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Comment by dustingetz | Hacker News Reader

by my understanding, datomic's persistence[1] layer is just a big huge persistent[2] data structure. there is tons of literature, books, papers, etc about persistent data structures in the functional programming community.

[1][2] 'persistent' means different things here.

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So, Datomic is a persistent data structure persisted to nonvolatile storage... I've wanted one of these for at least the last 2 years.

If only there was an open source implementation of this concept that I could run on my own hardware. Does anyone know of such a beast?

And, no, I don't want to roll my own versioned/timestamped row schema in an RDBMS - been there, suffered that.

Acid-State for haskell (http://acid-state.seize.it/) is based on a similar ideology and in the public domain. (Oh, but minus the time dimension I'm afraid.)

Acid-State is quite different, it persists representations of operations to disk (to make it durable) and keeps the data structure in memory.

I'm working on a project to bring persistent data-structures to disk ( https://github.com/DanielWaterworth/Siege ). It's currently undergoing a rethink, hence the lack of recent activity, but it's still in development.

At small (one machine) scale you could store simply store entity$attribute$time as the key for the value in any sorted key-value store e.g. levelDB.

(that is, concatenate the entity, attribute name and timestamp in a lexically sorting string)

At larger scale, hyperdex http://hyperdex.org/ might do the job but I don't know much about it

key-values stores like levelDB are persistent [1], but they are not persistent [2].

[1] http://en.wikipedia.org/wiki/Persistence_(computer_science)

[2] http://en.wikipedia.org/wiki/Persistent_data_structure

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