Re: [PATCH] Full support for index LP_DEAD hint bits on standby - Mailing list pgsql-hackers

Hello, everyone.

Oh, I just realized that it seems like I was too naive to allow
standby to set LP_DEAD bits this way.
There is a possible consistency problem in the case of low
minRecoveryPoint value (because hint bits do not move PageLSN
forward).

Something like this:

LSN=10  STANDBY INSERTS NEW ROW IN INDEX (index_lsn=10)
<-----------minRecoveryPoint will go here
LSN=20  STANDBY DELETES ROW FROM HEAP, INDEX UNTACHED (index_lsn=10)
               REPLICA SCANS INDEX AND SET hint bits (index_lsn=10)
               INDEX IS FLUSHED (minRecoveryPoint=index_lsn=10)
               CRASH

On crash recovery, a standby will be able to handle queries after
LSN=10. But the index page contains hints bits from the future
(LSN=20).
So, need to think here.

Thanks,
Michail.