Single-file, persistent, sorted key-value store for Java (alternative to Berkeley DB) [closed]

Answer 1

--- Edited after seeing the size of the file ---

50 to 60 GiB files! It seems that you would have to know that your DB engine didn't load all of that in memory at once, and was very efficient in handling / scavenging off-loaded data backing blocks.

I don't know if Cloudscape is up to the task, and I wouldn't be surprised if it wasn't.

--- original post follows ---

Cloudscape often fits the bill. It's a bit more than Berkeley DB, but it gained enough traction to be distributed even with some JDK offerings.

Answer 2

I think SQLite is exactly what you want: Free (Public Domain), Single File Database, Zero-Configuration, Small Footprint, Fast, cross-platform, etc.. Here is a list of wrappers, there is a section for Java. Take a look to sqlite4java and read more on Java + SQLite here.

Answer 3

Consider ehcache. I show here a class for wrapping it as a java.util.Map. You can easily store Lists or other data structures as your values, avoiding the O(m*n) issue you are concerned with. ehcache is Apache 2.0 license, with an commercial enterprise version available by Terracotta. The open source version will allow you to spill your cache to disk, and if you choose not to evict cache entries it is effectively a persistent key-value store.

Answer 4

JavaDB aka Derby aka Cloudscape would be a decent choice; it's a pure Java SQL database, and it's included in the JRE, so you don't have to ship it with your code or require users to install it separately.

(It's actually not included in the JRE provided by some Linux package managers, but there it will be a separate package that is trivial to install)

However, Derby has fairly poor performance. An alternative would be H2 - again, a pure Java SQL database that stores a database in a single file, with a ~1MB jar under a redistributable license, but one that is considerably faster and lighter than Derby.

I've happily used H2 for a number of small projects. JBoss liked it enough that they bundled it in AS7. It's trivial to set up, and definitely worth a try.