Horton

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

Dilip Kumar <dilipbalaut@gmail.com>

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From: Dilip Kumar <dilipbalaut@gmail.com>
To: Kartyshov Ivan <i.kartyshov@postgrespro.ru>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2024-01-22T05:49:57Z
Lists: pgsql-hackers 
On Wed, Jan 17, 2024 at 1:46 PM Kartyshov Ivan
<i.kartyshov@postgrespro.ru> wrote:
>
> Add some fixes and rebase.
>
While quickly looking into the patch, I understood the idea of what we
are trying to achieve here and I feel that a useful feature.  But
while looking at both the patches I could not quickly differentiate
between these two approaches.  I believe, internally at the core both
are implementing similar wait logic but providing different syntaxes.
So if we want to keep both these approaches open for the sake of
discussion then better first to create a patch that implements the
core approach i.e. the waiting logic and the other common part and
then add top-up patches with 2 different approaches that would be easy
for review.  I also see in v4 that there is no documentation for the
syntax part so it makes it even harder to understand.

I think this thread is implementing a useful feature so my suggestion
is to add some documentation in v4 and also make it more readable
w.r.t. What are the clear differences between these two approaches,
maybe adding commit message will also help.

-- 
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com

Commits

  1. Ensure standby promotion point in 043_wal_replay_wait.pl

  2. Minor cleanup related to pg_wal_replay_wait() procedure

  3. Adjust pg_wal_replay_wait() procedure behavior on promoted standby

  4. pg_wal_replay_wait(): Fix typo in the doc

  5. Implement pg_wal_replay_wait() stored procedure

  6. Revert: Implement pg_wal_replay_wait() stored procedure

  7. Call WaitLSNCleanup() in AbortTransaction()

  8. Clarify what is protected by WaitLSNLock

  9. Use an LWLock instead of a spinlock in waitlsn.c

  10. Use the pairing heap instead of a flat array for LSN replay waiters

  11. Minor improvements for waitlsn.c

  12. Make the order of the header file includes consistent