DBM (컴퓨팅)

3. 구현체

오리지널 AT&T dbm 라이브러리는 여러 구현체로 대체되었다.^[11] 주요 구현체는 다음과 같다.

• ndbm ("new dbm"): 새로운 기능을 갖춘 원본 dbm 기반이다.
• GDBM ("GNU dbm"): GNU 라이브러리의 재작성 버전이다.^[12]
• sdbm ("small dbm"): dbm의 퍼블릭 도메인 재작성 버전이다.^[13][14]
• 버클리 DB
• QDBM ("Quick Database Manager"): Tokyo/Kyoto Cabinet과 동일한 기술을 많이 사용하는 고성능 dbm이다.
• TDB ("Trivial Database"): Samba에서 사용하는 간단한 데이터베이스이다.
• LMDB (LMDB): copy-on-write 메모리 맵 파일 B+ 트리 구현이다.

• cdb ("constant database")
• Tkrzw: Kyoto Cabinet 및 Tokyo Cabinet의 Apache 2.0 라이선스 후속 제품이다.
• WiredTiger: 전통적인 행 지향 및 열 지향 스토리지를 갖춘 데이터베이스이다.
• MDBM: 야후! inc.에서 오픈 소스화한 dbm 구현체이다.
• JDBM

3. 1. ndbm (new dbm)

3. 2. GDBM (GNU dbm)

3. 3. sdbm (small dbm)

3. 4. 버클리 DB

3. 5. QDBM (Quick Database Manager)

3. 6. TDB (Trivial Database)

3. 7. LMDB (Lightning Memory-Mapped Database)

3. 8. 기타 구현체

• cdb ("constant database", 상수 데이터베이스): Daniel J. Bernstein이 개발한 데이터베이스로, 데이터베이스 파일은 생성 및 읽기만 가능하며 수정할 수 없다.^[11]
• Tkrzw: Kyoto Cabinet 및 Tokyo Cabinet의 Apache 2.0 라이선스 후속 제품이다.^[11]
• WiredTiger: 전통적인 행 지향 및 열 지향 스토리지를 갖춘 데이터베이스이다.^[11]
• MDBM: 야후! inc.에서 오픈 소스화한 dbm 구현체이다.^[11]
• JDBM^[11]

4. 신뢰성

2018년 여러 DBM 계열 데이터베이스를 대상으로 한 AFL 퍼징 테스트에서 데이터베이스 파일이 손상되었거나 유효하지 않은 경우 구현에 많은 문제가 노출되었다. 다니엘 J. 번스타인의 ''freecdb''만이 충돌을 보이지 않았다. gdbm, tdb 및 lmdb 제작자는 신속하게 대응했다. 버클리 DB는 다른 문제의 엄청난 양으로 인해 뒤쳐졌다.^[8] 수정 사항은 구버전에 고정되어 라이선스 변경으로 인해 오픈 소스 소프트웨어 사용자에게는 관련이 없을 것이다.^[7]

