feat: allow not_null value for the is operator

src/PostgREST/ApiRequest/QueryParams.hs

@@ -46,7 +46,7 @@ import PostgREST.SchemaCache.Identifiers (FieldName)
 import PostgREST.ApiRequest.Types (AggregateFunction (..),
                                    EmbedParam (..), EmbedPath, Field,
                                    Filter (..), FtsOperator (..),
-                                   Hint, JoinType (..),
+                                   Hint, IsVal (..), JoinType (..),
                                    JsonOperand (..),
                                    JsonOperation (..), JsonPath,
                                    ListVal, LogicOperator (..),
@@ -56,8 +56,7 @@ import PostgREST.ApiRequest.Types (AggregateFunction (..),
                                    OrderNulls (..), OrderTerm (..),
                                    QPError (..), QuantOperator (..),
                                    SelectItem (..),
-                                   SimpleOperator (..), SingleVal,
-                                   TrileanVal (..))
+                                   SimpleOperator (..), SingleVal)
 
 import Protolude hiding (Sum, try)
 
@@ -640,7 +639,7 @@ pOpExpr pSVal = do
     pOperation = pIn <|> pIs <|> pIsDist <|> try pFts <|> try pSimpleOp <|> try pQuantOp <?> "operator (eq, gt, ...)"
 
     pIn = In <$> (try (string "in" *> pDelimiter) *> pListVal)
-    pIs = Is <$> (try (string "is" *> pDelimiter) *> pTriVal)
+    pIs = Is <$> (try (string "is" *> pDelimiter) *> pIsVal)
 
     pIsDist = IsDistinctFrom <$> (try (string "isdistinct" *> pDelimiter) *> pSVal)
 
@@ -653,11 +652,12 @@ pOpExpr pSVal = do
       quant <- optionMaybe $ try (between (char '(') (char ')') (try (string "any" $> QuantAny) <|> string "all" $> QuantAll))
       pDelimiter *> (OpQuant op quant <$> pSVal)
 
-    pTriVal = try (ciString "null"    $> TriNull)
-          <|> try (ciString "unknown" $> TriUnknown)
-          <|> try (ciString "true"    $> TriTrue)
-          <|> try (ciString "false"   $> TriFalse)
-          <?> "null or trilean value (unknown, true, false)"
+    pIsVal =  try (ciString "null"     $> IsNull)
+          <|> try (ciString "not_null" $> IsNotNull)
+          <|> try (ciString "true"     $> IsTriTrue)
+          <|> try (ciString "false"    $> IsTriFalse)
+          <|> try (ciString "unknown"  $> IsTriUnknown)
+          <?> "isVal: (null, not_null, true, false, unknown)"
 
     pFts = do
       op <-  try (string "fts"   $> FilterFts)

src/PostgREST/ApiRequest/Types.hs

@@ -28,7 +28,7 @@ module PostgREST.ApiRequest.Types
   , RaiseError(..)
   , RangeError(..)
   , SingleVal
-  , TrileanVal(..)
+  , IsVal(..)
   , SimpleOperator(..)
   , QuantOperator(..)
   , FtsOperator(..)
@@ -218,7 +218,7 @@ data Operation
   = Op SimpleOperator SingleVal
   | OpQuant QuantOperator (Maybe OpQuantifier) SingleVal
   | In ListVal
-  | Is TrileanVal
+  | Is IsVal
   | IsDistinctFrom SingleVal
   | Fts FtsOperator (Maybe Language) SingleVal
   deriving (Eq, Show)
@@ -231,12 +231,13 @@ type SingleVal = Text
 -- | Represents a list value in a filter, e.g. id=in.(val1,val2,val3)
 type ListVal = [Text]
 
--- | Three-valued logic values
-data TrileanVal
-  = TriTrue
-  | TriFalse
-  | TriNull
-  | TriUnknown
+data IsVal
+  = IsNull
+  | IsNotNull
+  -- Trilean values
+  | IsTriTrue
+  | IsTriFalse
+  | IsTriUnknown
   deriving (Eq, Show)
 
