Merge pull request #96 from harporoeder/master

Add unsafeSqlCastAs

src/Database/Esqueleto/Internal/Sql.hs

@@ -33,6 +33,7 @@ module Database.Esqueleto.Internal.Sql
   , unsafeSqlBinOp
   , unsafeSqlBinOpComposite
   , unsafeSqlValue
+  , unsafeSqlCastAs
   , unsafeSqlFunction
   , unsafeSqlExtractSubField
   , UnsafeSqlFunctionArgument
@@ -101,6 +102,7 @@ data CompositeKeyError =
   | FoldHelpError
   | SqlCaseError
   | SqlBinOpError
+  | SqlCastAsError
   | MakeOnClauseError
   | MakeExcError
   | MakeSetError
@@ -765,6 +767,14 @@ unsafeSqlFunctionParens name arg =
           uncommas' $ map (\(ERaw p f) -> first (parensM p) (f info)) $ toArgList arg
     in (name <> parens argsTLB, argsVals)
 
+-- | (Internal) An explicit SQL type cast using CAST(value as type).
+-- See 'unsafeSqlBinOp' for warnings.
+unsafeSqlCastAs :: T.Text -> SqlExpr (Value a) -> SqlExpr (Value b)
+unsafeSqlCastAs t (ERaw p f) =
+  ERaw Never $ \info ->
+    let (b, v) = f info
+    in ("CAST" <> parens ( parensM p b <> " AS " <> TLB.fromText t), v )
+unsafeSqlCastAs _ (ECompositeKey _) = throw (CompositeKeyErr SqlCastAsError)
 
 class UnsafeSqlFunctionArgument a where
   toArgList :: a -> [SqlExpr (Value ())]