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by davidhollander 5440 days ago
BDB is a key\value store for unordered data more similar to Tokyo Cabinet hash databases. Tokyo Cabinet hash databases are a much faster option than BDB if you only need unordered data.

LevelDB is for if you need ordered data, and a more appropriate comparison would be against a B+\tree database.
1 comments
stephth 5440 days ago
LevelDB is for if you need ordered data

LevelDB is slower with random reads, but that doesn't mean you shouldn't use it for unordered data - it's still quite fast.

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davidhollander 5440 days ago
>LevelDB is slower with random reads, but that doesn't mean you shouldn't use it for unordered data - it's still quite fast.

In a positive analysis (should rather than shouldn't), assuming no default choice, it seems rational to use Tokyo Cabinet or CDB _hashmaps_ for unordered data, and LevelDB for ordered data, from a datastructure and performance standpoint. To assert more would probably need a specific use case for context.

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stephth 5440 days ago
In a positive analysis (should rather than shouldn't), assuming no default choice, it seems rational to use Tokyo Cabinet or CDB _hashmaps_ for unordered data, and LevelDB for ordered data, from a datastructure and performance standpoint.

It's as rational as doing optimizations. If the specific performance is extremely critical, yes, it definitely makes sense. But LevelDB does well with random reads [1]. With all its features and its permissive license, I think it's a strong contender as developer's go-to embedded key-value db, like SQLite for relational data.

Don't get me wrong, I do think your comparison is valuable, but I'm afraid it could be misleading; I specially found the wording LevelDB is for if you need ordered data misleading. Someone could read it and assume that LevelDB doesn't do well with unordered data.

[1] Compare today's benchmarks with these http://fallabs.com/tokyocabinet/benchmark.pdf, it looks like random reads in LevelDB are quite faster than BDB.

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davidhollander 5440 days ago
> and its permissive license

Other variables such as licensing are context dependent. In my context, I generally use embedded databases in shared library form to store arbitrary serialized Lua (much faster to reload than JSON, no need to compile protocol buffers) on my own servers, so in my development context LGPL vs BSD is irrelevant. But perhaps not for an iPhone developer. TokyoCabinet already has excellent bindings for nearly every language I've used, but thats irrelevant to a developer whose application is also C.

> Compare today's benchmarks with these http://fallabs.com/tokyocabinet/benchmark.pdf, it looks like random reads in LevelDB are quite faster than BDB.

I'd bet BDB is a snail, BUT the benchmark you just linked tests 0 databases in common with the one released by Google. What can be observed is that using a hashmap (TC) was over 7X faster than randomly accessing the fastest ordered data structure by the same author (TC-BT-RND) :)

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