QDBM: Quick Database Manager

Copyright (C) 2000-2006 Mikio Hirabayashi
Last Update: Thu, 26 Oct 2006 15:00:20 +0900


QDBM is a library of routines for managing a database. The database is a simple data file containing records, each is a pair of a key and a value. Every key and value is serial bytes with variable length. Both binary data and character string can be used as a key and a value. There is neither concept of data tables nor data types. Records are organized in hash table or B+ tree.

As for database of hash table, each key must be unique within a database, so it is impossible to store two or more records with a key overlaps. The following access methods are provided to the database: storing a record with a key and a value, deleting a record by a key, retrieving a record by a key. Moreover, traversal access to every key are provided, although the order is arbitrary. These access methods are similar to ones of DBM (or its followers: NDBM and GDBM) library defined in the UNIX standard. QDBM is an alternative for DBM because of its higher performance.

As for database of B+ tree, records whose keys are duplicated can be stored. Access methods of storing, deleting, and retrieving are provided as with the database of hash table. Records are stored in order by a comparing function assigned by a user. It is possible to access each record with the cursor in ascending or descending order. According to this mechanism, forward matching search for strings and range search for integers are realized. Moreover, transaction is available in database of B+ tree.

QDBM is written in C, and provided as APIs of C, C++, Java, Perl, and Ruby. QDBM is available on platforms which have API conforming to POSIX. QDBM is a free software licensed under the GNU Lesser General Public License.


The following are documents of QDBM. They are contained also in the source package.


The following are packages of QDBM. The Linux binary package contains APIs for C, C++, and Java. It contains CGI scripts also. The Windows binary package contains APIs for C and Java. It contains CGI scripts also.


The following are links to applications of QDBM. If you run or find a project using QDBM, please tell it, and it will added to this list.


There are many followers of UNIX DBM. Select the best suited one for your products. NDBM is ancient and you should not use it. SDBM is maintained by Apache Project, and GDBM is maintained by GNU Project. They are most popular and time-tested. TDB is maintained by Samba Team. It allows multiple simultaneous writers. While CDB does not support updating at a runtime, it is the fastest. Berkeley DB is very multifunctional and ACID compliant. It is used in many commercial products. Finally, QDBM is balanced of performance, functionality, portability, and usability.


QDBM was written by Mikio Hirabayashi. You can contact the author by e-mail to `[email protected]'. However, as for topics which can be shared among other users, pleae send it to the mailing list. To join the mailing list, refer to `http://lists.sourceforge.net/lists/listinfo/qdbm-users'.

The project page on SourceForge.net is `http://sourceforge.net/projects/qdbm/'.

Update of this project is announced on Freshmeat.net at `http://freshmeat.net/projects/qdbm/'.