chain.rb in dynamoid-0.4.0

- old
+ new

@@ -4,24 +4,25 @@
 
     # The criteria chain is equivalent to an ActiveRecord relation (and realistically I should change the name from
     # chain to relation). It is a chainable object that builds up a query and eventually executes it either on an index
     # or by a full table scan.
     class Chain
-      attr_accessor :query, :source, :index, :values
+      attr_accessor :query, :source, :index, :values, :limit, :start, :consistent_read
       include Enumerable
-      
+
       # Create a new criteria chain.
       #
       # @param [Class] source the class upon which the ultimate query will be performed.
       def initialize(source)
         @query = {}
         @source = source
+        @consistent_read = false
       end
-      
-      # The workhorse method of the criteria chain. Each key in the passed in hash will become another criteria that the 
-      # ultimate query must match. A key can either be a symbol or a string, and should be an attribute name or 
-      # an attribute name with a range operator. 
+
+      # The workhorse method of the criteria chain. Each key in the passed in hash will become another criteria that the
+      # ultimate query must match. A key can either be a symbol or a string, and should be an attribute name or
+      # an attribute name with a range operator.
       #
       # @example A simple criteria
       #   where(:name => 'Josh')
       #
       # @example A more complicated criteria
@@ -30,122 +31,196 @@
       # @since 0.2.0
       def where(args)
         args.each {|k, v| query[k] = v}
         self
       end
-      
+
+      def consistent
+        @consistent_read = true
+        self
+      end
+
       # Returns all the records matching the criteria.
       #
       # @since 0.2.0
       def all
         records
       end
 
       # Returns the first record matching the criteria.
       #
-      # @since 0.2.0      
+      # @since 0.2.0
       def first
-        records.first
+        limit(1).first
       end
 
+      def limit(limit)
+        @limit = limit
+        records
+      end
+
+      def start(start)
+        @start = start
+        self
+      end
+
       # Allows you to use the results of a search as an enumerable over the results found.
       #
-      # @since 0.2.0            
+      # @since 0.2.0
       def each(&block)
         records.each(&block)
       end
-      
+
+      def consistent_opts
+        { :consistent_read => consistent_read }
+      end
+
       private
-      
+
       # The actual records referenced by the association.
       #
       # @return [Array] an array of the found records.
       #
       # @since 0.2.0
       def records
-        return records_with_index if index
-        records_without_index
+        if range?
+          records_with_range
+        elsif index
+          records_with_index
+        else
+          records_without_index
+        end
       end
 
       # If the query matches an index on the associated class, then this method will retrieve results from the index table.
       #
       # @return [Array] an array of the found records.
       #
-      # @since 0.2.0      
+      # @since 0.2.0
       def records_with_index
         ids = if index.range_key?
           Dynamoid::Adapter.query(index.table_name, index_query).collect{|r| r[:ids]}.inject(Set.new) {|set, result| set + result}
         else
-          results = Dynamoid::Adapter.read(index.table_name, index_query[:hash_value])
+          results = Dynamoid::Adapter.read(index.table_name, index_query[:hash_value], consistent_opts)
           if results
             results[:ids]
           else
             []
           end
         end
         if ids.nil? || ids.empty?
           []
         else
-          Array(source.find(ids.to_a))
+          ids = ids.to_a
+
+          if @start
+            ids = ids.drop_while { |id| id != @start.hash_key }.drop(1)
+          end
+
+          ids = ids.take(@limit) if @limit
+          Array(source.find(ids, consistent_opts))
         end
       end
-      
-      # If the query does not match an index, we'll manually scan the associated table to manually find results.
+
+      def records_with_range
+        Dynamoid::Adapter.query(source.table_name, range_query).collect {|hash| source.new(hash).tap { |r| r.new_record = false } }
+      end
+
+      # If the query does not match an index, we'll manually scan the associated table to find results.
       #
       # @return [Array] an array of the found records.
       #
-      # @since 0.2.0      
+      # @since 0.2.0
       def records_without_index
         if Dynamoid::Config.warn_on_scan
           Dynamoid.logger.warn 'Queries without an index are forced to use scan and are generally much slower than indexed queries!'
           Dynamoid.logger.warn "You can index this query by adding this to #{source.to_s.downcase}.rb: index [#{source.attributes.sort.collect{|attr| ":#{attr}"}.join(', ')}]"
         end
-        Dynamoid::Adapter.scan(source.table_name, query).collect {|hash| source.new(hash).tap { |r| r.new_record = false } }
+
+        Dynamoid::Adapter.scan(source.table_name, query, query_opts).collect {|hash| source.new(hash).tap { |r| r.new_record = false } }
       end
-      
-      # Format the provided query so that it can be used to query results from DynamoDB. 
+
+      # Format the provided query so that it can be used to query results from DynamoDB.
       #
       # @return [Hash] a hash with keys of :hash_value and :range_value
       #
-      # @since 0.2.0      
+      # @since 0.2.0
       def index_query
         values = index.values(query)
         {}.tap do |hash|
           hash[:hash_value] = values[:hash_value]
           if index.range_key?
             key = query.keys.find{|k| k.to_s.include?('.')}
             if key
-              if query[key].is_a?(Range)
-                hash[:range_value] = query[key]
-              else
-                val = query[key].to_f
-                case key.split('.').last
-                when 'gt'
-                  hash[:range_greater_than] = val
-                when 'lt'
-                  hash[:range_less_than] = val
-                when 'gte'
-                  hash[:range_gte] = val
-                when 'lte'
-                  hash[:range_lte] = val
-                end
-              end
+              hash.merge!(range_hash(key))
             else
               raise Dynamoid::Errors::MissingRangeKey, 'This index requires a range key'
             end
           end
         end
       end
 
+      def range_hash(key)
+        val = query[key]
+
+        return { :range_value => query[key] } if query[key].is_a?(Range)
+
+        case key.split('.').last
+        when 'gt'
+          { :range_greater_than => val.to_f }
+        when 'lt'
+          { :range_less_than  => val.to_f }
+        when 'gte'
+          { :range_gte  => val.to_f }
+        when 'lte'
+          { :range_lte => val.to_f }
+        when 'begins_with'
+          { :range_begins_with => val }
+        end
+      end
+
+      def range_query
+        opts = { :hash_value => query[source.hash_key] }
+        if key = query.keys.find { |k| k.to_s.include?('.') }
+          opts.merge!(range_key(key))
+        end
+        opts.merge(query_opts).merge(consistent_opts)
+      end
+
       # Return an index that fulfills all the attributes the criteria is querying, or nil if none is found.
       #
-      # @since 0.2.0            
+      # @since 0.2.0
       def index
-        index = source.find_index(query.keys.collect{|k| k.to_s.split('.').first})
+        index = source.find_index(query_keys)
         return nil if index.blank?
         index
       end
+
+      def query_keys
+        query.keys.collect{|k| k.to_s.split('.').first}
+      end
+
+      def range?
+        return false unless source.range_key
+        query_keys == ['id'] || (query_keys.to_set == ['id', source.range_key.to_s].to_set)
+      end
+
+      def start_key
+        key = { :hash_key_element => { 'S' => @start.hash_key } }
+        if range_key = @start.class.range_key
+          range_key_type = @start.class.attributes[range_key][:type] == :string ? 'S' : 'N'
+          key.merge!({:range_key_element => { range_key_type => @start.send(range_key) } })
+        end
+        key
+      end
+
+      def query_opts
+        opts = {}
+        opts[:limit] = @limit if @limit
+        opts[:next_token] = start_key if @start
+        opts
+      end
     end
-    
+
   end
-  
+
 end