Re: gnus-search-imap and quoted queries

[Sergio Durigan Junior <sergiodj@sergiodj.net>]

On Saturday, April 23 2022, Eric Abrahamsen wrote:

> Sergio Durigan Junior <sergiodj@sergiodj.net> writes:
>
>> On Tuesday, April 19 2022, I wrote:
>>
>>> I have GNUS configured to use a local Dovecot IMAP server (a fairly
>>> common setup, I think) and I've been trying to get gnus-search-imap
>>> working.  I set gnus-search-use-parsed-queries to t, by the way.
>>>
>>> I noticed that when I specify a quoted query as the search input, the
>>> results don't reflect what I'd expect.
>>
>> FWIW, I finally had some time to look deeper into this and found that
>> the culprit was the Dovecot FTS plugin I was using (fts-xapian).
>> It doesn't follow the IMAP RFC strictly and therefore can't/won't do
>> substring searches.
>>
>> I'm now using another Xapian-based plugin called fts-flatcurve which
>> DTRT.
>>
>> Thanks for the help, it's been fun investigating this problem.
>
> Hey that's pretty interesting. Looks like I'm using lucene, which seems
> to work fine. I wonder if it merits a brief mention in the manual that
> different backends behave differently.

I certainly wouldn't mind seeing this possible idiosyncrasy mentioned in
the manual.  WDYT about the patch below?

-- 
Sergio
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From ff85d8b3df751342de6b0071b9c17688086fe744 Mon Sep 17 00:00:00 2001
From: Sergio Durigan Junior <sergiodj@sergiodj.net>
Date: Sun, 1 May 2022 01:11:42 -0400
Subject: [PATCH] Mention different behaviours in IMAP FTS plugins

* doc/misc/gnus.texi (Search Engines): Mention different behaviours in
IMAP FTS plugins.
---
 doc/misc/gnus.texi | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/doc/misc/gnus.texi b/doc/misc/gnus.texi
index e51ae7d424d..03330224e09 100644
--- a/doc/misc/gnus.texi
+++ b/doc/misc/gnus.texi
@@ -21727,6 +21727,13 @@ Search Engines
 to manage updates yourself, though this will likely change in the
 future.
 
+If you use the IMAP search engine you may want to configure your IMAP
+server to provide Full Text Search (FTS) functionality, which greatly
+improves the performance and results.  Beware though that some FTS
+backends may not implement text search as described by RFC 3501, which
+states that substring search should be performed.  This difference in
+behaviour can ultimately affect the search results.
+
 Lastly, all search engines accept a @code{raw-queries-p} option.  This
 indicates that engines of this type (or this particular engine) should
 always use raw queries, never parsed (@pxref{Search Queries}).
-- 
2.35.1