couchrest_model/lib/couchrest/model/view.rb

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#### NOTE Work in progress! Not yet used!
module CouchRest
module Model
# 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. At least not yet!
#
#
#
class View
attr_accessor :query, :design, :database, :name
# Initialize a new View object. This method should not be called from outside CouchRest Model.
def initialize(parent, new_query = {}, name = nil)
if parent.is_a? Base
raise "Name must be provided for view to be initialized" if name.nil?
@name = name
@database = parent.database
@query = { :reduce => false }
elsif parent.is_a? View
@database = parent.database
@query = parent.query.dup
else
raise "View cannot be initialized without a parent Model or View"
end
@query.update(new_query)
super
end
# == View Execution Methods
#
# Send a request to the CouchDB database using the current query values.
# Inmediatly send a request to the database for all documents provided by the query.
#
def all(&block)
args = include_docs.query
end
# Inmediatly send a request for the first result of the dataset. This will override
# any limit set in the view previously.
def first(&block)
args = limit(1).include_docs.query
end
def info
end
def offset
end
def total_rows
end
def rows
end
# == View Filter Methods
#
# View filters return an copy of the view instance with the query
# modified appropriatly. Errors will be raised if the methods
# are combined in an incorrect fashion.
#
# Find all entries in the index whose key matches the value provided.
#
# Cannot be used when the +#startkey+ or +#endkey+ have been set.
def key(value)
raise "View#key cannot be used when startkey or endkey have been set" unless query[:startkey].nil? && query[:endkey].nil?
update_query(:key => value)
end
# 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.
#
# Cannot be used if the key has been set.
def startkey(value)
raise "View#startkey cannot be used when key has been set" unless query[:key].nil?
update_query(:startkey => value)
end
# 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.
def startkey_doc(value)
update_query(:startkey_docid => value.is_a?(String) ? value : value.id
end
# 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.
def endkey(value)
raise "View#endkey cannot be used when key has been set" unless query[:key].nil?
update_query(:endkey => value)
end
# 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.
def endkey_doc(value)
update_query(:endkey_docid => value.is_a?(String) ? value : value.id
end
# The results should be provided in descending order.
#
# Descending is false by default, this method will enable it and cannot be undone.
def descending
update_query(:descending => true)
end
# Limit the result set to the value supplied.
def limit(value)
update_query(:limit => value)
end
# 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.
def skip(value = 0)
update_query(:skip => value)
end
# Use the reduce function on the view. If none is available this method will fail.
def reduce
update_query(:reduce => true)
end
# 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.
def group
raise "View#reduce must have been set before grouping is permitted" unless query[:reduce]
update_query(:group => true)
end
def group_level(value)
raise "View#reduce and View#group must have been set before group_level is called" unless query[:reduce] && query[:group]
update_query(:group_level => value.to_i)
end
protected
def update_query(new_query = {})
self.class.new(self, new_query)
end
# Used internally to ensure that docs are provided. Should not be used outside of
# the view class under normal circumstances.
def include_docs
raise "Documents cannot be returned from a view that is prepared for a reduce" if query[:reduce]
update_query(:include_docs => true)
end
def execute(&block)
end
end
end
end