From bd762cb64b8755994b2d0fb90647321bcaaa0997 Mon Sep 17 00:00:00 2001
From: Echo Nolan <echo@echonolan.net>
Date: Mon, 27 Nov 2017 11:20:32 -0800
Subject: [PATCH 1/2] Allow Postgres migrations to enable extensions

---
 .../Database/Persist/Postgresql.hs                 | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/persistent-postgresql/Database/Persist/Postgresql.hs b/persistent-postgresql/Database/Persist/Postgresql.hs
index 933188f8c..fa9677618 100644
--- a/persistent-postgresql/Database/Persist/Postgresql.hs
+++ b/persistent-postgresql/Database/Persist/Postgresql.hs
@@ -4,6 +4,7 @@
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE ViewPatterns #-}
@@ -26,6 +27,7 @@ module Database.Persist.Postgresql
     , tableName
     , fieldName
     , mockMigration
+    , migrateEnableExtension
     ) where
 
 import Database.Persist.Sql
@@ -74,7 +76,7 @@ import Data.Aeson
 import Data.Aeson.Types (modifyFailure)
 import Control.Monad (forM)
 import Control.Monad.Trans.Reader (runReaderT)
-import Control.Monad.Trans.Writer (runWriterT)
+import Control.Monad.Trans.Writer (WriterT(..), runWriterT)
 import Data.Acquire (Acquire, mkAcquire, with)
 import System.Environment (getEnvironment)
 import Data.Int (Int64)
@@ -1178,3 +1180,13 @@ mockMigration mig = do
       result = runReaderT $ runWriterT $ runWriterT mig
   resp <- result sqlbackend
   mapM_ T.putStrLn $ map snd $ snd resp
+
+-- | Enable a Postgres extension. See https://www.postgresql.org/docs/10/static/contrib.html
+-- for a list.
+migrateEnableExtension :: Text -> Migration
+migrateEnableExtension extName = WriterT $ WriterT $ do
+  res :: [Single Int] <-
+    rawSql "SELECT COUNT(*) FROM pg_catalog.pg_extension WHERE extname = ?" [PersistText extName]
+  if res == [Single 0]
+    then return (((), []) , [(False, "CREATe EXTENSION \"" <> extName <> "\"")])
+    else return (((), []), [])

From 68e754abc39fa3e11a7d02af6caf868267b84db0 Mon Sep 17 00:00:00 2001
From: Echo Nolan <echo@echonolan.net>
Date: Fri, 22 Dec 2017 14:07:14 -0800
Subject: [PATCH 2/2] Update ChangeLog and set new version for Postgres library

---
 persistent-postgresql/ChangeLog.md                | 4 ++++
 persistent-postgresql/persistent-postgresql.cabal | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/persistent-postgresql/ChangeLog.md b/persistent-postgresql/ChangeLog.md
index d0f990d3c..d57322f52 100644
--- a/persistent-postgresql/ChangeLog.md
+++ b/persistent-postgresql/ChangeLog.md
@@ -1,3 +1,7 @@
+## 2.6.3
+
+* Added new function `migrateEnableExtension`, to enable Postgres extensions in migrations.
+
 ## 2.6.2.1
 
 * Fix bug where, if a custom column width was set, the field would be migrated every time [#742](https://github.com/yesodweb/persistent/pull/742)
diff --git a/persistent-postgresql/persistent-postgresql.cabal b/persistent-postgresql/persistent-postgresql.cabal
index a94884bf1..696edc67d 100644
--- a/persistent-postgresql/persistent-postgresql.cabal
+++ b/persistent-postgresql/persistent-postgresql.cabal
@@ -1,5 +1,5 @@
 name:            persistent-postgresql
-version:         2.6.2.1
+version:         2.6.3
 license:         MIT
 license-file:    LICENSE
 author:          Felipe Lessa, Michael Snoyman <michael@snoyman.com>