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Re:LemonGraph – A log-based transactional graph by codebeaker on Sunday June 17, 2018 @06:28AM (#17331748)
What's a use-case for this? Is it like Neo4j or some other niche usecase (e.g mass surveillance graph, given the source)
Re:LemonGraph – A log-based transactional graph by antonvs on Sunday June 17, 2018 @11:40PM (#17335876)
Yes, it's like Neo4j but based on the in-memory database LMDB, presumably to provide high performance running on a single machine.

The link mentions that its use case is streaming seed set expansion, which allows you to identify communities based on a set of seeds. I wrote more about that in this comment: https://news.ycombinator.com/item?id=17335873

Re:LemonGraph – A log-based transactional graph by hyc_symas on Monday June 18, 2018 @07:01AM (#17337224)
Quibble: LMDB is a memory-mapped file database. It is not an in-memory database, although it generally outperforms all other in-memory databases.
Re:LemonGraph – A log-based transactional graph by antonvs on Friday June 22, 2018 @12:38PM (#17375357)
Thanks, this is the first I had heard of LMDB.

I actually love the idea of a memory-mapped database, I've often thought memory mapping isn't taken advantage of enough.

Re:LemonGraph – A log-based transactional graph by jsumrall on Sunday June 17, 2018 @11:29AM (#17332762)
It’s a graph database built on LMDB, so probably has the same use cases as you’d want to use LMDB in, but with some graph-y helpers.