Pack rats are nest builders. They use plant material such as twigs, sticks, and other available debris. They are particularly fond of shiny objects. A peculiar characteristic is that if they find something they want, they will drop what they are currently carrying—for example, a piece of cactus—and "trade" it for the new item.
Pack Rat is a small LSM (Log Structured Merge) database
engine that supports
the RESP protocol. Pack Rat's often build nests which
are akin to building out a log
structured merge tree using SSTables. I recently started writing this database engine in Java but naturally I switched
to rust; another call back to Pack Rat's
which will drop something old to pick up something new and shiny. Pack Rat has a few components to it.
- WAL (Write Ahead Log) for commits
- SSTable for storing data on disk
- Memtable for storing data in memory
- Offset index file
- Indexes are as follows (key, offset inside SSTable file on disk)
SSTable's are an indexing strategy used within LSM datastore's. It's a pretty simple methodology. There are two parts to SSTables:
- An in memory data structure called a Memtable
- Files on disk called SSTables
Data is written to the Memtable. Once the Memtable hits a certain threshold the data is serialized and written to an SSTable file on disk. This process continues over and over again. This causese a build up of SSTables on disk.
