Re: [HACKERS] make async slave to wait for lsn to be replayed

Rebased and ready for review.
I left only versions (due to irreparable problems)

1) Classic (wait_classic_v4.patch)
https://www.postgresql.org/message-id/3cc883048264c2e9af022033925ff8db%40postgrespro.ru
==========
advantages: multiple wait events, separate WAIT FOR statement
disadvantages: new words in grammar



WAIT FOR  [ANY | ALL] event [, ...]
BEGIN [ WORK | TRANSACTION ] [ transaction_mode [, ...] ]
      [ WAIT FOR [ANY | ALL] event [, ...]]
event:
LSN value
TIMEOUT number_of_milliseconds
timestamp



2) After style: Kyotaro and Freund (wait_after_within_v3.patch)
https://www.postgresql.org/message-id/d3ff2e363af60b345f82396992595a03%40postgrespro.ru
==========
advantages: no new words in grammar
disadvantages: a little harder to understand



AFTER lsn_event [ WITHIN delay_milliseconds ] [, ...]
BEGIN [ WORK | TRANSACTION ] [ transaction_mode [, ...] ]
      [ AFTER lsn_event [ WITHIN delay_milliseconds ]]
START [ WORK | TRANSACTION ] [ transaction_mode [, ...] ]
      [ AFTER lsn_event [ WITHIN delay_milliseconds ]]


-- 
Ivan Kartyshov
Postgres Professional: www.postgrespro.com