# Optimize notmuch's performance
+[[!toc levels=2]]
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## Xapian 1.2.x database format: chert vs. flint
Xapian 1.2 (in contrast to 1.0.x) uses a new database format called
Backup your notmuch tags:
$ cd
- $ notmuch dump notmuch-dump-b4chert
+ $ notmuch dump --output=notmuch-dump-b4chert
Move away your old database:
Restore your tags:
- $ notmuch restore notmuch-dump-b4chert
+ $ notmuch restore --input=notmuch-dump-b4chert
Check whether you are on chert now:
Backup your database:
$ cd
- $ notmuch dump notmuch-dump-b4compact
+ $ notmuch dump --output=notmuch-dump-b4compact
Compact it:
* [Sebastian Spaeth](http://notmuchmail.org/pipermail/notmuch/2011/004048.html)
* [Pieter Praet](http://notmuchmail.org/pipermail/notmuch/2011/004175.html)
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