From 521871c476a83b0ae4e1dd4df7cc1722d046551d Mon Sep 17 00:00:00 2001
From: fr33domlover <fr33domlover@rel4tion.org>
Date: Tue, 2 Aug 2016 09:29:56 +0000
Subject: [PATCH] Refactor undirected edge SQL to remove repeated filter

---
 src/Database/Persist/Local/Sql.hs | 48 +++++++++++++++++++------------
 1 file changed, 30 insertions(+), 18 deletions(-)

diff --git a/src/Database/Persist/Local/Sql.hs b/src/Database/Persist/Local/Sql.hs
index a0fcfc6..2a1d4b8 100644
--- a/src/Database/Persist/Local/Sql.hs
+++ b/src/Database/Persist/Local/Sql.hs
@@ -169,6 +169,9 @@ infixr 5 ?++
 uedge :: DBName
 uedge = DBName "temp_undirected_edge_cte"
 
+ubase :: DBName
+ubase = DBName "temp_undirected_base_cte"
+
 temp :: DBName
 temp = DBName "temp_hierarchy_cte"
 
@@ -188,21 +191,30 @@ sqlUEdge
     :: (DBName -> Text) -> Text -> EntityDef -> FieldDef -> FieldDef -> Text
 sqlUEdge dbname filt tEdge bwd fwd =
     let t ^* f = dbname t <> "." <> dbname f
-    in  mconcat
-        [ dbname uedge
-        , " ("
-        , dbname $ fieldDB bwd, ", ", dbname $ fieldDB fwd
-        , ") AS (SELECT "
-            , entityDB tEdge ^* fieldDB bwd
-            , ", "
-            , entityDB tEdge ^* fieldDB fwd
-            , " FROM ", dbname $ entityDB tEdge
-            , filt
-        , " UNION ALL SELECT "
-            , entityDB tEdge ^* fieldDB fwd
-            , ", "
-            , entityDB tEdge ^* fieldDB bwd
-            , " FROM ", dbname $ entityDB tEdge
-            , filt
-        , ")"
-        ]
+        sqlBase = mconcat
+            [ dbname ubase
+            , " ("
+            , dbname $ fieldDB bwd, ", ", dbname $ fieldDB fwd
+            , ") AS (SELECT "
+                , entityDB tEdge ^* fieldDB bwd
+                , ", "
+                , entityDB tEdge ^* fieldDB fwd
+                , " FROM ", dbname $ entityDB tEdge
+                , filt
+            , "), "
+            ]
+        sqlEdge base = mconcat
+            [ dbname uedge
+            , " ("
+            , dbname $ fieldDB bwd, ", ", dbname $ fieldDB fwd
+            , ") AS (SELECT "
+                , base ^* fieldDB bwd, ", ", base ^* fieldDB fwd
+                , " FROM ", dbname base
+            , " UNION ALL SELECT "
+                , base ^* fieldDB fwd, ", ", base ^* fieldDB bwd
+                , " FROM ", dbname base
+            , ")"
+            ]
+    in  if T.null filt
+            then sqlEdge $ entityDB tEdge
+            else sqlBase <> sqlEdge ubase