CDB_README.html   [plain text]

<!doctype html public "-//W3C//DTD HTML 4.01 Transitional//EN"



<title>Postfix CDB Howto</title>

<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">



<h1><img src="postfix-logo.jpg" width="203" height="98" ALT="">Postfix CDB Howto</h1>



<p> CDB (Constant DataBase) is an indexed file format designed by
Daniel Bernstein. CDB is optimized exclusively for read access
and guarantees that each record will be read in at most two disk
accesses. This is achieved by forgoing support for incremental
updates: no single-record inserts or deletes are supported.  CDB
databases can be modified only by rebuilding them completely from
scratch, hence the "constant" qualifier in the name.  </p>

<p> Postfix CDB databases are specified as "<a href="CDB_README.html">cdb</a>:<i>name</i>", where
<i>name</i> specifies the CDB file name without the ".cdb" suffix
(another suffix, ".tmp", is used temporarily while a CDB file is
under construction).  CDB databases are maintained with the <a href="postmap.1.html">postmap(1)</a>
or <a href="postalias.1.html">postalias(1)</a> command. The <a href="DATABASE_README.html">DATABASE_README</a> document has general
information about Postfix databases.  </p>

<p> CDB support is available with Postfix 2.2 and later releases.
This document describes how to build Postfix with CDB support. </p>

<h2>Building Postfix with CDB support</h2>

<p> These instructions assume that you build Postfix from source
code as described in the <a href="INSTALL.html">INSTALL</a> document. Some modification may
be required if you build Postfix from a vendor-specific source
package.  </p>

<p> Postfix is compatible with two CDB implementations: </p>


<li> <p> The original cdb library from Daniel Bernstein, available
from <a href=""></a>, and </p>

<li> <p> tinycdb (version 0.5 and later) from Michael Tokarev,
available from <a href=""></a>. </p>


<p>  Tinycdb is preferred, since it is a bit faster, has additional
useful functionality and is much simpler to use. </p>

<p>To build Postfix after you have installed tinycdb, use something
like: </p>

% make tidy
% CDB=../../../tinycdb-0.5
% make -f Makefile.init makefiles "CCARGS=-DHAS_CDB -I$CDB" \
% make

<p> Alternatively, for the D.J.B. version of CDB:<p>

% make tidy
% CDB=../../../cdb-0.75
% make -f Makefile.init makefiles "CCARGS=-DHAS_CDB -I$CDB" \
    "AUXLIBS=$CDB/cdb.a $CDB/alloc.a $CDB/buffer.a $CDB/unix.a $CDB/byte.a"
% make

<p> After Postfix has been built with cdb support, you can use
"cdb" tables wherever you can use read-only "hash", "btree" or
"dbm" tables. However, the "<b>postmap -i</b>" (incremental record
insertion) and "<b>postmap -d</b>" (incremental record deletion)
command-line options are not available. For the same reason the
"cdb" map type cannot be used to store the persistent address
verification cache for the <a href="verify.8.html">verify(8)</a> service, or to store
TLS session information for the <a href="tlsmgr.8.html">tlsmgr(8)</a> service. </p>