Database with low memory requirements and Ruby interface

I need a database with low memory requirements for a small virtual server with few memory. At the moment I'm stuck with SQLite and Kyoto Cabinet or Tokyo Cabinet. The database should have a Ruby interface.

开发者_JAVA技巧Ideally I want to avoid key-value-stores, because I have “complex” queries (more complex than looking up a single key) and tuples as keys. On the other hand I don't want to have a fixed schema and avoid the planning and migration efforts of a SQL database. A database server is also not necessary because only a single application will use the database.

Do you have any recommendations and numbers for me?

1. There is schema-less Postgresql (Postgresql 9.2 + json). Not as hard/confusing to set up as I thought. You get lots of flexibility with queries while still getting the benefits of schema-less storage. PG 9.2 includes plv8js, a new language handler that allows you to create functions in JavaScript. Here is one example of how you can index and query JSON docs in PG 9.2: http://people.planetpostgresql.org/andrew/index.php?/archives/249-Using-PLV8-to-index-JSON.html

2. CouchDB (Use BigCouch. Based on CouchDB, but fewer bugs/problems.):

   • very low memory requirements.
   • schema-less.
   • HTTP-based interface. Ruby has plenty of HTTP clients. HTTP caching (like Varnish) can also speed reads.
   • creative/complex queries. You can create indexes and queries on any key in the document (record). You can get very creative with queries since the indexes are very programmable.

   Downsides:

   • Learning curve of setting up your queries/indexes.
   • You have to schedule a type of cleanup operation called "compaction".
   • Data will take up more space compared to other databases.
   • More: http://www.paperplanes.de/2010/7/26/10_annoying_things_about_couchdb.html

   If disk is cheap and memory expensive, it would make a good candidate for your needs.

   "...another strength of CouchDB, which has proven to serve thousands of concurrent requests only needed about 10MB of RAM - how awesome is that?!?!" (From: http://www.larsgeorge.com/2009/03/hbase-vs-couchdb-in-berlin.html )

SQLite3 is a great fit for what you are trying to do. It's used by a lot of companies as their embedded app database because it's flexible, fast, well tested, and has a small footprint. It's easy to create and blow away tables so it plays well with testing or single-application-use data stores.

The SQL language it uses is rich enough to do normal things but I'd recommend using Sequel with it. It's a great ORM and easily lets you treat it as a full-blown ORM, or drop all the way down to talking raw SQL to the DBM.

You are looking for a solution that only has a database file and no running server, probably. In that case, Sqlite should be a good choice - If you don't need it, just close the connection and that's it. Sqlite has everything that you need from and RDMS (expect for enforcing FK's directly, but that can be done with triggers), with a very little memory footprint, so in that case you are probably worried more about the memory your ORM (if any) uses.

Personally, I use sqlite for that use case as well, as it is portable and easy to access and install (which shouldn't be the problem on a server anyway, but in a desktop application it is).

BerkeleyDB with SQLite API is what you need. http://www.oracle.com/technetwork/database/berkeleydb/overview/sql-160887.html