Implements query counting in proc call and adds Content-Rage to response

headers in /rpc calls.

src/PostgREST/App.hs

@@ -73,7 +73,7 @@ app dbStructure conf reqBody req =
         Right (q, cq) -> do
           let singular = iPreferSingular apiRequest
               stm = createReadStatement q cq range singular
-                    (iPreferCount apiRequest) (contentType == TextCSV)
+                    shouldCount (contentType == TextCSV)
           respondToRange $ do
             row <- H.query () stm
             let (tableTotal, queryTotal, _ , body) = row
@@ -82,10 +82,7 @@ app dbStructure conf reqBody req =
               then responseLBS status404 [] ""
               else responseLBS status200 [contentTypeH] (cs body)
             else do
-              let frm = rangeOffset range
-                  to = frm + toInteger queryTotal - 1
-                  contentRange = contentRangeH frm to (toInteger <$> tableTotal)
-                  status = rangeStatus frm to (toInteger <$> tableTotal)
+              let (status, contentRange) = rangeHeader queryTotal tableTotal
                   canonical = urlEncodeVars -- should this be moved to the dbStructure (location)?
                     . sortBy (comparing fst)
                     . map (join (***) cs)
@@ -163,11 +160,13 @@ app dbStructure conf reqBody req =
           let p = V.head payload
               jwtSecret = configJwtSecret conf
           respondToRange $ do
-            bodyJson <- H.query () (callProc qi p range)
+            row <- H.query () (callProc qi p range shouldCount)
             returnJWT <- H.query qi doesProcReturnJWT
-            return $ responseLBS status200 [jsonH]
-                  (let body = fromMaybe emptyArray bodyJson in
-                      if returnJWT
+            let (tableTotal, queryTotal, body) = fromMaybe (Just 0, 0, emptyArray) row
+                (status, contentRange) = rangeHeader queryTotal tableTotal
+              in
+              return $ responseLBS status [jsonH, contentRange]
+                      (if returnJWT
                       then "{\"token\":\"" <> cs (tokenJWT jwtSecret body) <> "\"}"
                       else cs $ encode body)
         else return notFound
@@ -193,6 +192,7 @@ app dbStructure conf reqBody req =
   allOrigins = ("Access-Control-Allow-Origin", "*") :: Header
   schema = cs $ configSchema conf
   apiRequest = userApiRequest schema req reqBody
+  shouldCount = iPreferCount apiRequest
   range = restrictRange (configMaxRows conf) $ iRange apiRequest
   readDbRequest = DbRead <$> buildReadRequest (dbRelations dbStructure) apiRequest
   mutateDbRequest = DbMutate <$> buildMutateRequest apiRequest
@@ -204,6 +204,11 @@ app dbStructure conf reqBody req =
   respondToRange response = if range == emptyRange
                             then return $ errResponse status416 "HTTP Range error"
                             else response
+  rangeHeader queryTotal tableTotal = let frm = rangeOffset range
+                                          to = frm + toInteger queryTotal - 1
+                                          contentRange = contentRangeH frm to (toInteger <$> tableTotal)
+                                          status = rangeStatus frm to (toInteger <$> tableTotal)
+                                      in (status, contentRange)
 
 rangeStatus :: Integer -> Integer -> Maybe Integer -> Status
 rangeStatus _ _ Nothing = status200

src/PostgREST/QueryBuilder.hs

@@ -203,18 +203,26 @@ addJoinConditions schema (Node (query, (n, r)) forest) =
     updatedForest = mapM (addJoinConditions schema) forest
     addCond query' con = query'{flt_=con ++ flt_ query'}
 
-callProc :: QualifiedIdentifier -> JSON.Object -> NonnegRange -> H.Query () (Maybe JSON.Value)
-callProc qi params range =
-  H.statement sql HE.unit decodeObj True
+type ProcResults = (Maybe Int64, Int64, JSON.Value)
+callProc :: QualifiedIdentifier -> JSON.Object -> NonnegRange -> Bool -> H.Query () (Maybe ProcResults)
+callProc qi params range countTotal =
+  H.statement sql HE.unit decodeProc True
   where
-    sql = [qc| SELECT array_to_json(
+    sql = [qc| SELECT
+              {countQuery} as countTotal,
+              {countResult} as countResult,
+              array_to_json(
                 coalesce(array_agg(row_to_json(t)), '\{}')
               )::character varying
-              from ({_callSql}) t |]
+              from (select * {_callSql} {limitF range}) t |]
     _args = intercalate "," $ map _assignment (HM.toList params)
     _assignment (n,v) = pgFmtIdent n <> ":=" <> insertableValue v
-    _callSql = [qc| select * from {fromQi qi}({_args}) {limitF range} |] :: BS.ByteString
-    decodeObj = HD.maybeRow (HD.value HD.json)
+    _callSql = [qc| from {fromQi qi}({_args}) |] :: BS.ByteString
+    countQuery = if countTotal then [qc| (select pg_catalog.count(1) {_callSql} c) |] else "null::bigint" :: BS.ByteString
+    countResult = "pg_catalog.count(t)" :: BS.ByteString
+    decodeProc = HD.maybeRow procRow
+    procRow = (,,) <$> HD.nullableValue HD.int8 <*> HD.value HD.int8
+                   <*> HD.value HD.json
 
 operators :: [(Text, SqlFragment)]
 operators = [