diff --git a/Database/Groundhog/Postgresql.hs b/Database/Groundhog/Postgresql.hs
--- a/Database/Groundhog/Postgresql.hs
+++ b/Database/Groundhog/Postgresql.hs
@@ -9,6 +9,7 @@
     , module Database.Groundhog.Generic.Sql.Functions
     , explicitType
     , castType
+    , distinctOn
     ) where
 
 import Database.Groundhog
@@ -42,7 +43,7 @@
 import Data.Function (on)
 import Data.Int (Int64)
 import Data.IORef
-import Data.List (groupBy, intercalate, stripPrefix)
+import Data.List (groupBy, intercalate, isPrefixOf, stripPrefix)
 import Data.Maybe (fromJust, fromMaybe, isJust)
 import Data.Monoid
 import Data.Pool
@@ -75,7 +76,7 @@
   insertByAll v = H.insertByAll renderConfig queryRaw' True v
   replace k v = H.replace renderConfig queryRaw' executeRaw' (insertIntoConstructorTable False) k v
   replaceBy k v = H.replaceBy renderConfig executeRaw' k v
-  select options = H.select renderConfig queryRaw' "" options
+  select options = H.select renderConfig queryRaw' preColumns "" options
   selectAll = H.selectAll renderConfig queryRaw'
   get k = H.get renderConfig queryRaw' k
   getBy k = H.getBy renderConfig queryRaw' k
@@ -85,7 +86,7 @@
   deleteAll v = H.deleteAll renderConfig executeRaw' v
   count cond = H.count renderConfig queryRaw' cond
   countAll fakeV = H.countAll renderConfig queryRaw' fakeV
-  project p options = H.project renderConfig queryRaw' "" p options
+  project p options = H.project renderConfig queryRaw' preColumns "" p options
   migrate fakeV = migrate' fakeV
 
   executeRaw _ query ps = executeRaw' (fromString query) ps
@@ -96,6 +97,7 @@
 
 instance (MonadBaseControl IO m, MonadIO m, MonadLogger m) => SchemaAnalyzer (DbPersist Postgresql m) where
   schemaExists schema = queryRaw' "SELECT 1 FROM information_schema.schemata WHERE schema_name=?" [toPrimitivePersistValue proxy schema] (fmap isJust)
+  getCurrentSchema = queryRaw' "SELECT current_schema()" [] (fmap (>>= fst . fromPurePersistValues proxy))
   listTables schema = queryRaw' "SELECT table_name FROM information_schema.tables WHERE table_schema=coalesce(?,current_schema())" [toPrimitivePersistValue proxy schema] (mapAllRows $ return . fst . fromPurePersistValues proxy)
   listTableTriggers schema name = queryRaw' "SELECT trigger_name FROM information_schema.triggers WHERE event_object_schema=coalesce(?,current_schema()) AND event_object_table=?" [toPrimitivePersistValue proxy schema, toPrimitivePersistValue proxy name] (mapAllRows $ return . fst . fromPurePersistValues proxy)
   analyzeTable = analyzeTable'
@@ -207,13 +209,15 @@
 
 insertIntoConstructorTable :: Bool -> Bool -> Utf8 -> ConstructorDef -> [PersistValue] -> RenderS db r
 insertIntoConstructorTable withRet withId tName c vals = RenderS query vals' where
-  query = "INSERT INTO " <> tName <> "(" <> fieldNames <> ")VALUES(" <> placeholders <> ")" <> returning
+  query = "INSERT INTO " <> tName <> columnsValues <> returning
   (fields, returning) = case constrAutoKeyName c of
     Just idName -> (fields', returning') where
       fields' = if withId then (idName, dbType (0 :: Int64)):constrParams c else constrParams c
-      returning' = if withRet then "RETURNING(" <> escapeS (fromString idName) <> ")" else mempty
+      returning' = if withRet then " RETURNING(" <> escapeS (fromString idName) <> ")" else mempty
     _           -> (constrParams c, mempty)
-  fieldNames   = renderFields escapeS fields
+  columnsValues = case foldr (flatten escapeS) [] fields of
+    [] -> " DEFAULT VALUES"
+    xs -> "(" <> commasJoin xs <> ") VALUES(" <> placeholders <> ")"
   RenderS placeholders vals' = commasJoin $ map renderPersistValue vals
 
 insertList' :: forall m a.(MonadBaseControl IO m, MonadIO m, MonadLogger m, PersistField a) => [a] -> DbPersist Postgresql m Int64
@@ -274,9 +278,8 @@
 
