From 9c695533733e59bc83fc6175a6fc9288936db54e Mon Sep 17 00:00:00 2001
From: Diogo Biazus <diogob@gmail.com>
Date: Thu, 25 Jun 2015 12:15:00 -0400
Subject: [PATCH] Verifies PostgreSQL version is supported (+9.2) before
 spawning server [fixes #157]

---
 src/PostgREST/Main.hs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/PostgREST/Main.hs b/src/PostgREST/Main.hs
index 22fa11dde..58cd0ea07 100644
--- a/src/PostgREST/Main.hs
+++ b/src/PostgREST/Main.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE QuasiQuotes, ScopedTypeVariables #-}
 module Main where
 
 import Paths_postgrest (version)
@@ -17,12 +18,18 @@ import Network.Wai.Middleware.Static (staticPolicy, only)
 import Network.Wai.Middleware.RequestLogger (logStdout)
 import Data.List (intercalate)
 import Data.Version (versionBranch)
+import Data.Functor.Identity
+import Data.Text(Text)
 import qualified Hasql as H
 import qualified Hasql.Postgres as P
 import Options.Applicative hiding (columns)
 
 import PostgREST.Config (AppConfig(..), argParser, corsPolicy)
 
+isServerVersionSupported = do
+  Identity (row :: Text) <- H.tx Nothing $ H.singleEx $ [H.stmt|SHOW server_version_num|]
+  return $ read (cs row) >= 90200
+
 main :: IO ()
 main = do
   let opts = info (helper <*> argParser) $
@@ -61,6 +68,9 @@ main = do
   pool :: H.Pool P.Postgres
           <- H.acquirePool pgSettings poolSettings
 
+  resOrError <- H.session pool isServerVersionSupported
+  either (fail . show) (\supported -> unless supported $ fail "Cannot run in this PostgreSQL version, PostgREST needs at least 9.2.0") resOrError
+
   runSettings appSettings $ middle $ \req respond -> do
     body <- strictRequestBody req
     resOrError <- liftIO $ H.session pool $ H.tx Nothing $