"The database was created by a later version of Rhythmbox"

Updated Rhythmbox from Lucid to Maverick's version, to see if it would improve cold startup times.  It didn't, but it did break sync with my iTouch, besides rescanning all my collection.  So I downgraded back to Lucid, only to find Rhythmbox had upgraded its database to a new version:

Could not load the music database:
The database was created by a later version of Rhythmbox. This version of Rhythmbox cannot read the database.

(No se pudo cargar la base de datos de la música:
Una versión posterior de Rhythmbox creó la base de datos.  Esta versión de Rhythmbox no puede leer la base de datos. en Español.)

So I went to take a look at the database at ~/.gnome2/rhythm

box/rhythmbox.xml, except it was not there. locate was no help, since my home directory is encrypted, but strace did the trick, as usual.

Turns out Rhythmbox has had it's user data in ~/.local/share/rhythmbox for a while now.  ~/.local/share is defined by an actual specification, XDG, which is also used for all the pretty Documents, Music and such directories.  Anything that helps reduce the home polka dot syndrome is more than welcome, and the specification is handy to know.  Take a look at  ~/.local/share and $XDG_CONFIG_DIRS for a quick overview of who uses it (not many, sadly).

Back to Rhythmbox, I could have just deleted it's database at ~/.local/share/rhythmbox, but since I like living on the edge... I changed the version from 1.7 back to <rhythmdb version="1.6">, which got me back to where I had started (but somewhat wiser).

I also noticed that there were quite a bunch of type ignore entries on the "database," about a third of the total number of entries.  And of those, two thirds were comprised by the FreeDB directory tree.  Removed the FreeDB directory and its ignore entries (all 6 MiB of them), which seems to have improved startup time slightly.

Well, the least I can ask for after all that is some placebo effect!