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<p>
Next: <a href="Configuration-API.html#Configuration-API" accesskey="n" rel="next">Configuration API</a>, Previous: <a href="Search-Algorithm.html#Search-Algorithm" accesskey="p" rel="prev">Search Algorithm</a>, Up: <a href="Controlling-where-ASDF-searches-for-systems.html#Controlling-where-ASDF-searches-for-systems" accesskey="u" rel="up">Controlling where ASDF searches for systems</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="Caching-Results-1"></a>
<h3 class="section">8.9 Caching Results</h3>

<p>The implementation is allowed to either eagerly compute the information
from the configurations and file system, or to lazily re-compute it
every time, or to cache any part of it as it goes.
In practice, the recommended <code>source-registry</code> eagerly collects and caches results
and you need to explicitly flush the cache for change to be taken into account,
whereas the old-style <code>*central-registry*</code> mechanism queries the filesystem every time.
</p>
<p>To explicitly flush any information cached by the system
after a change was made in the filesystem, See <a href="Configuration-API.html#Configuration-API">Configuration API</a>,
and e.g. call <code>asdf:clear-source-registry</code>.
</p>
<p>Starting with ASDF 3.1.4, you can also explicitly build a persistent cache
of the <samp>.asd</samp> files found under a tree:
when recursing into a directory declared by <code>:tree</code> and its transitive subdirectories,
if a file <samp>.cl-source-registry.cache</samp> exists containing a form
that is a list starting with <code>:source-registry-cache</code> followed by a list of strings,
as in <code>(:source-registry-cache <em>&quot;foo/bar.asd&quot; &quot;path/to/more.asd&quot; ...</em>)</code>,
then the strings are assumed to be <code>unix-namestring</code>s designating
the available asd files under that tree, and the recursion otherwise stops.
The list can also be empty, allowing to stop a costly recursion in a huge directory tree.
</p>
<p>To update such a cache after you install, update or remove source repositories,
you can run a script distributed with ASDF:
<code>tools/cl-source-registry-cache.lisp <em>/path/to/directory</em></code>.
To wholly invalidate the cache, you can
delete the file <samp>.cl-source-registry.cache</samp> in that directory.
In either case, for an existing Lisp process to see this change,
it needs to clear its own cache with e.g. <code>(asdf:clear-source-registry)</code>.
</p>
<p>Developers may safely create a cache in their development tree,
and we recommend they do it at the top of their source tree if
it contains more than a small number of files and directories;
they only need update it when they create, remove or move <samp>.asd</samp> files.
Software distribution managers may also safely create such a cache,
but they must be careful to update it every time they install, update or remove
a software source repository or installation package.
Finally, advanced developers who juggle with a lot of code
in their <code>source-registry</code> may manually manage such a cache,
to allow for faster startup of Lisp programs.
</p>
<p>This persistence cache can help you reduce startup latency.
For instance, on one machine with hundreds of source repositories,
such a cache shaves half a second at the startup
of every <code>#!/usr/bin/cl</code> script using SBCL, more on other implementations;
this makes a notable difference as to
their subjective interactivity and usability.
The speedup will only happen if the implementation-provided ASDF is recent enough
(3.1.3.7 or later); it is not enough for a recent ASDF upgrade to be present,
since the upgrade will itself be found but
after the old version has scanned the directories without heeding such a cache.
To upgrade the implementation-provided ASDF,
see <a href="Replacing-your-implementation_0027s-ASDF.html#Replacing-your-implementation_0027s-ASDF">Replacing your implementation's ASDF</a>.
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<p>
Next: <a href="Configuration-API.html#Configuration-API" accesskey="n" rel="next">Configuration API</a>, Previous: <a href="Search-Algorithm.html#Search-Algorithm" accesskey="p" rel="prev">Search Algorithm</a>, Up: <a href="Controlling-where-ASDF-searches-for-systems.html#Controlling-where-ASDF-searches-for-systems" accesskey="u" rel="up">Controlling where ASDF searches for systems</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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cl-asdf 2:3.3.1-1 / usr / share / doc / cl-asdf / asdf / Caching-Results.html
