Add aggregate functions (#2925)

The aggregate functions SUM(), MAX(), MIN(), AVG(), and COUNT() are now supported.

src/PostgREST/Plan/ReadPlan.hs

@@ -6,11 +6,12 @@ module PostgREST.Plan.ReadPlan
 
 import Data.Tree (Tree (..))
 
-import PostgREST.ApiRequest.Types         (Alias, Cast, Depth, Hint,
+import PostgREST.ApiRequest.Types         (Alias, Depth, Hint,
                                            JoinType, NodeName)
-import PostgREST.Plan.Types               (CoercibleField (..),
-                                           CoercibleLogicTree,
-                                           CoercibleOrderTerm)
+import PostgREST.Plan.Types               (CoercibleLogicTree,
+                                           CoercibleOrderTerm,
+                                           CoercibleSelectField (..),
+                                           RelSelectField (..))
 import PostgREST.RangeQuery               (NonnegRange)
 import PostgREST.SchemaCache.Identifiers  (FieldName,
                                            QualifiedIdentifier)
@@ -28,7 +29,7 @@ data JoinCondition =
   deriving (Eq, Show)
 
 data ReadPlan = ReadPlan
-  { select       :: [(CoercibleField, Maybe Cast, Maybe Alias)]
+  { select       :: [CoercibleSelectField]
   , from         :: QualifiedIdentifier
   , fromAlias    :: Maybe Alias
   , where_       :: [CoercibleLogicTree]
@@ -42,6 +43,7 @@ data ReadPlan = ReadPlan
   , relHint      :: Maybe Hint
   , relJoinType  :: Maybe JoinType
   , relIsSpread  :: Bool
+  , relSelect    :: [RelSelectField]
   , depth        :: Depth
   -- ^ used for aliasing
   }

src/PostgREST/Plan/Types.hs

@@ -1,13 +1,18 @@
 module PostgREST.Plan.Types
   ( CoercibleField(..)
+  , CoercibleSelectField(..)
   , unknownField
   , CoercibleLogicTree(..)
   , CoercibleFilter(..)
   , TransformerProc
   , CoercibleOrderTerm(..)
+  , RelSelectField(..)
+  , RelJsonEmbedMode(..)
+  , SpreadSelectField(..)
   ) where
 
-import PostgREST.ApiRequest.Types (Field, JsonPath, LogicOperator,
+import PostgREST.ApiRequest.Types (AggregateFunction, Alias, Cast,
+                                   Field, JsonPath, LogicOperator,
                                    OpExpr, OrderDirection, OrderNulls)
 
 import PostgREST.SchemaCache.Identifiers (FieldName)
@@ -65,3 +70,37 @@ data CoercibleOrderTerm
     , coNullOrder :: Maybe OrderNulls
     }
   deriving (Eq, Show)
+
+data CoercibleSelectField = CoercibleSelectField
+  { csField       :: CoercibleField
+  , csAggFunction :: Maybe AggregateFunction
+  , csAggCast     :: Maybe Cast
+  , csCast        :: Maybe Cast
+  , csAlias       :: Maybe Alias
+  }
+  deriving (Eq, Show)
+
+data RelJsonEmbedMode = JsonObject | JsonArray
+  deriving (Show, Eq)
+
+data RelSelectField
+  = JsonEmbed
+      { rsSelName    :: FieldName
+      , rsAggAlias   :: Alias
+      , rsEmbedMode  :: RelJsonEmbedMode
+      , rsEmptyEmbed :: Bool
+      }
+  | Spread
+      { rsSpreadSel :: [SpreadSelectField]
+      , rsAggAlias  :: Alias
+      }
+  deriving (Eq, Show)
+
+data SpreadSelectField =
+  SpreadSelectField
+  { ssSelName        :: FieldName
+  , ssSelAggFunction :: Maybe AggregateFunction
+  , ssSelAggCast     :: Maybe Cast
+  , ssSelAlias       :: Maybe Alias
+  }
+  deriving (Eq, Show)