Обсуждение: pgsql: Remove AtSubStart_Notify.

Remove AtSubStart_Notify.

Allocate notify-related state lazily instead. This makes trivial
subtransactions noticeably faster.

Patch by me, reviewed and tested by Dilip Kumar, Kyotaro Horiguchi,
and Jeevan Ladhe.

Discussion: https://postgr.es/m/CA+TgmobE1J22S1eC-6N-je9LgrcwZypkwp+zH6JXo9mc=4Nk3A@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/967e276e9f6b485c8577371713a323bf277b6902

Modified Files
--------------
src/backend/access/transam/xact.c |   1 -
src/backend/commands/async.c      | 297 +++++++++++++++++++++-----------------
src/include/commands/async.h      |   1 -
3 files changed, 164 insertions(+), 135 deletions(-)