wellquite.org/golmdb

GoLMDB

This is a high-level binding to LMDB.

go get wellquite.org/golmdb@latest

This binding uses cgo and so to build, you'll need a working cgo environment: a supported C compiler suite, alongside the LMDB library and headers. LMDB is extremely widely used and is available on "all" platforms, so it shouldn't be difficult to get it on your platform. This binding has been predominately developed with version 0.9.29, which is the current version at the time of writing.

There are several Go bindings to LMDB available. All of them (that I can find) are fairly low-level and tend to mirror the C API into Go. This provides a lot of flexibility, but it leaves a lot of work to do too.

This binding is high-level. It does not attempt to support all the features of LMDB, nor expose the full low-level LMDB API. It provides:

• batching of updates: read-write transactions will be batched together automatically up to some limit set by a parameter. This allows you to control (to some extent) the trade-off between latency and throughput: smaller batches will result in more fsyncs going on, but may reduce latency; larger batches may increase latency, but there will be fewer fsyncs.
• automatic resizing: LMDB returns an error if its database file fills up. LMDB also has an API to increase the size of its database file. In general LMDB recommends starting with a huge file size for its database, and relying on the underlying filesystem supporting sparse files, which most modern file systems do. However, there's still always the risk that you end up putting in more data than you thought you would, so this binding automatically copes and increases the size when necessary.
• minimal copy of data from Go to C and back again. In most cases, Puts of a key-value pair can be written directly to disk without further copies being taken. Reads can access the data on disk with just a single copy (i.e. the copy managed by the OS as part of the mmap) provided care is taken to not use the data beyond the lifetime of the transaction.

Many of the more advanced flags from LMDB are still available, for example flags to turn off syncing. These flags can make updates/writes appear to be much faster. But they are also foot-guns: they can be used safely in certain circumstances, but they're highly likely to blow your foot off and destroy your data if you're not careful. This binding will not save you from yourself! Refer back to the original LMDB docs if you're in any doubt.

There are a few more words about this over on my blog