external/ibm-public/postfix/dist/proto/CDB_README.html

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  16 <h1><img src="postfix-logo.jpg" width="203" height="98" ALT="">Postfix CDB Howto</h1>
  17
  18 <hr>
  19
  20 <h2>Introduction</h2>
  21
  22 <p> CDB (Constant DataBase) is an indexed file format designed by
  23 Daniel Bernstein. CDB is optimized exclusively for read access
  24 and guarantees that each record will be read in at most two disk
  25 accesses. This is achieved by forgoing support for incremental
  26 updates: no single-record inserts or deletes are supported.  CDB
  27 databases can be modified only by rebuilding them completely from
  28 scratch, hence the "constant" qualifier in the name.  </p>
  29
  30 <p> Postfix CDB databases are specified as "cdb:<i>name</i>", where
  31 <i>name</i> specifies the CDB file name without the ".cdb" suffix
  32 (another suffix, ".tmp", is used temporarily while a CDB file is
  33 under construction).  CDB databases are maintained with the postmap(1)
  34 or postalias(1) command. The DATABASE_README document has general
  35 information about Postfix databases.  </p>
  36
  37 <p> CDB support is available with Postfix 2.2 and later releases.
  38 This document describes how to build Postfix with CDB support. </p>
  39
  40 <h2>Building Postfix with CDB support</h2>
  41
  42 <p> These instructions assume that you build Postfix from source
  43 code as described in the INSTALL document. Some modification may
  44 be required if you build Postfix from a vendor-specific source
  45 package.  </p>
  46
  47 <p> Postfix is compatible with two CDB implementations: </p>
  48
  49 <ul>
  50
  51 <li> <p> The original cdb library from Daniel Bernstein, available
  52 from http://cr.yp.to/cdb.html, and </p>
  53
  54 <li> <p> tinycdb (version 0.5 and later) from Michael Tokarev,
  55 available from http://www.corpit.ru/mjt/tinycdb.html. </p>
  56
  57 </ul>
  58
  59 <p>  Tinycdb is preferred, since it is a bit faster, has additional
  60 useful functionality and is much simpler to use. </p>
  61
  62 <p>To build Postfix after you have installed tinycdb, use something
  63 like: </p>
  64
  65 <blockquote>
  66 <pre>
  67 % make tidy
  68 % CDB=../../../tinycdb-0.5
  69 % make -f Makefile.init makefiles "CCARGS=-DHAS_CDB -I$CDB" \
  70     "AUXLIBS=$CDB/libcdb.a"
  71 % make
  72 </pre>
  73 </blockquote>
  74
  75 <p> Alternatively, for the D.J.B. version of CDB:<p>
  76
  77 <blockquote>
  78 <pre>
  79 % make tidy
  80 % CDB=../../../cdb-0.75
  81 % make -f Makefile.init makefiles "CCARGS=-DHAS_CDB -I$CDB" \
  82     "AUXLIBS=$CDB/cdb.a $CDB/alloc.a $CDB/buffer.a $CDB/unix.a $CDB/byte.a"
  83 % make
  84 </pre>
  85 </blockquote>
  86
  87 <p> After Postfix has been built with cdb support, you can use
  88 "cdb" tables wherever you can use read-only "hash", "btree" or
  89 "dbm" tables. However, the "<b>postmap -i</b>" (incremental record
  90 insertion) and "<b>postmap -d</b>" (incremental record deletion)
  91 command-line options are not available. For the same reason the
  92 "cdb" map type cannot be used to store the persistent address
  93 verification cache for the verify(8) service, or to store
  94 TLS session information for the tlsmgr(8) service. </p>