Simple db using append only log file. This runs in a single thread and is not suitable for any production environment. Implemented for learning purpose.
Implemented methods:
- get
<key> - set
<key><value> - delete
<key>
A log file will be used to append values while an in-memory hashmap will keep track of the pair:
- key
- IndexValue object which has the 2 following properties:
- offset: where to read the value in the file so we don't need to read the whole file
- bytes_to_read: how many bytes to read from offset
When log file exceeds a certain size (1 MB in the main.rs file usage of the db), compaction process will kick-in. Compaction will remove any duplicate values in the log file, we can have many of those when updating multiple times a key's associated value.
Technically this could be thread-safe if we put a mutex on the set method (which writes to the log file AND runs compaction when needed).
We could also produce multiple log files that each have its own hashmap, read-only ones and 1 active where writes still happen. Compaction would then work accross all logs files.