Re: search engine for virtual group?

[Eric Abrahamsen <eric@ericabrahamsen.net>]

Eric S Fraga <e.fraga@ucl.ac.uk> writes:

> Hello all,
>
> I have an nnvirtual group that combines a number of nnml groups.  I
> would like gnus search to work on that folder using notmuch but gnus
> does not seem to allow setting the search engine for a virtual group.
> Any suggestions?

Interesting question! First of all I don't think it will ever work with
nnvirtual, as there's no integration of search and the nnvirtual backend
at all. You'll have to use the nnselect backend, which can do everything
that nnvirtual can do. Steps would be:

- Recreating the basic virtual setup using nnselect instead. I'm not
  100% how this should look, but I know it's doable. We may have to rope
  Andy in for advice. There should probably be a special interactive
  command to make this use-case easier.
- Searching the group: I _think_ this should work transparently, with no
  additional configuration. nnselect knows which component groups make
  up a virtual group, knows how to get a list of the servers that own
  those groups, and should be able to route the same search query to
  each of those servers. In theory you should be able to have a virtual
  group made of some groups from an IMAP server and some from a nnml
  server that uses notmuch, and results will be returned transparently
  from the two different search engines. I've never actually tried this,
  though (making an nnselect group from an nnselect group), so it might
  take a little tweaking. Basically I was waiting for someone to ask :)

> PS - I was confused by this description of a variable:
>
> gnus-search-engine is a variable without a source file.
>
> This variable is obsolete since 25.1; use 'gnus-search-engine
> instead

Some of this very confusing stuff (the byte compiler would produce
similarly nonsensical complaints) has been fixed recently. Though not
completely; when I do `describe-variable' I get:

gnus-search-engine’s value is ‘gnus-search-engine’

Abstract base class for Gnus search engines.

  This variable is obsolete since 25.1;
  use \='gnus-search-engine instead

:(