 migrate' :: (PersistEntity v, MonadBaseControl IO m, MonadIO m, MonadLogger m) => v -> Migration (DbPersist Postgresql m)
 migrate' v = do
-  x <- lift $ queryRaw' "SELECT current_schema()" [] id
-  let schema = fst $ fromPurePersistValues proxy $ fromJust x
-      migPack = migrationPack schema
+  schema <- lift getCurrentSchema
+  let migPack = migrationPack $ fromJust schema
   migrateRecursively (migrateSchema migPack) (migrateEntity migPack) (migrateList migPack) v
 
 migrationPack :: (MonadBaseControl IO m, MonadIO m, MonadLogger m) => String -> GM.MigrationPack (DbPersist Postgresql m)
@@ -372,7 +375,6 @@
   table <- queryRaw' "SELECT * FROM information_schema.tables WHERE table_schema = coalesce(?, current_schema()) AND table_name = ?" [toPrimitivePersistValue proxy schema, toPrimitivePersistValue proxy name] id
   case table of
     Just _ -> do
-      -- omit primary keys
       let colQuery = "SELECT c.column_name, c.is_nullable, c.udt_name, c.column_default, c.character_maximum_length, c.numeric_precision, c.numeric_scale, c.datetime_precision, c.interval_type, a.attndims AS array_dims, te.typname AS array_elem\
 \  FROM pg_catalog.pg_attribute a\
 \  INNER JOIN pg_catalog.pg_class cl ON cl.oid = a.attrelid\
@@ -390,7 +392,10 @@
       uniqPrimary <- queryRaw' constraintQuery [toPrimitivePersistValue proxy ("PRIMARY KEY" :: String), toPrimitivePersistValue proxy schema, toPrimitivePersistValue proxy name] (mapAllRows $ return . fst . fromPurePersistValues proxy)
       uniqIndexes <- queryRaw' "SELECT ic.relname, a.attname FROM pg_catalog.pg_attribute a INNER JOIN pg_catalog.pg_class ic ON ic.oid = a.attrelid INNER JOIN pg_catalog.pg_index i ON i.indexrelid = ic.oid INNER JOIN pg_catalog.pg_class tc ON i.indrelid = tc.oid INNER JOIN pg_namespace sch ON sch.oid = tc.relnamespace WHERE sch.nspname = coalesce(?, current_schema()) AND tc.relname = ? AND a.attnum > 0 AND NOT a.attisdropped AND ic.oid NOT IN (SELECT conindid FROM pg_catalog.pg_constraint) AND NOT i.indisprimary AND i.indisunique ORDER BY ic.relname, a.attnum" [toPrimitivePersistValue proxy schema, toPrimitivePersistValue proxy name] (mapAllRows $ return . fst . fromPurePersistValues proxy)
       let mkUniqs typ = map (\us -> UniqueDef' (fst $ head us) typ (map snd us)) . groupBy ((==) `on` fst)
-      let uniqs = mkUniqs UniqueConstraint uniqConstraints ++ mkUniqs UniqueIndex uniqIndexes ++ mkUniqs UniquePrimary uniqPrimary
+          isAutoincremented = case filter (\c -> colName c `elem` map snd uniqPrimary) cols of
+                                [c] -> colType c `elem` [DbInt32, DbInt64] && maybe False ("nextval" `isPrefixOf`) (colDefault c)
+                                _ -> False
+      let uniqs = mkUniqs UniqueConstraint uniqConstraints ++ mkUniqs UniqueIndex uniqIndexes ++ mkUniqs (UniquePrimary isAutoincremented) uniqPrimary
       references <- analyzeTableReferences schema name
       return $ Just $ TableInfo cols uniqs references
     Nothing -> return Nothing
@@ -471,7 +476,7 @@
   , intercalate "," $ map escape cols
   , ")"
   ])]
-showAlterTable table (AddUnique (UniqueDef' uName UniquePrimary cols)) = [(False, defaultPriority, concat
+showAlterTable table (AddUnique (UniqueDef' uName (UniquePrimary _) cols)) = [(False, defaultPriority, concat
   [ "ALTER TABLE "
   , table
   , " ADD"
@@ -600,9 +605,7 @@
   DbAutoKey -> showSqlType DbInt64
 
