Add Preference-Applied header for POST upsert

- Ensure creating nothing on ignore-duplicates succeeds
- Refactor locationF query

src/PostgREST/ApiRequest.hs

@@ -116,8 +116,8 @@ userApiRequest schema req reqBody
       , iPreferRepresentation = representation
       , iPreferSingleObjectParameter = singleObject
       , iPreferCount = hasPrefer "count=exact"
-      , iPreferResolution = if hasPrefer "resolution=merge-duplicates" then Just MergeDuplicates
-                            else if hasPrefer "resolution=ignore-duplicates" then Just IgnoreDuplicates
+      , iPreferResolution = if hasPrefer (show MergeDuplicates) then Just MergeDuplicates
+                            else if hasPrefer (show IgnoreDuplicates) then Just IgnoreDuplicates
                             else Nothing
       , iFilters = filters
       , iLogic = [(toS k, toS $ fromJust v) | (k,v) <- qParams, isJust v, endingIn ["and", "or"] k ]

src/PostgREST/App.hs

@@ -157,10 +157,10 @@ app dbStructure proc conf apiRequest =
                  && iPreferRepresentation apiRequest == Full
                 then return $ singularityError (toInteger nRows)
                 else do
-                  let stm = createWriteStatement sq mq
+                  let pkCols = tablePKCols dbStructure tSchema tName
+                      stm = createWriteStatement sq mq
                         (contentType == CTSingularJSON) isSingle
-                        (contentType == CTTextCSV) (iPreferRepresentation apiRequest)
-                        (tablePKCols dbStructure tSchema tName)
+                        (contentType == CTTextCSV) (iPreferRepresentation apiRequest) pkCols
                   row <- H.query (toS pjRaw) stm
                   let (_, _, fs, body) = extractQueryResult row
                       headers = catMaybes [
@@ -172,6 +172,9 @@ app dbStructure proc conf apiRequest =
                             else Nothing
                         , Just . contentRangeH 1 0 $
                             toInteger <$> if shouldCount then Just nRows else Nothing
+                        , if null pkCols
+                            then Nothing
+                            else (\x -> ("Preference-Applied", show x)) <$> iPreferResolution apiRequest
                         ]
 
                   return . responseLBS status201 headers $

src/PostgREST/QueryBuilder.hs

@@ -121,7 +121,7 @@ createWriteStatement selectQuery mutateQuery wantSingle wantHdrs asCsv rep pKeys
       "'' AS total_result_set", -- when updateing it does not make sense
       "pg_catalog.count(_postgrest_t) AS page_total",
       if wantHdrs
-         then locationF pKeys
+         then "coalesce(" <> locationF pKeys <> ", " <> noLocationF <> ")"
          else noLocationF <> " AS header",
       if rep == Full
          then bodyF <> " AS body"
@@ -278,7 +278,7 @@ requestToQuery schema isParent (DbRead (Node (Select colSelects tbls logicForest
 requestToQuery schema _ (DbMutate (Insert mainTbl pkCols p@(PayloadJSON _ pType pKeys) onConflct logicForest returnings)) =
   unwords [
     ("WITH " <> ignoredBody) `emptyOnFalse` not payloadIsEmpty,
-    "INSERT INTO ", fromQi qi, if payloadIsEmpty then " " else "(" <> cols <> ") ",
+    "INSERT INTO ", fromQi qi, if payloadIsEmpty then " " else "(" <> cols <> ")",
     case (pType, payloadIsEmpty) of
       (PJArray _, True) -> "SELECT null WHERE false"
       (PJObject, True)  -> "DEFAULT VALUES"
@@ -369,16 +369,12 @@ asBinaryF :: FieldName -> SqlFragment
 asBinaryF fieldName = "coalesce(string_agg(_postgrest_t." <> pgFmtIdent fieldName <> ", ''), '')"
 
 locationF :: [Text] -> SqlFragment
-locationF pKeys =
-    "(" <>
-    " WITH s AS (SELECT row_to_json(ss) as r from " <> sourceCTEName <> " as ss  limit 1)" <>
-    " SELECT array_agg(json_data.key || '=' || coalesce('eq.' || json_data.value, 'is.null'))" <>
-    " FROM s, json_each_text(s.r) AS json_data" <>
-    (
-      if null pKeys
-      then ""
-      else " WHERE json_data.key IN ('" <> intercalate "','" pKeys <> "')"
-    ) <> ")"
+locationF pKeys = [qc|(
+  WITH data AS (SELECT row_to_json(_) AS row FROM {sourceCTEName} AS _ LIMIT 1)
+  SELECT array_agg(json_data.key || '=' || coalesce('eq.' || json_data.value, 'is.null'))
+  FROM data CROSS JOIN json_each_text(data.row) AS json_data
+  {("WHERE json_data.key IN ('" <> intercalate "','" pKeys <> "')") `emptyOnFalse` null pKeys}
+)|]
 
 limitF :: NonnegRange -> SqlFragment
 limitF r  = if r == allRange

src/PostgREST/Types.hs

@@ -26,7 +26,10 @@ data ApiRequestError = ActionInappropriate
                      | InvalidFilters
                      deriving (Show, Eq)
 
-data PreferResolution = MergeDuplicates | IgnoreDuplicates deriving (Eq, Show)
+data PreferResolution = MergeDuplicates | IgnoreDuplicates deriving Eq
+instance Show PreferResolution where
+  show MergeDuplicates  = "resolution=merge-duplicates"
+  show IgnoreDuplicates = "resolution=ignore-duplicates"
 
 data DbStructure = DbStructure {
   dbTables      :: [Table]