# mdb

An in-process, in-memory database for Go.

## TO DO

* [ ] kvstore: tests

## Structure

### Files

```
wal/<id>/data
wal/<id>/length
wal/<id>/archived
max-committed-id
write-lock
commit-lock
```

`<day-ts>` is the unix timestamp / 86400. Therefore a new segment will be
created every day. The data file is append-only, and the length is written
atomically.

`write-lock` is used by `flock` to ensure there's only one
writer. `commit-lock` is used by the commit routine. This routine will commit
data to the database and update `max-committed-id` atomically.

### Code

```
retry/
wal/
  segment/
storage/
```

## WAL File Format

The WAL file consists of an 8 byte minimum ID followed by a stream of entries
of the form

```
(4)           Data length
(Data length) Data
(8)           ID.
```

This allows us to quickly get the min and max IDs from the file, and iterate
though the segment from the beginning.