Before starting a db transanction, refresh the db handle from the cachecheck-security-in-transaction

Previously, a stale db handle could be re-used across a few separate
transactions. That would result in the database getting re-opened before every
one of those operations.

To prevent that from happening, check the cache before the transaction starts,
and if there is a newer version of the db handle and use that.

1 files changed, 27 insertions, 5 deletions

diff --git a/src/fabric/src/fabric2_fdb.erl b/src/fabric/src/fabric2_fdb.erl
index 1392ccd0f..1e370be95 100644
--- a/src/fabric/src/fabric2_fdb.erl
+++ b/src/fabric/src/fabric2_fdb.erl
@@ -82,16 +82,17 @@ transactional(DbName, Options, Fun) when is_binary(DbName) ->
 
 transactional(#{tx := undefined} = Db, Fun) ->
     try
-        Reopen = maps:get(reopen, Db, false),
-        Db1 = maps:remove(reopen, Db),
+        Db1 = refresh(Db),
+        Reopen = maps:get(reopen, Db1, false),
+        Db2 = maps:remove(reopen, Db1),
         LayerPrefix = case Reopen of
             true -> undefined;
-            false -> maps:get(layer_prefix, Db1)
+            false -> maps:get(layer_prefix, Db2)
         end,
         do_transaction(fun(Tx) ->
             case Reopen of
-                true -> Fun(reopen(Db1#{tx => Tx}));
-                false -> Fun(Db1#{tx => Tx})
+                true -> Fun(reopen(Db2#{tx => Tx}));
+                false -> Fun(Db2#{tx => Tx})
             end
         end, LayerPrefix)
     catch throw:{?MODULE, reopen} ->
@@ -239,6 +240,27 @@ open(#{} = Db0, Options) ->
     load_validate_doc_funs(Db3).
 
 
+refresh(#{tx := undefined, name := DbName, md_version := OldVer} = Db) ->
+    case fabric2_server:fetch(DbName) of
+        % Relying on these assumptions about the `md_version` value:
+        %  - It is bumped every time `db_version` is bumped
+        %  - Is a versionstamp, so we can check which one is newer
+        %  - If it is `not_found`, it would sort less than a binary value
+        #{md_version := Ver} = Db1 when Ver > OldVer ->
+            Db1#{
+                db_options := maps:get(db_options, Db),
+                user_ctx := maps:get(user_ctx, Db),
+                security_fun := maps:get(security_fun, Db)
+            };
+        _ ->
+            Db
+    end;
+
+refresh(#{} = Db) ->
+    Db.
+
+
+
 reopen(#{} = OldDb) ->
     require_transaction(OldDb),
     #{