Fixed DataSync not generating the correct sql query for null conditions (#1359)

E.g. a condition like `where('field', null')` needs to add a SQL condition like `WHERE field IS NULL` instead of `WHERE field = NULL`

Author: mpscholten

IHP/DataSync/DynamicQuery.hs

@@ -63,6 +63,8 @@ data ConditionOperator
     | OpNotEqual -- ^ a <> b
     | OpAnd -- ^ a AND b
     | OpOr -- ^ a OR b
+    | OpIs -- ^ a IS b
+    | OpIsNot -- ^ a IS NOT b
     deriving (Show, Eq)
 
 data SelectedColumns

IHP/DataSync/DynamicQueryCompiler.hs

@@ -70,10 +70,19 @@ compileSelectedColumns (SelectSpecific fields) = PG.Many args
 compileCondition :: ConditionExpression -> (PG.Query, [PG.Action])
 compileCondition (ColumnExpression column) = ("?", [PG.toField $ PG.Identifier (fieldNameToColumnName column)])
 compileCondition NullExpression = ("NULL", [])
-compileCondition (InfixOperatorExpression a operator b) = ("(" <> queryA <> ") " <> compileOperator operator <> " (" <> queryB <> ")", paramsA <> paramsB)
+compileCondition (InfixOperatorExpression a OpEqual NullExpression) = compileCondition (InfixOperatorExpression a OpIs NullExpression) -- Turn 'a = NULL' into 'a IS NULL'
+compileCondition (InfixOperatorExpression a OpNotEqual NullExpression) = compileCondition (InfixOperatorExpression a OpIsNot NullExpression) -- Turn 'a <> NULL' into 'a IS NOT NULL'
+compileCondition (InfixOperatorExpression a operator b) = ("(" <> queryA <> ") " <> compileOperator operator <> " " <> rightOperand, paramsA <> paramsB)
     where
         (queryA, paramsA) = compileCondition a
         (queryB, paramsB) = compileCondition b
+
+        rightOperand = if rightParentheses
+                then "(" <>  queryB <> ")"
+                else queryB
+
+        rightParentheses :: Bool
+        rightParentheses = b /= NullExpression
 compileCondition (LiteralExpression literal) = ("?", [toValue literal])
     where
         toValue (IntValue int) = PG.toField int
@@ -93,4 +102,6 @@ compileOperator OpGreaterThanOrEqual = ">="
 compileOperator OpLessThanOrEqual = "<="
 compileOperator OpNotEqual = "<>"
 compileOperator OpAnd = "AND"
-compileOperator OpOr = "OR"
+compileOperator OpOr = "OR"
+compileOperator OpIs = "IS"
+compileOperator OpIsNot = "IS NOT"

Test/DataSync/DynamicQueryCompiler.hs

@@ -134,4 +134,34 @@ tests = do
                 compileQuery query `shouldBe`
                         ( "SELECT ? FROM ? WHERE (?) = (?) LIMIT ? OFFSET ?"
                         , [PG.Plain "*", PG.EscapeIdentifier "posts", PG.EscapeIdentifier "user_id", PG.Escape "b8553ce9-6a42-4a68-b5fc-259be3e2acdc", PG.Plain "25", PG.Plain "50"]
+                        )
+            
+            it "compile 'field = NULL' conditions to 'field IS NULL'" do
+                let query = DynamicSQLQuery
+                        { table = "posts"
+                        , selectedColumns = SelectAll
+                        , whereCondition = Just $ InfixOperatorExpression (ColumnExpression "userId") OpEqual NullExpression
+                        , orderByClause = []
+                        , limit = Nothing
+                        , offset = Nothing
+                        }
+                
+                compileQuery query `shouldBe`
+                        ( "SELECT ? FROM ? WHERE (?) IS NULL"
+                        , [PG.Plain "*", PG.EscapeIdentifier "posts", PG.EscapeIdentifier "user_id"]
+                        )
+
+            it "compile 'field <> NULL' conditions to 'field IS NOT NULL'" do
+                let query = DynamicSQLQuery
+                        { table = "posts"
+                        , selectedColumns = SelectAll
+                        , whereCondition = Just $ InfixOperatorExpression (ColumnExpression "userId") OpNotEqual NullExpression
+                        , orderByClause = []
+                        , limit = Nothing
+                        , offset = Nothing
+                        }
+                
+                compileQuery query `shouldBe`
+                        ( "SELECT ? FROM ? WHERE (?) IS NOT NULL"
+                        , [PG.Plain "*", PG.EscapeIdentifier "posts", PG.EscapeIdentifier "user_id"]
                         )