gnus-summary: sorting after / s restriction takes unexpectedly long

[Daniel Ortmann]

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In GNU Emacs 21.1.1 (i386--freebsd, X toolkit, Xaw3d scroll bars)
 of 2001-11-09 on pyrl.eye
configured using `configure  --prefix=/usr/local i386--freebsd'
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: nil
  locale-coding-system: nil
  default-enable-multibyte-characters: t

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

The behavior being described has existed in emacs gnus for quite
awhile.  I am reporting it now since I realize it is probably something
that could use fixing.

Gnus Problem:

    Sorting a gnus-summary buffer of (say) 4000 entries takes an
    expectedly long amount of time.  After performing one of the
    gnus-summary-limit-* functions such as gnus-summary-limit-to-subject
    (invoked by [?/ ?s] in the summary buffer) to limit the lines about
    40-50, the sorting is _still_ long, unexpectedly long.

My Expectation:

    I expected that sorting on the restricted buffer would be much
    faster than on the entire buffer.

My Speculation:

    Perhaps sorting in a restricted summary buffer is still being
    performed on the _entire_ buffer contents rather than on the subset?
    I had imagined that each restriction/limit request would produce
    some type of sub-list with entries pointing back to the real summary
    lines; then sorting the sub-list should be fast automatically.

Steps To Repeat:

    1) Start emacs, gnus, and select any large newsgroup by pressing
       4000 <enter> in the article selection buffer.  (The size of the
       individual articles does not matter since we will only be working
       in the gnus-summary buffer.)

    2) Note the time it takes to sort by subject when you press
       C-c C-s C-s

    3) Pick a phrase that exists in 10-50 subjects and perform a filter
       action using gnus-summary-limit-to-subject by pressing / s,
       typing in the phrase and pressing <enter>.

    4) Now note the time it takes to re-sort the buffer, perhaps by
       subject as before, perhaps by date using C-c C-s C-d, or by # of
       lines with C-c C-s C-l.

The Result:

    The time it takes to sort the buffer is unexpectedly long.

Recent input:
M-x r e p o r t - e m a c s TAB RET

Recent messages:
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Loading /usr/local/libexec/emacs/21.1/i386--freebsd/fns-21.1.1.el 
(source)...done
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-- 
Daniel Ortmann, 2414 30 Av NW, #D, Rochester, MN 55901
ortmann@isl.net (h)   / 507.288.7732 (h)
dortmann@lsil.com (w) / 507.529.3887 (w)