From 5113c4f1983fa52cbe8db2f9d5c35698c0eadf8d Mon Sep 17 00:00:00 2001
From: michael <michael@freepascal.org>
Date: Sat, 23 Jun 2018 17:08:56 +0000
Subject: [PATCH] * Support OldValue

---
 packages/fcl-db/jsondataset.pas | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/packages/fcl-db/jsondataset.pas b/packages/fcl-db/jsondataset.pas
index dde33e7..bddc861 100644
--- a/packages/fcl-db/jsondataset.pas
+++ b/packages/fcl-db/jsondataset.pas
@@ -777,9 +777,19 @@ var
 
 begin
   if (FEditIdx=Buffer.Bookmark) then
-    R:=FEditRow
+    begin
+    if State=dsOldValue then
+      R:=Buffer.data
+    else
+      R:=FEditRow
+    end
   else
-    R:=Buffer.data;
+    begin
+    if State=dsOldValue then
+      Exit(Null)
+    else
+      R:=Buffer.data;
+    end;
   Result:=FFieldMapper.GetJSONDataForField(Field,R);
 end;