Idempotent snapshot handle setting
If a transaction handle is already a snapshot, make setting it a snapshot again
a no-op.
diff --git a/src/erlfdb.erl b/src/erlfdb.erl
index 56ea4f7..d2ddb1f 100644
--- a/src/erlfdb.erl
+++ b/src/erlfdb.erl
@@ -172,7 +172,10 @@
snapshot(?IS_TX = Tx) ->
- {erlfdb_snapshot, Tx}.
+ {erlfdb_snapshot, Tx};
+
+snapshot(?IS_SS = SS) ->
+ SS.
set_option(DbOrTx, Option) ->
@@ -318,7 +321,10 @@
get_ss(?IS_TX = Tx, Key) ->
- erlfdb_nif:transaction_get(Tx, Key, true).
+ erlfdb_nif:transaction_get(Tx, Key, true);
+
+get_ss(?IS_SS = SS, Key) ->
+ get_ss(?GET_TX(SS), Key).
get_key(?IS_DB = Db, Key) ->
diff --git a/test/erlfdb_04_snapshot_test.erl b/test/erlfdb_04_snapshot_test.erl
new file mode 100644
index 0000000..2db7779
--- /dev/null
+++ b/test/erlfdb_04_snapshot_test.erl
@@ -0,0 +1,44 @@
+% Licensed under the Apache License, Version 2.0 (the "License"); you may not
+% use this file except in compliance with the License. You may obtain a copy of
+% the License at
+%
+% http://www.apache.org/licenses/LICENSE-2.0
+%
+% Unless required by applicable law or agreed to in writing, software
+% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+% License for the specific language governing permissions and limitations under
+% the License.
+
+-module(erlfdb_04_snapshot_test).
+
+-include_lib("eunit/include/eunit.hrl").
+
+
+snapshot_from_tx_test() ->
+ Db = erlfdb_util:get_test_db(),
+ Key = gen(10),
+ Val = gen(10),
+ erlfdb:set(Db, Key, Val),
+ erlfdb:transactional(Db, fun(Tx) ->
+ ?assertEqual(Val, erlfdb:wait(erlfdb:get_ss(Tx, Key))),
+ Ss = erlfdb:snapshot(Tx),
+ ?assertEqual(Val, erlfdb:wait(erlfdb:get(Ss, Key)))
+ end).
+
+
+snapshot_from_a_snapshot_test() ->
+ Db = erlfdb_util:get_test_db(),
+ Key = gen(10),
+ Val = gen(10),
+ erlfdb:set(Db, Key, Val),
+ erlfdb:transactional(Db, fun(Tx) ->
+ Ss = erlfdb:snapshot(Tx),
+ ?assertEqual(Val, erlfdb:wait(erlfdb:get_ss(Ss, Key))),
+ Ss = erlfdb:snapshot(Ss)
+ end).
+
+
+gen(Size) when is_integer(Size), Size > 1 ->
+ RandBin = crypto:strong_rand_bytes(Size - 1),
+ <<0, RandBin/binary>>.
