os: KeyValueDB: implement snapshot iterators

Create a set of functions, to be implemented by derivative classes of
KeyValueDB, responsible for returning an iterator with strong
read-consistency guarantees. How this iterator is implemented, or by what
is it backed up, is implementation specific, but it must guarantee that
all reads made using this iterator are as if there were no subsequent
writes to the store since we created the iterator.

For instance, LevelDBStore will back this iterator with a leveldb Snapshot,
while KeyValueDBMemory will perform a copy of its in-memory map.

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/test/ObjectMap/KeyValueDBMemory.h b/src/test/ObjectMap/KeyValueDBMemory.h
index c7bb2878238..baed9de28e0 100644
--- a/src/test/ObjectMap/KeyValueDBMemory.h
+++ b/src/test/ObjectMap/KeyValueDBMemory.h
@@ -138,4 +138,5 @@ private:
 
 protected:
   WholeSpaceIterator _get_iterator();
+  WholeSpaceIterator _get_snapshot_iterator();
 };