better mapReduce apis

+ mapReduce is now the convience function that returns a cursor
+ runMapReduce can be called if you want the intermediate
  result meta-data
+ mapReduceResults will take the result meta-data and open a
  cursor on it
This commit is contained in:
Scott R. Parish 2010-03-08 19:42:47 -06:00
parent 0a391e631b
commit ece60d87ad

View file

@ -56,7 +56,10 @@ module Database.MongoDB
Direction(..),
createIndex, dropIndex, dropIndexes, indexInformation,
-- * Map-Reduce
MapReduceOpt(..), mapReduce,
MapReduceOpt(..),
mapReduce, mapReduceWScopes,
runMapReduce, runMapReduceWScopes,
mapReduceResults,
)
where
import Control.Exception
@ -653,18 +656,86 @@ mrOptToTuple (MROptFinalize f) = ("finalize", BsonJSCode f)
mrOptToTuple (MROptScope s) = ("scope", BsonDoc s)
mrOptToTuple MROptVerbose = ("verbose", BsonBool True)
mapReduce :: Connection -> FullCollection
-- | Issue a map/reduce command and return the results metadata. If
-- all you care about is the actual map/reduce results you might want
-- to use the 'mapReduce' command instead.
--
-- The results meta-document will look something like this:
--
-- > {"result": "tmp.mr.mapreduce_1268095152_14",
-- > "timeMillis": 67,
-- > "counts": {"input": 4,
-- > "emit": 6,
-- > "output": 3},
-- > "ok": 1.0}
--
-- The /results/ field is the collection name within the same Database
-- that contain the results of the map/reduce.
runMapReduce :: Connection -> FullCollection
-> JSCode -- ^ mapping javascript function
-> JSCode -- ^ reducing javascript function
-> [MapReduceOpt]
-> IO BsonDoc
mapReduce c fc m r opts = do
runMapReduce c fc m r opts = do
let (db, col) = splitFullCol fc
doc = [("mapreduce", toBson col),
("map", BsonCode m),
("reduce", BsonCode r)] ++ List.map mrOptToTuple opts
("map", BsonJSCode m),
("reduce", BsonJSCode r)] ++ List.map mrOptToTuple opts
runCommand c db $ toBsonDoc doc
-- | Issue a map/reduce command with associated scopes and return the
-- results metadata. If all you care about is the actual map/reduce
-- results you might want to use the 'mapReduce' command instead.
--
-- See 'runMapReduce' for more information about the form of the
-- result metadata.
runMapReduceWScopes :: Connection -> FullCollection
-> JSCode -- ^ mapping javascript function
-> BsonDoc -- ^ Scope for mapping function
-> JSCode -- ^ reducing javascript function
-> BsonDoc -- ^ Scope for reducing function
-> [MapReduceOpt]
-> IO BsonDoc
runMapReduceWScopes c fc m ms r rs opts = do
let (db, col) = splitFullCol fc
doc = [("mapreduce", toBson col),
("map", BsonJSCodeWScope m ms),
("reduce", BsonJSCodeWScope r rs)] ++ List.map mrOptToTuple opts
runCommand c db $ toBsonDoc doc
-- | Given a result metadata from a 'mapReduce' command (or
-- 'mapReduceWScope'), issue the 'find' command that will produce the
-- actual map/reduce results.
mapReduceResults :: Connection -> Database -> BsonDoc -> IO Cursor
mapReduceResults c db r = do
let col = case List.lookup (s2L "result") r of
Just bCol -> fromBson bCol
Nothing -> throwOpFailure "No 'result' in mapReduce response"
fc = L.append (L.append db $ s2L ".") col
find c fc []
-- | Run map/reduce and produce a cursor on the results.
mapReduce :: Connection -> FullCollection
-> JSCode -- ^ mapping javascript function
-> JSCode -- ^ reducing javascript function
-> [MapReduceOpt]
-> IO Cursor
mapReduce c fc m r opts =
runMapReduce c fc m r opts >>= mapReduceResults c (fst $ splitFullCol fc)
-- | Run map/reduce with associated scopes and produce a cursor on the
-- results.
mapReduceWScopes :: Connection -> FullCollection
-> JSCode -- ^ mapping javascript function
-> BsonDoc -- ^ Scope for mapping function
-> JSCode -- ^ reducing javascript function
-> BsonDoc -- ^ Scope for mapping function
-> [MapReduceOpt]
-> IO Cursor
mapReduceWScopes c fc m ms r rs opts =
runMapReduceWScopes c fc m ms r rs opts >>=
mapReduceResults c (fst $ splitFullCol fc)
-- | Conveniently stores the /BsonDoc/ to the /FullCollection/
-- if there is an _id present in the /BsonDoc/ then it already has
-- a place in the DB, so we update it using the _id, otherwise