- (Object) include_docs



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# File 'lib/couchrest/model/designs/view.rb', line 300

def include_docs
  update_query.include_docs!
end

- (Object) info

No yet implemented. Eventually this will provide a raw hash of the information CouchDB holds about the view.



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# File 'lib/couchrest/model/designs/view.rb', line 171

def info
  raise "Not yet implemented"
end

- (Object) key(value)

Find all entries in the index whose key matches the value provided.

Cannot be used when the #startkey or #endkey have been set.



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# File 'lib/couchrest/model/designs/view.rb', line 186

def key(value)
  raise "View#key cannot be used when startkey or endkey have been set" unless query[:keys].nil? && query[:startkey].nil? && query[:endkey].nil?
  update_query(:key => value)
end

- (Object) keys(*keys)

Keys is a special CouchDB option that will cause the view request to be POSTed including an array of keys. Only documents with the matching keys will be returned. This is much faster than sending multiple requests for a set non-consecutive documents.

If no values are provided, this method will act as a wrapper around the rows result set, providing an array of keys.



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# File 'lib/couchrest/model/designs/view.rb', line 234

def keys(*keys)
  if keys.empty?
    rows.map{|r| r.key}
  else
    raise "View#keys cannot by used when key or startkey/endkey have been set" unless query[:key].nil? && query[:startkey].nil? && query[:endkey].nil?
    update_query(:keys => keys.first)
  end
end

- (Object) last

Same as first but will order the view in descending order. This does not however reverse the search keys or the offset, so if you are using a startkey and endkey you might end up with unexpected results.

If in doubt, don't use this method!



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# File 'lib/couchrest/model/designs/view.rb', line 91

def last
  result ? all.last : limit(1).descending.all.last
end

- (Object) length

Return the number of documents in the currently defined result set. Use #count for the total number of documents regardless of the current limit defined.



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# File 'lib/couchrest/model/designs/view.rb', line 98

def length
  docs.length
end

- (Object) limit(value)

Limit the result set to the value supplied.



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# File 'lib/couchrest/model/designs/view.rb', line 261

def limit(value)
  update_query(:limit => value)
end

- (Object) limit_value



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# File 'lib/couchrest/model/designs/view.rb', line 370

def limit_value
  query[:limit]
end

- (Object) num_pages



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# File 'lib/couchrest/model/designs/view.rb', line 374

def num_pages
  (total_count.to_f / limit_value).ceil
end

- (Object) offset

Wrapper for the results offset. As per the CouchDB API, this may be nil if groups are used.



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# File 'lib/couchrest/model/designs/view.rb', line 141

def offset
  execute['offset']
end

- (Object) offset_value



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# File 'lib/couchrest/model/designs/view.rb', line 366

def offset_value
  query[:skip]
end

- (Object) page(page)

Kaminari compatible pagination support

Based on the really simple support for scoped pagination in the the Kaminari gem, we provide compatible methods here to perform the same actions you'd expect.



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# File 'lib/couchrest/model/designs/view.rb', line 349

def page(page)
  limit(owner.default_per_page).skip(owner.default_per_page * ([page.to_i, 1].max - 1))
end

- (Object) per(num)



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# File 'lib/couchrest/model/designs/view.rb', line 353

def per(num)
  raise "View#page must be called before #per!" if limit_value.nil? || offset_value.nil?
  if (n = num.to_i) <= 0
    self
  else
    limit(num).skip(offset_value / limit_value * n)
  end
end

- (Object) proxy(value)

Set the view's proxy that will be used instead of the model for any future searches. As soon as this enters the new view's initializer it will be removed and set as the model object.

See the Proxyable mixin for more details.



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# File 'lib/couchrest/model/designs/view.rb', line 330

def proxy(value)
  update_query(:proxy => value)
end

- (Object) reduce

Use the reduce function on the view. If none is available this method will fail.



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# File 'lib/couchrest/model/designs/view.rb', line 277

def reduce
  raise "Cannot reduce a view without a reduce method" unless can_reduce?
  update_query(:reduce => true, :include_docs => nil)
end

- (Object) reset!

Return any cached values to their nil state so that any queries requested later will have a fresh set of data.



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# File 'lib/couchrest/model/designs/view.rb', line 336

def reset!
  self.result = nil
  @rows = nil
  @docs = nil
end

- (Object) rows

Return each row wrapped in a ViewRow object. Unlike the raw CouchDB request, this will provide an empty array if there are no results.



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# File 'lib/couchrest/model/designs/view.rb', line 51

def rows
  return @rows if @rows
  if execute && result['rows']
    @rows ||= result['rows'].map{|v| ViewRow.new(v, model)}
  else 
    [ ]
  end
end

- (Object) skip(value = 0)

Skip the number of entries in the index specified by value. This would be the equivilent of an offset in SQL.

The CouchDB documentation states that the skip option should not be used with large data sets as it is inefficient. Use the startkey_doc method instead to skip ranges efficiently.



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# File 'lib/couchrest/model/designs/view.rb', line 271

def skip(value = 0)
  update_query(:skip => value)
end

- (Object) stale(value)

Allow the results of a query to be provided "stale". Setting to 'ok' will disable all view updates for the query. When 'update_after' is provided the index will be update after the result has been returned.



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# File 'lib/couchrest/model/designs/view.rb', line 310

def stale(value)
  unless (['ok', 'update_after'].include?(value.to_s))
    raise "View#stale can only be set with 'ok' or 'update_after'."
  end
  update_query(:stale => value.to_s)
end

- (Object) startkey(value)

Find all index keys that start with the value provided. May or may not be used in conjunction with the endkey option.

When the #descending option is used (not the default), the start and end keys should be reversed, as per the CouchDB API.

Cannot be used if the key has been set.



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# File 'lib/couchrest/model/designs/view.rb', line 198

def startkey(value)
  raise "View#startkey cannot be used when key has been set" unless query[:key].nil? && query[:keys].nil?
  update_query(:startkey => value)
end

- (Object) startkey_doc(value)

The result set should start from the position of the provided document. The value may be provided as an object that responds to the #id call or a string.



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# File 'lib/couchrest/model/designs/view.rb', line 206

def startkey_doc(value)
  update_query(:startkey_docid => value.is_a?(String) ? value : value.id)
end

- (Object) total_count



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# File 'lib/couchrest/model/designs/view.rb', line 362

def total_count
  @total_count ||= limit(nil).skip(nil).count
end

- (Object) total_rows

Wrapper for the total_rows value provided by the query. As per the CouchDB API, this may be nil if groups are used.



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# File 'lib/couchrest/model/designs/view.rb', line 147

def total_rows
  execute['total_rows']
end

- (Object) values

Convenience wrapper to provide all the values from the route set without having to go through rows.



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# File 'lib/couchrest/model/designs/view.rb', line 153

def values
  rows.map{|r| r.value}
end