Fix Gnus registry pruning and sorting, and rename file

* lisp/gnus/gnus-registry.el (gnus-registry-prune-factor): Add new variable.
(gnus-registry-max-pruned-entries): Remove obsolete variable.
(gnus-registry-cache-file): Change default
filename extension to "eieio".
(gnus-registry-read): Add new function, split out from
`gnus-registry-load', that does the actual object reading.
(gnus-registry-load): Use it. Add condition case handler to check for
old filename extension and rename to the new one.
(gnus-registry-default-sort-function): New variable to specify a sort
function to use when pruning.
(gnus-registry-save, gnus-registry-insert): Use it.
(gnus-registry-sort-by-creation-time): Define a default sort function.

* lisp/gnus/registry.el (registry-db): Consolidate the :max-hard and
:max-soft slots into a :max-size slot.
(registry-db-version): Add new variable for database version number.
(registry-prune): Use :max-size slot. Accept and use a sort-function
argument.
(registry-collect-prune-candidates): Add new function for finding
non-precious pruning candidates.
(registry-prune-hard-candidates, registry-prune-soft-candidates):
Remove obsolete functions.
(initialize-instance): Upgrade registry version when starting.

* doc/misc/gnus.texi (Gnus Registry Setup): Explain pruning changes.
Mention gnus-registry-prune-factor. Explain sorting changes and
gnus-registry-default-sort-function. Correct file extension.

1 files changed, 22 insertions, 5 deletions

diff --git a/doc/misc/gnus.texi b/doc/misc/gnus.texi
index 57aee27e2b1..6e3dced25d4 100644
--- a/doc/misc/gnus.texi
+++ b/doc/misc/gnus.texi
@@ -25953,17 +25953,34 @@ the word ``archive'' is not followed.
 
 @defvar gnus-registry-max-entries
 The number (an integer or @code{nil} for unlimited) of entries the
-registry will keep.
+registry will keep.  If the registry has reached or exceeded this
+size, it will reject insertion of new entries.
 @end defvar
 
-@defvar gnus-registry-max-pruned-entries
-The maximum number (an integer or @code{nil} for unlimited) of entries
-the registry will keep after pruning.
+@defvar gnus-registry-prune-factor
+This option (a float between 0 and 1) controls how much the registry
+is cut back during pruning.  In order to prevent constant pruning, the
+registry will be pruned back to less than
+@code{gnus-registry-max-entries}.  This option controls exactly how
+much less: the target is calculated as the maximum number of entries
+minus the maximum number times this factor.  The default is 0.1:
+i.e. if your registry is limited to 50000 entries, pruning will try to
+cut back to 45000 entries.  Entries with keys marked as precious will
+not be pruned.
+@end defvar
+
+@defvar gnus-registry-default-sort-function
+This option specifies how registry entries are sorted during pruning.
+If a function is given, it should sort least valuable entries first,
+as pruning starts from the beginning of the list.  The default value
+is @code{gnus-registry-sort-by-creation-time}, which proposes the
+oldest entries for pruning.  Set to nil to perform no sorting, which
+will speed up the pruning process.
 @end defvar
 
 @defvar gnus-registry-cache-file
 The file where the registry will be stored between Gnus sessions.  By
-default the file name is @code{.gnus.registry.eioio} in the same
+default the file name is @code{.gnus.registry.eieio} in the same
 directory as your @code{.newsrc.eld}.
 @end defvar