Array utilities

squeal-postgresql/src/Squeal/PostgreSQL/Expression/Array.hs

@@ -37,6 +37,15 @@ module Squeal.PostgreSQL.Expression.Array
   , unnest
   , arrAny
   , arrAll
+  , arrayAppend
+  , arrayPrepend
+  , arrayCat
+  , arrayPosition
+  , arrayPositionBegins
+  , arrayPositions
+  , arrayRemoveNull
+  , arrayReplace
+  , trimArray
   ) where
 
 import Data.String
@@ -47,6 +56,7 @@ import qualified Generics.SOP as SOP
 
 import Squeal.PostgreSQL.Expression
 import Squeal.PostgreSQL.Expression.Logic
+import Squeal.PostgreSQL.Expression.Null
 import Squeal.PostgreSQL.Expression.Type
 import Squeal.PostgreSQL.Query.From.Set
 import Squeal.PostgreSQL.Render
@@ -240,3 +250,42 @@ arrAny
   -> Expression grp lat with db params from (null ('PGvararray ty2)) -- ^ array
   -> Condition grp lat with db params from
 arrAny x (?) xs = x ? (UnsafeExpression $ "ANY" <+> parenthesized (renderSQL xs))
+
+arrayAppend :: '[null ('PGvararray ty), ty] ---> null ('PGvararray ty)
+arrayAppend = unsafeFunctionN "array_append"
+
+arrayPrepend :: '[ty, null ('PGvararray ty)] ---> null ('PGvararray ty)
+arrayPrepend = unsafeFunctionN "array_prepend"
+
+arrayCat
+  :: '[null ('PGvararray ty), null ('PGvararray ty)]
+  ---> null ('PGvararray ty)
+arrayCat = unsafeFunctionN "array_cat"
+
+arrayPosition :: '[null ('PGvararray ty), ty] ---> 'Null 'PGint8
+arrayPosition = unsafeFunctionN "array_position"
+
+arrayPositionBegins
+  :: '[null ('PGvararray ty), ty, null 'PGint8] ---> 'Null 'PGint8
+arrayPositionBegins = unsafeFunctionN "array_position"
+
+arrayPositions
+  :: '[null ('PGvararray ty), ty]
+  ---> null ('PGvararray ('NotNull 'PGint8))
+arrayPositions = unsafeFunctionN "array_positions"
+
+arrayRemove :: '[null ('PGvararray ty), ty] ---> null ('PGvararray ty)
+arrayRemove = unsafeFunctionN "array_remove"
+
+arrayRemoveNull :: null ('PGvararray ('Null ty)) --> null ('PGvararray ('NotNull ty))
+arrayRemoveNull arr = UnsafeExpression (renderSQL (arrayRemove (arr *: null_)))
+
+arrayReplace
+  :: '[null ('PGvararray ty), ty, ty]
+  ---> null ('PGvararray ty)
+arrayReplace = unsafeFunctionN "array_replace"
+
+trimArray
+  :: '[null ('PGvararray ty), 'NotNull 'PGint8]
+  ---> null ('PGvararray ty)
+trimArray = unsafeFunctionN "trim_array"

squeal-postgresql/src/Squeal/PostgreSQL/Session/Decode.hs

@@ -43,6 +43,7 @@ module Squeal.PostgreSQL.Session.Decode
   , genericProductRow
   , appendRows
   , consRow
+  , ArrayField (..)
     -- * Decoding Classes
   , FromValue (..)
   , FromField (..)
@@ -540,6 +541,42 @@ instance {-# OVERLAPPABLE #-} IsLabel fld (MaybeT (DecodeRow row) y)
     fromLabel = MaybeT . decodeRow $ \(_ SOP.:* bs) ->
       runDecodeRow (runMaybeT (fromLabel @fld)) bs
 
+{- | Utility for decoding array fields in a `DecodeRow`,
+accessed via overloaded labels.
+-}
+newtype ArrayField row y = ArrayField
+  { runArrayField
+      :: StateT Strict.ByteString (Except Strict.Text) y
+      -> DecodeRow row [y]
+  }
+instance {-# OVERLAPPING #-}
+  ( KnownSymbol fld
+  , PG y ~ ty
+  , arr ~ 'NotNull ('PGvararray ('NotNull ty))
+  ) => IsLabel fld (ArrayField (fld ::: arr ': row) y) where
+    fromLabel = ArrayField $ \yval ->
+      decodeRow $ \(SOP.K bytesMaybe SOP.:* _) -> do
+        let
+          flderr = mconcat
+            [ "field name: "
+            , "\"", fromString (symbolVal (SOP.Proxy @fld)), "\"; "
+            ]
+          yarr
+            = devalue
+            . array
+            . dimensionArray replicateM
+            . valueArray
+            . revalue
+            $ yval
+        case bytesMaybe of
+          Nothing -> Left (flderr <> "encountered unexpected NULL")
+          Just bytes -> runExcept (evalStateT yarr bytes)
+instance {-# OVERLAPPABLE #-} IsLabel fld (ArrayField row y)
+  => IsLabel fld (ArrayField (field ': row) y) where
+    fromLabel = ArrayField $ \yval ->
+      decodeRow $ \(_ SOP.:* bytess) ->
+        runDecodeRow (runArrayField (fromLabel @fld) yval) bytess
+
 -- | A `GenericRow` constraint to ensure that a Haskell type
 -- is a record type,
 -- has a `RowPG`,