[GitHub] [couchdb] nickva commented on a change in pull request #2666: soft-deletion for database

[GitBox <gi...@apache.org>]

nickva commented on a change in pull request #2666: soft-deletion for database
URL: https://github.com/apache/couchdb/pull/2666#discussion_r400377646
 
 

 ##########
 File path: src/fabric/src/fabric2_fdb.erl
 ##########
 @@ -346,12 +351,97 @@ delete(#{} = Db) ->
     } = ensure_current(Db),
 
     DbKey = erlfdb_tuple:pack({?ALL_DBS, DbName}, LayerPrefix),
-    erlfdb:clear(Tx, DbKey),
-    erlfdb:clear_range_startswith(Tx, DbPrefix),
+    DoRecovery = fabric2_util:do_recovery(),
+    case DoRecovery of
+        true ->
+            Timestamp = list_to_binary(fabric2_util:iso8601_timestamp()),
+            DeletedDbKey = erlfdb_tuple:pack({?DELETED_DBS, DbName, Timestamp},
+                LayerPrefix),
+            case erlfdb:wait(erlfdb:get(Tx, DeletedDbKey)) of
+                not_found ->
+                    erlfdb:set(Tx, DeletedDbKey, DbPrefix),
+                    erlfdb:clear(Tx, DbKey);
+                _Val ->
+                    erlang:error({deleted_database_exists, DbName})
+            end;
+        false ->
+            erlfdb:clear(Tx, DbKey),
+            erlfdb:clear_range_startswith(Tx, DbPrefix)
+    end,
     bump_metadata_version(Tx),
     ok.
 
 
+deleted_dbs_info(#{} = Db0) ->
+    #{
+        name := DbName,
+        tx := Tx,
+        layer_prefix := LayerPrefix
+    } = ensure_current(Db0, false),
+
+    DeletedDbKey =  erlfdb_tuple:pack({?DELETED_DBS, DbName}, LayerPrefix),
+    DeletedDbs = erlfdb:wait(erlfdb:get_range_startswith(Tx, DeletedDbKey)),
+    lists:foldl(fun({DbKey, DbPrefix}, Acc) ->
+        DBInfo = get_info_wait(get_info_future(Tx, DbPrefix)),
+        {?DELETED_DBS, DbName, DeletedTS} =
+            erlfdb_tuple:unpack(DbKey, LayerPrefix),
+        [{DeletedTS, DBInfo}| Acc]
+    end, [], DeletedDbs).
+
+
+undelete(#{} = Db0, TgtDbName, TimeStamp) ->
+    #{
+        name := DbName,
+        tx := Tx,
+        layer_prefix := LayerPrefix
+    } = ensure_current(Db0, false),
+    DbKey = erlfdb_tuple:pack({?ALL_DBS, TgtDbName}, LayerPrefix),
+    case erlfdb:wait(erlfdb:get(Tx, DbKey)) of
+        Bin when is_binary(Bin) ->
+            {error, file_exists};
+        not_found ->
+            DeletedDbTupleKey = {
+                ?DELETED_DBS,
+                DbName,
+                TimeStamp
+            },
+            DeleteDbKey =  erlfdb_tuple:pack(DeletedDbTupleKey, LayerPrefix),
+            case erlfdb:wait(erlfdb:get(Tx, DeleteDbKey)) of
+                not_found ->
+                    erlang:error({not_found, invalid_timestamp});
+                DbPrefix ->
+                    erlfdb:set(Tx, DbKey, DbPrefix),
+                    erlfdb:clear(Tx, DeleteDbKey),
+                    bump_metadata_version(Tx),
+                    ok
+            end
+    end.
+
+
+delete_deleted(#{} = Db0, TimeStamp) ->
+    #{
+        name := DbName,
+        tx := Tx,
+        layer_prefix := LayerPrefix
+    } = ensure_current(Db0),
+
+    DeletedDbTupleKey = {
+        ?DELETED_DBS,
+        DbName,
+        TimeStamp
+    },
+    DeleteDbKey =  erlfdb_tuple:pack(DeletedDbTupleKey, LayerPrefix),
+    case erlfdb:wait(erlfdb:get(Tx, DeleteDbKey)) of
+        not_found ->
+            erlang:error({not_found});
+        DbPrefix ->
+            erlfdb:clear(Tx, DeleteDbKey),
+            erlfdb:clear_range_startswith(Tx, DbPrefix),
+            bump_metadata_version(Tx)
 
 Review comment:
   I think we're ok not bumping it here if we guarantee (let's have a test for it) that any soft deleted db handle will reopen. For that we need to bump the db version when we soft-delete and ensure that to hard deletion (snapshot removal) always goes through the soft-deletion path first.
   
   

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