[dovecot/core] 4db79f: lib-index: Remove extension record sync handlers

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/dovecot/core
  Commit: 4db79f4f779250c62f92922f4752c437bb82e68e
      https://github.com/dovecot/core/commit/4db79f4f779250c62f92922f4752c437bb82e68e
  Author: Timo Sirainen <timo.sirainen at dovecot.fi>
  Date:   2018-04-29 (Sun, 29 Apr 2018)

  Changed paths:
    M src/lib-index/mail-index-private.h
    M src/lib-index/mail-index-sync-ext.c
    M src/lib-index/mail-index.c

  Log Message:
  -----------
  lib-index: Remove extension record sync handlers

This is no longer used by anything, and it makes the fix in the following
commit much easier.

This was originally added in 6a19e109ee8c5a6f688da83a86a7f6abeb71abdd to
allow dovecot.index.cache updating to hook into updating cache offsets to
link cache records together. This was reimplemented in a different way in
131b073bdc3650083b00616dc778dd3017c2bbb5


  Commit: d5e0547cd5c8f1589c99cbf07a898b2da016da6d
      https://github.com/dovecot/core/commit/d5e0547cd5c8f1589c99cbf07a898b2da016da6d
  Author: Timo Sirainen <timo.sirainen at dovecot.fi>
  Date:   2018-04-29 (Sun, 29 Apr 2018)

  Changed paths:
    M src/lib-index/mail-index-sync-update.c

  Log Message:
  -----------
  lib-index: mail_index_sync_map() - Don't try to-resync extension updates

This was done to call extension record sync handlers, but the previous
commit removes them. Fixes a problem where obsolete cache offsets were
used in some situations:

 - Some cache updates are from external transactions and some are from
non-external transactions. This is because cache offset updates are being
added by whatever the parent index transaction is.

 - When mail_index_sync_map() is mapping MAIL_INDEX_SYNC_HANDLER_FILE, it
has already synced the map. But it's calling mail_index_sync_record()
for non-external transactions to call expunge handlers and extension
update handlers. It's calling the regular mail_index_sync_record() to do
this work.

 - But mail_index_sync_record() is actually still updating the map. So now
mail_index_sync_record() is called for all non-external cache updates,
but not for external cache updates! And since these are somewhat
randomly either external or non-external, the end result is that the
cache offset may be obsolete.


Compare: https://github.com/dovecot/core/compare/d0f3dde0ba3d...d5e0547cd5c8