 -- Operators that are quantifiable, i.e. they can be used with the any/all modifiers

src/PostgREST/Plan.hs

@@ -795,8 +795,8 @@ addRelatedOrders (Node rp@ReadPlan{order,from} forest) = do
 --
 -- Setup:
 --
--- >>> let nullOp    = OpExpr True (Is TriNull)
--- >>> let nonNullOp = OpExpr False (Is TriNull)
+-- >>> let nullOp    = OpExpr True (Is IsNull)
+-- >>> let nonNullOp = OpExpr False (Is IsNull)
 -- >>> let notEqOp   = OpExpr True (Op OpNotEqual "val")
 -- >>> :{
 -- -- this represents the `projects(*)` part on `/clients?select=*,projects(*)`
@@ -847,7 +847,7 @@ addRelatedOrders (Node rp@ReadPlan{order,from} forest) = do
 -- Don't do anything to the filter if there's no embedding (a subtree) on projects. Assume it's a normal filter.
 --
 -- >>> ReadPlan.where_ . rootLabel <$> addNullEmbedFilters (readPlanTree nullOp [])
--- Right [CoercibleStmnt (CoercibleFilter {field = CoercibleField {cfName = "projects", cfJsonPath = [], cfToJson = False, cfIRType = "", cfTransform = Nothing, cfDefault = Nothing, cfFullRow = False}, opExpr = OpExpr True (Is TriNull)})]
+-- Right [CoercibleStmnt (CoercibleFilter {field = CoercibleField {cfName = "projects", cfJsonPath = [], cfToJson = False, cfIRType = "", cfTransform = Nothing, cfDefault = Nothing, cfFullRow = False}, opExpr = OpExpr True (Is IsNull)})]
 --
 -- If there's an embedding on projects, then change the filter to use the internal aggregate name (`clients_projects_1`) so the filter can succeed later.
 --
@@ -869,7 +869,7 @@ addNullEmbedFilters (Node rp@ReadPlan{where_=curLogic} forest) = do
       flt@(CoercibleStmnt (CoercibleFilter (CoercibleField fld [] _ _ _ _ _) opExpr)) ->
         let foundRP = find (\ReadPlan{relName, relAlias} -> fld == fromMaybe relName relAlias) rPlans in
         case (foundRP, opExpr) of
-          (Just ReadPlan{relAggAlias}, OpExpr b (Is TriNull)) -> Right $ CoercibleStmnt $ CoercibleFilterNullEmbed b relAggAlias
+          (Just ReadPlan{relAggAlias}, OpExpr b (Is IsNull)) -> Right $ CoercibleStmnt $ CoercibleFilterNullEmbed b relAggAlias
           _                                                   -> Right flt
       flt@(CoercibleStmnt _) ->
         Right flt

src/PostgREST/Query/SqlFragment.hs

@@ -59,6 +59,7 @@ import NeatInterpolation (trimming)
 import PostgREST.ApiRequest.Types        (AggregateFunction (..),
                                           Alias, Cast,
                                           FtsOperator (..),
+                                          IsVal (..),
                                           JsonOperand (..),
                                           JsonOperation (..),
                                           JsonPath,
@@ -69,8 +70,7 @@ import PostgREST.ApiRequest.Types        (AggregateFunction (..),
                                           OrderDirection (..),
                                           OrderNulls (..),
                                           QuantOperator (..),
-                                          SimpleOperator (..),
-                                          TrileanVal (..))
+                                          SimpleOperator (..))
 import PostgREST.MediaType               (MTVndPlanFormat (..),
                                           MTVndPlanOption (..))
 import PostgREST.Plan.ReadPlan           (JoinCondition (..))
@@ -380,13 +380,15 @@ pgFmtFilter table (CoercibleFilter fld (OpExpr hasNot oper)) = notOp <> " " <> p
 
    -- IS cannot be prepared. `PREPARE boolplan AS SELECT * FROM projects where id IS $1` will give a syntax error.
    -- The above can be fixed by using `PREPARE boolplan AS SELECT * FROM projects where id IS NOT DISTINCT FROM $1;`
-   -- However that would not accept the TRUE/FALSE/NULL/UNKNOWN keywords. See: https://stackoverflow.com/questions/6133525/proper-way-to-set-preparedstatement-parameter-to-null-under-postgres.
+   -- However that would not accept the TRUE/FALSE/NULL/"NOT NULL"/UNKNOWN keywords. See: https://stackoverflow.com/questions/6133525/proper-way-to-set-preparedstatement-parameter-to-null-under-postgres.
    -- This is why `IS` operands are whitelisted at the Parsers.hs level
-   Is triVal -> " IS " <> case triVal of
-     TriTrue    -> "TRUE"
-     TriFalse   -> "FALSE"
-     TriNull    -> "NULL"
-     TriUnknown -> "UNKNOWN"
+   Is isVal -> " IS " <>
+      case isVal of
+        IsNull       -> "NULL"
+        IsNotNull    -> "NOT NULL"
+        IsTriTrue    -> "TRUE"
+        IsTriFalse   -> "FALSE"
+        IsTriUnknown -> "UNKNOWN"
 
    IsDistinctFrom val -> " IS DISTINCT FROM " <> unknownLiteral val