 compareUniqs :: UniqueDef' -> UniqueDef' -> Bool
-compareUniqs (UniqueDef' _ UniquePrimary cols1) (UniqueDef' _ UniquePrimary cols2) = haveSameElems (==) cols1 cols2
--- only one of the uniques is primary
-compareUniqs (UniqueDef' _ type1 _) (UniqueDef' _ type2 _) | UniquePrimary `elem` [type1, type2] = False
+compareUniqs (UniqueDef' _ (UniquePrimary _) cols1) (UniqueDef' _ (UniquePrimary _) cols2) = haveSameElems (==) cols1 cols2
 compareUniqs (UniqueDef' name1 type1 cols1) (UniqueDef' name2 type2 cols2) = fromMaybe True (liftM2 (==) name1 name2) && type1 == type2 && haveSameElems (==) cols1 cols2
 
 compareRefs :: String -> (Maybe String, Reference) -> (Maybe String, Reference) -> Bool
@@ -765,3 +768,17 @@
 -- | Casts expression to a type. @castType value \"INT\"@ results in @value::INT@.
 castType :: Expression Postgresql r a => a -> String -> Expr Postgresql r a
 castType a t = mkExpr $ Snippet $ \conf _ -> ["(" <> renderExpr conf (toExpr a) <> ")::" <> fromString t] where
+
+-- | Distinct only on certain fields or expressions. For example, @select $ CondEmpty `distinctOn` (lower EmailField, IpField)@.
+distinctOn :: (db ~ Postgresql, HasSelectOptions a db r, HasDistinct a ~ HFalse, Projection' p db r p') => a -> p -> SelectOptions db r (HasLimit a) (HasOffset a) (HasOrder a) HTrue
+distinctOn opts p = opts' {dbSpecificOptions = ("DISTINCT_ON", clause): dbSpecificOptions opts'} where
+  opts' = getSelectOptions opts
+  clause = Snippet $ \conf _ -> [commasJoin $ concatMap (renderExprExtended conf 0) $ projectionExprs p []]
+
+preColumns :: HasSelectOptions opts Postgresql r => opts -> RenderS Postgresql r
+preColumns opts = clause where
+  clause = apply "DISTINCT_ON" (\t -> "DISTINCT ON (" <> t <> ")")
+  apply k f = case lookup k opts' of
+    Nothing -> mempty
+    Just (Snippet snippet) -> f $ head $ snippet renderConfig 0
+  opts' = dbSpecificOptions $ getSelectOptions opts
diff --git a/changelog b/changelog
--- a/changelog
+++ b/changelog
@@ -1,3 +1,7 @@
+0.5.1
+* DISTINCT ON select option
+* Add getCurrentSchema function into SchemaAnalyzer
+
 0.5.0
 * Simplified Geometry and Array function type signatures
 * Compatibility with GHC 7.8
diff --git a/groundhog-postgresql.cabal b/groundhog-postgresql.cabal
--- a/groundhog-postgresql.cabal
+++ b/groundhog-postgresql.cabal
@@ -1,5 +1,5 @@
 name:            groundhog-postgresql
-version:         0.5.0
+version:         0.5.1
 license:         BSD3
 license-file:    LICENSE
 author:          Boris Lykah <lykahb@gmail.com>
@@ -15,20 +15,20 @@
     changelog
 
 library
-    build-depends:   base                    >= 4         && < 5
-                   , postgresql-simple       >= 0.3       && < 0.5
-                   , postgresql-libpq        >= 0.6.1
-                   , bytestring              >= 0.9
-                   , blaze-builder           >= 0.3.0.0
-                   , transformers            >= 0.2.1
-                   , groundhog               >= 0.5.0     && < 0.6.0
-                   , monad-control           >= 0.3
-                   , monad-logger            >= 0.3
-                   , containers              >= 0.2
-                   , text                    >= 0.8
-                   , attoparsec              >= 0.8.5.3
-                   , resource-pool           >= 0.2.1
-                   , time                    >= 1.1
+    build-depends:   base                     >= 4         && < 5
+                   , postgresql-simple        >= 0.3       && < 0.5
+                   , postgresql-libpq         >= 0.6.1
+                   , bytestring               >= 0.9
+                   , blaze-builder            >= 0.3.0.0   && < 0.4
+                   , transformers             >= 0.2.1     && < 0.5
+                   , groundhog                >= 0.5.0     && < 0.6.0
+                   , monad-control            >= 0.3       && < 0.4
+                   , monad-logger             >= 0.3
+                   , containers               >= 0.2
+                   , text                     >= 0.8
+                   , attoparsec               >= 0.8.5.3
+                   , resource-pool            >= 0.2.1
+                   , time                     >= 1.1
     exposed-modules: Database.Groundhog.Postgresql
                      Database.Groundhog.Postgresql.Array
                      Database.Groundhog.Postgresql.Geometry