Reviewing LevelDBPart I, What is this all about?

time to read 2 min | 285 words

LevelDB is…

a fast key-value storage library written at Google that provides an ordered mapping from string keys to string values.

That is the project’s own definition. Basically, it is a way for users to store data in an efficient manner. It isn’t a SQL database. It isn’t even a real database in any sense of the word. What it is is a building block for building databases. It handles writing and reading to disk, and it supports atomicity. But anything else is on you (from transaction management to more complex items).

As such, it appears perfect for the kind of things that we need to do. I decided that I wanted to get to know the codebase, especially since at this time, I can’t even get it to compile Sad smile. The fact that this is a C++ codebase, written by people who eat & breath C++ for a living is another reason why. I expect that this would be a good codebase, so I might as well sharpen my C++-foo at the same time that I grok what this is doing.

The first thing to do is to look at the interface that the database provides us with:


That is a very small surface area, and as you can imagine, this is something that I highly approve of. It make it much easier to understand and reason about. And there is some pretty complex behavior behind this, which I’ll be exploring soon.

More posts in "Reviewing LevelDB" series:

  1. (26 Apr 2013) Part XVIII–Summary
  2. (15 Apr 2013) Part XVII– Filters? What filters? Oh, those filters…
  3. (12 Apr 2013) Part XV–MemTables gets compacted too
  4. (11 Apr 2013) Part XVI–Recovery ain’t so tough?
  5. (10 Apr 2013) Part XIV– there is the mem table and then there is the immutable memtable
  6. (09 Apr 2013) Part XIII–Smile, and here is your snapshot
  7. (08 Apr 2013) Part XII–Reading an SST
  8. (05 Apr 2013) Part XI–Reading from Sort String Tables via the TableCache
  9. (04 Apr 2013) Part X–table building is all fun and games until…
  10. (03 Apr 2013) Part IX- Compaction is the new black
  11. (02 Apr 2013) Part VIII–What are the levels all about?
  12. (29 Mar 2013) Part VII–The version is where the levels are
  13. (28 Mar 2013) Part VI, the Log is base for Atomicity
  14. (27 Mar 2013) Part V, into the MemTables we go
  15. (26 Mar 2013) Part IV
  16. (22 Mar 2013) Part III, WriteBatch isn’t what you think it is
  17. (21 Mar 2013) Part II, Put some data on the disk, dude
  18. (20 Mar 2013) Part I, What is this all about?