Export functionality for user-defined extensions

beam-postgres/ChangeLog.md

@@ -5,6 +5,8 @@
 * Added instances for `BeamSqlBackendIsString Postgres (CI String)` and
   `BeamSqlBackendIsString Postgres (CI Text)`, allowing the use of `toTsVector`
   over colums of type `citext` (#818)
+* Exposed the functionality to implement user-defined extensions via
+  `Database.Beam.Postgres.Extensions` (#819)
 
 ## Bug fixes
 
@@ -30,7 +32,7 @@
   role attribute and is the appropriate choice when the client and
   server are on different hosts — see
   `Database.Beam.Postgres.Extensions.Copy.Stream`.
-  
+
 ## Bug fixes
 
 * Fixed an issue where a window function applied over the result of `nub_` (or

beam-postgres/Database/Beam/Postgres/Extensions.hs

@@ -9,9 +9,29 @@
 -- the extension in a particular backend. @beam-postgres@ provides predicates
 -- and checks for @beam-migrate@ which allow extensions to be included as
 -- regular parts of beam migrations.
-module Database.Beam.Postgres.Extensions where
+module Database.Beam.Postgres.Extensions (
+  -- * Handling extensions
+  PgExtensionEntity,
+  getPgExtension,
+
+  -- * Defining extensions
+  IsPgExtension(..),
+  -- ** Helpers
+  PgExpr,
+  LiftPg,
+  funcE,
+
+  -- * Migrations
+  PgHasExtension(..),
+  pgCreateExtension,
+  pgDropExtension,
+  pgExtensionActionProvider,
+) where
 
 import           Database.Beam
+import           Database.Beam.Backend.SQL ( IsSql92ExpressionSyntax(..), IsSql92FieldNameSyntax(..),
+                                             IsSql99ExpressionSyntax, IsSql99FunctionExpressionSyntax(..)
+                                           )
 import           Database.Beam.Schema.Tables
 
 import           Database.Beam.Postgres.Types
@@ -121,6 +141,21 @@ getPgExtension :: DatabaseEntity Postgres db (PgExtensionEntity extension)
                -> extension
 getPgExtension (DatabaseEntity (PgDatabaseExtension _ ext)) = ext
 
+-- *** Helpers to write postgres user-defined extensions
+
+-- | @since 0.6.2.0
+type PgExpr ctxt s = QGenExpr ctxt Postgres s
+
+-- | @since 0.6.2.0
+type family LiftPg ctxt s fn where
+  LiftPg ctxt s (Maybe a -> b) = Maybe (PgExpr ctxt s a) -> LiftPg ctxt s b
+  LiftPg ctxt s (a -> b) = PgExpr ctxt s a -> LiftPg ctxt s b
+  LiftPg ctxt s a = PgExpr ctxt s a
+
+-- | @since 0.6.2.0
+funcE :: IsSql99ExpressionSyntax expr => Text -> [expr] -> expr
+funcE nm = functionCallE (fieldE (unqualifiedField nm))
+
 -- *** Migrations support for extensions
 
 -- | 'Migration' representing the Postgres @CREATE EXTENSION@ command. Because
@@ -191,3 +226,4 @@ pgDropExtensionProvider =
      pure (PotentialAction (HS.fromList [p extP]) mempty
                            (pure (MigrationCommand cmd MigrationKeepsData))
                            ("Unload the postgres extension " <> ext) 1)
+

beam-postgres/Database/Beam/Postgres/Extensions/UuidOssp.hs

@@ -10,8 +10,7 @@ import           Data.Text (Text)
 import           Data.UUID.Types (UUID)
 
 import           Database.Beam
-import           Database.Beam.Postgres.Extensions
-import           Database.Beam.Postgres.Extensions.Internal
+import           Database.Beam.Postgres.Extensions ( LiftPg, IsPgExtension(..), funcE )
 
 -- | Data type representing definitions contained in the @uuid-ossp@ extension
 data UuidOssp = UuidOssp

beam-postgres/Database/Beam/Postgres/PgCrypto.hs

@@ -9,8 +9,7 @@ module Database.Beam.Postgres.PgCrypto
 import Database.Beam
 import Database.Beam.Backend.SQL
 
-import Database.Beam.Postgres.Extensions
-import Database.Beam.Postgres.Extensions.Internal
+import Database.Beam.Postgres.Extensions( LiftPg, PgExpr, IsPgExtension(..), funcE )
 
 import Data.Int
 import Data.Text (Text)

beam-postgres/beam-postgres.cabal

@@ -23,16 +23,15 @@ library
                       Database.Beam.Postgres.Full
 
                       Database.Beam.Postgres.PgCrypto
+                      Database.Beam.Postgres.Extensions
                       Database.Beam.Postgres.Extensions.UuidOssp
 
                       Database.Beam.Postgres.TempTable
 
   other-modules:      Database.Beam.Postgres.Connection
                       Database.Beam.Postgres.Debug
-                      Database.Beam.Postgres.Extensions
                       Database.Beam.Postgres.Extensions.Copy.File
                       Database.Beam.Postgres.Extensions.Copy.Stream
-                      Database.Beam.Postgres.Extensions.Internal
                       Database.Beam.Postgres.PgSpecific
                       Database.Beam.Postgres.Types