I enabled this plugin, but I keep getting the following error message
every time I refresh or rebuild the wiki:

    updating hyperestraier search index
    estcmd: ERROR: /home/wiki/wiki/.ikiwiki/hyperestraier: database problem
    estcmd gather -cm -bc -cl -sd -cl /home/wiki/wiki/.ikiwiki/hyperestraier - exited nonzero: 256
    done

Nevertheless, searching for pages works as expected, as far as I can tell.

--[[tschwinge]]

Have you upgraded hyperestradier since setting up the wiki? Apparently it
breaks a lot when it's upgraded, I find I often have to re-run ikiwiki
-setup after upgrading hyperestradier to force it to rebuilt its database,
then incremental updates work again for a while. This is one of the reasons
I want to change to a different search backend. --[[Joey]]

It was a completely fresh, completely untouched, unconfigured installation
of hyperestrainer (Debian testing on hurd-i386).
Even when running an `ikiwiki --setup [...] --rebuild` I get this:

    [...]
    rendering templates/note.mdwn
    rendering templates/popup.mdwn
    updating hyperestraier search index
    estcmd: ERROR: /home/wiki/wiki/.ikiwiki/hyperestraier: database problem
    estcmd gather -cm -bc -cl -sd -cl /home/wiki/wiki/.ikiwiki/hyperestraier - exited nonzero: 256
    done

Now I did a `rm -rf ~wiki/wiki/.ikiwiki/hyperestraier` and re-ran
`ikiwiki --setup [...] --rebuild`:

    [...]
    rendering templates/note.mdwn
    rendering templates/popup.mdwn
    updating hyperestraier search index
    estcmd: ERROR: /home/wiki/wiki/.ikiwiki/hyperestraier: database problem
    $ echo $?
    141

--[[tschwinge]]