XDG: Tidying Recoll data storage
The default storage structure of Recoll configuration and index data is quite at odds with what recommends the XDG Base Directory Specification, the reason being that it predates said spec.
By default, Recoll stores all its data in a single directory: '$HOME/.recoll'
This is not going to change, because it would be quite disturbing for current users.
However, the location of this directory can be modified using the $RECOLL_CONFDIR environment variable.
Furthermore all significant Recoll data categories can be moved away from the configuration directory (maybe to '$HOME/.cache'), by setting configuration variables:
dbdir defines the location for storing the Xapian index. This could be set to, e.g., '$HOME/.cache/recoll/xapiandb'. It is quite recommended that this directory be dedicated to Xapian (don’t store other things in there).
mboxcachedir defines the location for caching access speedup information about mail folders in mbox format. e.g. '$HOME/.cache/recoll/mboxcache'
New in 1.22: you can use aspellDictDir to define the storage location for the aspell spelling approximation dictionary. E.g. '$HOME/.cache/recoll'
webcachedir may be used to define where the visited web pages archive is stored. E.g. '$HOME/.cache/recoll/webcache'. This is only used if you activate the Firefox plugin and web history indexing. You may want to think a bit more about where to store it, because, contrary to the above, this is not discardable data: your Recoll Web history goes away if you delete it.
If you use multiple Recoll configurations, each will have to be customized.
Once these are put away, there are still a few modifyiable files in the configuration directory, for example the 'recoll.pid' and 'history' files, but these are small files. Moving 'recoll.pid' away would be a serious headache because it is used by scripts.