CouchRest::Pager for paging through views

lib/pager.rb

@@ -0,0 +1,89 @@
+# paginate though 'gcharts/mp3-trk-dom-map' view and save
+
+# get 1000 records
+# truncate so that the key of the last record is not included in the page
+#  that key will be the first of the next page
+# (if the last key equals the first key, up the page size)
+# group the results by key
+# yield the group
+
+require File.dirname(__FILE__) + '/couchrest'
+
+module Enumerable
+  def group_by
+    inject({}) do |grouped, element|
+      (grouped[yield(element)] ||= []) << element
+      grouped
+    end
+  end unless [].respond_to?(:group_by)
+end
+
+class CouchRest
+  class Pager
+    attr_accessor :db
+    def initialize db
+      @db = db
+    end
+    
+    def key_reduce(view, count, firstkey = nil, lastkey = nil, &block)
+      # start with no keys
+      startkey = firstkey
+      # lastprocessedkey = nil
+      keepgoing = true
+      
+      while keepgoing && viewrows = request_view(view, count, startkey)
+        startkey = viewrows.first['key']
+        endkey = viewrows.last['key']
+
+        if (startkey == endkey)
+          # we need to rerequest to get a bigger page
+          # so we know we have all the rows for that key
+          viewrows = @db.view(view, :key => startkey)['rows']
+          # we need to do an offset thing to find the next startkey
+          # otherwise we just get stuck
+          lastdocid = viewrows.last['id']
+          fornextloop = @db.view(view, :startkey => startkey, :startkey_docid => lastdocid, :count => 2)['rows']
+
+          newendkey = fornextloop.last['key']
+          if (newendkey == endkey)
+            keepgoing = false
+          else
+            startkey = newendkey
+          end
+          rows = viewrows
+        else
+          rows = []
+          for r in viewrows
+            if (lastkey && r['key'] == lastkey)
+              keepgoing = false
+              break
+            end
+            break if (r['key'] == endkey)
+            rows << r
+          end   
+          startkey = endkey
+        end
+
+        grouped = rows.group_by{|r|r['key']}
+        grouped.each do |k, rs|
+          vs = rs.collect{|r|r['value']}
+          yield(k,vs)
+        end
+        
+        # lastprocessedkey = rows.last['key']
+      end
+    end
+
+    def request_view view, count = nil, startkey = nil, endkey = nil
+      opts = {}
+      opts[:count] = count if count
+      opts[:startkey] = startkey if startkey
+      opts[:endkey] = endkey if endkey
+      
+      results = @db.view(view, opts)
+      rows = results['rows']
+      rows unless rows.length == 0
+    end
+
+  end
+end