 
 	# this will only work on single node redis, not redis cluster
 	getProjectIdsWithHistoryOps: (callback = (error, project_ids) ->) ->
-		rclient.keys docsWithHistoryOpsKey("*"), (error, project_keys) ->
+		RedisManager._getKeys docsWithHistoryOpsKey("*"), (error, project_keys) ->
 			return callback(error) if error?
 			project_ids = RedisManager._extractIds project_keys
 			callback(error, project_ids)

	getAllDocIdsWithHistoryOps: (callback = (error, doc_ids) ->) ->
		# return all the docids, to find dangling history entries after
		# everything is flushed.
		rclient.keys rawUpdatesKey("*"), (error, doc_keys) ->
			return callback(error) if error?
			doc_ids = RedisManager._extractIds doc_keys
			callback(error, doc_ids)

	getDocIdsWithHistoryOps: (project_id, callback = (error, doc_ids) ->) ->
		rclient.smembers docsWithHistoryOpsKey(project_id), callback

	# iterate over keys asynchronously using redis scan (non-blocking)
	_getKeys: (pattern, callback) ->
		cursor = 0  # redis iterator
		keySet = {} # use hash to avoid duplicate results
		# scan over all keys looking for pattern
		doIteration = (cb) ->
			rclient.scan cursor, "MATCH", pattern, "COUNT", 1000, (error, reply) ->
				return callback(error) if error?
				[cursor, keys] = reply
				for key in keys
					keySet[key] = true
				if cursor == '0'  # note redis returns string result not numeric
					return callback(null, Object.keys(keySet))
				else
					doIteration()
		doIteration()

	# extract ids from keys like DocsWithHistoryOps:57fd0b1f53a8396d22b2c24b
	_extractIds: (keyList) ->
		ids = (key.split(":")[1] for key in keyList)
