Which embedded database capable of 100 million records has an efficient C or C++ API

I'm looking for a cross-platform database engine that can handle databases up hundreds of millions of records without severe degradation in query performance. It needs to have a C or C++ API which will allow easy, fast construction of records and parsing returned data.

Highly discouraged are products where data has to be translated to and from strings just to get it into the database. The technical users storing things like IP addresses don't want or need this overhead. This is a very important criteria so if you're going to refer to products, please be explicit about how they offer such a direct API. Not wishing to be rude, but I can use Google - please assume I've found most mainstream products and I'm asking because it's often hard to work out just what direct API they offer, rather than just a C wrapper around SQL.

It does not need to be an RDBMS - a simple ISAM record-oriented approach would be sufficient.

Whilst the primary need is for a single-user database, expansion to some kind of shared file or server operations is likely for future use.

Access to source code, either open source or via licensing, is highly desirable if the database comes from a small company. It must not be GPL or LGPL.


you might consider C-Tree by FairCom - tell 'em I sent you ;-)

i'm the author of hamsterdb.

tokyo cabinet and berkeleydb should work fine. hamsterdb definitely will work. It's a plain C API, open source, platform independent, very fast and tested with databases up to several hundreds of GB and hundreds of million items.

If you are willing to evaluate and need support then drop me a mail (contact form on hamsterdb.com) - i will help as good as i can!

bye Christoph

You didn't mention what platform you are on, but if Windows only is OK, take a look at the Extensible Storage Engine (previously known as Jet Blue), the embedded ISAM table engine included in Windows 2000 and later. It's used for Active Directory, Exchange, and other internal components, optimized for a small number of large tables.

It has a C interface and supports binary data types natively. It supports indexes, transactions and uses a log to ensure atomicity and durability. There is no query language; you have to work with the tables and indexes directly yourself.

ESE doesn't like to open files over a network, and doesn't support sharing a database through file sharing. You're going to be hard pressed to find any database engine that supports sharing through file sharing. The Access Jet database engine (AKA Jet Red, totally separate code base) is the only one I know of, and it's notorious for corrupting files over the network, especially if they're large (>100 MB).

Whatever engine you use, you'll most likely have to implement the shared usage functions yourself in your own network server process or use a discrete database engine.

I believe what you are looking for is BerkeleyDB: http://www.oracle.com/technology/products/berkeley-db/db/index.html

Never mind that it's Oracle, the license is free, and it's open-source -- the only catch is that if you redistribute your software that uses BerkeleyDB, you must make your source available as well -- or buy a license.

It does not provide SQL support, but rather direct lookups (via b-tree or hash-table structure, whichever makes more sense for your needs). It's extremely reliable, fast, ACID, has built-in replication support, and so on.

Here is a small quote from the page I refer to above, that lists a few features:

Data Storage

Berkeley DB stores data quickly and easily without the overhead found in other databases. Berkeley DB is a C library that runs in the same process as your application, avoiding the interprocess communication delays of using a remote database server. Shared caches keep the most active data in memory, avoiding costly disk access.

  • Local, in-process data storage
  • Schema-neutral, application native data format
  • Indexed and sequential retrieval (Btree, Queue, Recno, Hash)
  • Multiple processes per application and multiple threads per process
  • Fine grained and configurable locking for highly concurrent systems
  • Multi-version concurrency control (MVCC)
  • Support for secondary indexes
  • In-memory, on disk or both
  • Online Btree compaction
  • Online Btree disk space reclamation
  • Online abandoned lock removal
  • On disk data encryption (AES)
  • Records up to 4GB and tables up to 256TB

Update: Just ran across this project and thought of the question you posted: http://tokyocabinet.sourceforge.net/index.html . It is under LGPL, so not compatible with your restrictions, but an interesting project to check out, nonetheless.

For anyone finding this page a few years later, I'm now using LevelDB with some scaffolding on top to add the multiple indexing necessary. In particular, it's a nice fit for embedded databases on iOS. I ended up writing a book about it! (Getting Started with LevelDB, from Packt in late 2013).

One option could be Firebird. It offers both a server based product, as well as an embedded product.

It is also open source and there are a large number of providers for all types of languages.

SQLite would meet those criteria, except for the eventual shared file scenario in the future (and actually it could probably do that to if the network file system implements file locks correctly).

Many good solutions (such as SQLite) have been mentioned. Let me add two, since you don't require SQL:

  • HamsterDB fast, simple to use, can store arbitrary binary data. No provision for shared databases.
  • Glib HashTable module seems quite interesting too and is very common so you won't risk going into a dead end. On the other end, I'm not sure there is and easy way to store the database on the disk, it's mostly for in-memory stuff

I've tested both on multi-million records projects.

SQLite tends to be the first option. It doesn't store data as strings but I think you have to build a SQL command to do the insertion and that command will have some string building.

BerkeleyDB is a well engineered product if you don't need a relationDB. I have no idea what Oracle charges for it and if you would need a license for your application.

Personally I would consider why you have some of your requirements . Have you done testing to verify the requirement that you need to do direct insertion into the database? Seems like you could take a couple of hours to write up a wrapper that converts from whatever API you want to SQL and then see if SQLite, MySql,... meet your speed requirements.

As you are familiar with Fairtree, then you are probably also familiar with Raima RDM.

It went open source a few years ago, then dbstar claimed that they had somehow acquired the copyright. This seems debatable though. From reading the original Raima license, this does not seem possible. Of course it is possible to stay with the original code release. It is rather rare, but I have a copy archived away.

There used to be a product called b-trieve but I'm not sure if source code was included. I think it has been discontinued. The only database engine I know of with an ISAM orientation is c-tree.

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