참조

_[1] 웹사이트 Crash Tolerance https://www.gnu.org.[...] 2021-10-03
_[2] 웹사이트 Crashproofing the Original NoSQL Key-Value Store https://queue.acm.or[...] 2021-10-03
_[3] 웹사이트 sdbm.bun http://www.cse.yorku[...] 2019-05-08
_[4] 웹사이트 Ruby SDBM library https://github.com/r[...]
_[5] 웹사이트 QDBM: Quick Database Manager https://fallabs.com/[...] 2006
_[6] 웹사이트 tdb: Main Page https://tdb.samba.or[...]
_[7] 간행물 New project goal: Get rid of Berkeley DB (post jessie) https://lists.debian[...] Debian 2014-06-19
_[8] 웹사이트 oss-security - Fun with DBM-type databases... https://www.openwall[...] 2018-06-16
_[9] 서적 DBMs have been with us since the early days of computing, when the need for fast keyed lookups was recognized. The original DBM is a UNIX-based library and file format for fast, highly-scalable keyed access to data. It was followed (in order) by NDBM ('new DBM'), GDBM ('GNU DBM'), and the Berkeley DB. This last is by far the most advanced, and the only DBM under active development today. Nevertheless, all of the DBMs from NDBM onward provide the same core functionality used by most programs, including Apache. A minimal-implementation SDBM is also bundled with [[Apache Portable Runtime|APR]], and is available to applications along with the other DBMs.
Although NDBM is now old - like the city named New Town ('Neapolis') by the Greeks in about 600BC and still called Naples today - it remains the baseline DBM. NDBM was used by early Apache modules such as the Apache 1.x versions of mod_auth_dbm and mod_rewrite. Both GDBM and Berkeley DB provide NDBM emulations, and Linux distributions ship with one or other of these emulations in place of the 'real' NDBM, which is excluded for licensing reasons. Unfortunately, the various file formats are totally incompatible, and there are subtle differences in behaviour concerning database locking. These issues led a steady stream of Linux users to report problems with DBMs in Apache 1.x.
_[10] 서적 The most common [single-key] format is called DBM. Most modern versions of Unix have a DBM library installed as standard, though this is not true of some older systems. The two most common DBM libraries are ''ndbm'' (standard on Solaris and IRIX) and Berkeley DB Version 2 or 3 (standard on several free operating systems). Exim supports both of these, as well as the older Berkeley DB Version 1, ''gdbm'', and ''tdb''.
_[11] 서적 Most UNIX systems have some kind of DBM database. DBM is a set of library routines that manages data files consisting of key and value pairs. The DBM routines control how users enter and retrieve information from the database. Although it isn't the most powerful mechanism for storing information, using DBM is a faster method of retrieving information than using a flat file. Because most UNIX sites use one of the DBM libraries, the tools you need to store your information in a DBM database are readily available.
Almost as many flavors of the DBM libraries exist as there are UNIX systems. Although most of these libraries are compatible with each other, they all basically work the same way...
A list follows of some of the most popular DBM libraries available:{{bulleted list|'''DBM''' - DBM stores the database in two files. The first has the extension .Pag and contains the bitmap. The second, which has the extension .Dir, contains the data.|'''NDBM''' - NDBM is much like DBM but with a few additional features; it was written to provide better storage and retrieval methods. Also, NDBM enables you to open many databases, unlike DBM, in which you are allowed to have only one database open within your script. Like DBM, NDBM stores its information in two files using the extensions .Pag and .Dir.|'''SDBM''' - SDBM comes with the Perl archive, which has been ported to many platforms. Therefore, you can use DBM databases as long as a version of Perl exists for your computer. SDBM was written to match the functions provided with NDBM, so portability of code shouldn't be a problem. Perl is available on just about all popular platforms.|'''GDBM''' - GDBM is the GNU version of the DBM family of database routines. GDBM also enables you to cache data, reducing the time that it takes to write to the database. The database has no size limit; its size depends completely on your system's resources. GDBM database files have the extension .Db. Unlike DBM and NDBM, both of which use two files, GDBM only uses one file.|'''Berkeley db''' - The Berkeley db expands on the original DBM routines significantly. The Berkeley db uses hashed tables the same as the other DBM databases, but the library also can create databases based on a sorted balanced binary tree (BTREE) and store information with a record line number (RECNO). The method that you use depends completely on how you want to store and retrieve the information from a database. Berkeley db creates only one file, which has no extension."}}
_[12] 웹인용 GDBM https://www.gnu.org.[...]
_[13] 웹인용 sdbm.bun http://www.cse.yorku[...] 2019-05-08
_[14] 웹인용 class SDBM https://docs.ruby-la[...]
_[15] 웹인용 Tokyo Cabinet第1版基本仕様書 http://fallabs.com/t[...] 2010-08-05