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fts: update docs and defaults

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This commit is contained in:
Martin Weinelt
2026-04-19 21:48:55 +02:00
parent f9d1435378
commit 198246f2c2
2 changed files with 50 additions and 32 deletions
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docs/fts.rst
+24 -22
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@@ -4,7 +4,7 @@ Full text search
By default, when your IMAP client searches for an email containing some
text in its *body*, dovecot will read all your email sequentially. This
is very slow and IO intensive. To speed body searches up, it is possible to
*index* emails with a plugin to dovecot, ``fts_flatcurve``.
*index* emails with the ``fts_flatcurve`` dovecot plugin.
Enabling full text search
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -20,48 +20,50 @@ To enable indexing for full text search here is an example configuration.
enable = true;
# index new email as they arrive
autoIndex = true;
# only query index
fallback = false;
};
};
}
The ``fallback`` parameter tells dovecot to fail any body search query that cannot
use an index. This prevents dovecot to fall back to the IO-intensive brute
force search.
Disabling the :option:`mailserver.fullTextSearch.fallback` option tells dovecot
to fail any body search query that cannot use an index. This prevents Dovecot to
fall back to the IO-intensive brute force search.
If you set ``autoIndex`` to ``false``, indices will be created when the IMAP client
issues a search query, so latency will be high.
If you set :option:`mailserver.fullTextSearch.autoIndex` to ``false``, indices
will be created when the IMAP client issues a search query, so latency will
be high.
Resource requirements
~~~~~~~~~~~~~~~~~~~~~~~~
Indices created by the full text search feature can take more disk
space than the emails themselves. By default, they are kept in the
emails location. When enabling the full text search feature, it is
recommended to move indices in a different location, such as
(``/var/lib/dovecot/indices``) by using the option
``mailserver.indexDir``.
Indices created by the full text search feature can take more disk space than
the emails themselves. By default, they are kept within the maildir. When
enabling the full text search feature, it is recommended to move indices in a
different location, such as (``/var/lib/dovecot/indices``) by configuring
:option:`mailserver.indexDir`.
.. warning::
When the value of the ``indexDir`` option is changed, all dovecot
indices needs to be recreated: clients would need to resynchronize.
When the value of the :option:`mailserver.indexDir` option is changed, all
dovecot indices needs to be recreated: clients would need to resynchronize.
Indexation itself is rather resource intensive, in CPU, and for emails with
large headers, in memory as well. Initial indexation of existing emails can take
hours. If the indexer worker is killed or segfaults during indexation, it can
be that it tried to allocate more memory than allowed. You can increase the memory
limit by eg ``mailserver.fullTextSearch.memoryLimit = 2000`` (in MiB).
hours. If the indexer worker is killed or segfaults during indexation, it can be
that it tried to allocate more memory than allowed. You can increase the default
memory limit through :option:`mailserver.fullTextSearch.memoryLimit`.
Mitigating resources requirements
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
You can:
* exclude some headers from indexation with ``mailserver.fullTextSearch.headerExcludes``
* disable expensive token normalisation in ``mailserver.fullTextSearch.filters``
* disable automatic indexation for some folders with
``mailserver.fullTextSearch.autoIndexExclude``. Folders can be specified by
name (``"Trash"``), by special use (``"\\Junk"``) or with a wildcard.
* exclude some headers from indexation with :option:`mailserver.fullTextSearch.headerExcludes`
* disable expensive token normalisation in :option:`mailserver.fullTextSearch.filters`
* disable automatic indexation for individual mailboxes by overriding
`fts_autoindex`_ on the mailbox level. This is exposed via
:option:`mailserver.mailboxes`, where all default mailboxes are defined.
.. _fts_autoindex: https://doc.dovecot.org/main/core/plugins/fts.html#fts_autoindex