eleveldb - Erlang bindings to LevelDB datastore

This project provides Erlang bindings to a LevelDB datastore heavily optimised for Riak workloads. See the Riak LevelDB wiki for a breakdown of the optimisations.

Future Development

No further work on optimising the underlying store is currently being undertaken, only minimal fixes necessary for platform compatibility.

At present, this backend is slated for deprecation in OpenRiak 3.4 and removal in a subsequent release. Should a maintainer commit to ongoing support that strategy will be revisited.

Alternatives

• For Riak-like workloads, especially with large objects, the pure-Erlang LevelEd store is recommended.
• Erlang bindings to RocksDB can be found as part of the BarrellDB project.

Iterating Records

High-level Iterator Interface

The interface that most clients of eleveldb should use when iterating over a set of records stored in leveldb is fold, since this fits nicely with the Erlang way of doing things.

For those who need more control over the process of iterating over records, you can use direct iterator actions. Use them with great care.

Direct Iterator Actions

seek/next/prev

• seek: Move iterator to a new position.

• next: Move forward one position and return the value; do nothing else.

• prev: Move backward one position and return the value; do nothing else.

prefetch/prefetch_stop

• prefetch: Perform a next action and then start a parallel call for the subsequent next while Erlang processes the current next. The subsequent prefetch may return immediately with the value already retrieved.

• prefetch_stop: Stop a sequence of prefetch calls. If there is a parallel prefetch pending, cancel it, since we are about to move the pointer.

Warning

Either use prefetch/prefetch_stop or next/prev. Do not intermix prefetch and next/prev. You must prefetch_stop after one or more prefetch operations before using any of the other operations (seek, next, prev).