Re: Simplify standby state machine a bit in WaitForWALToBecomeAvailable()

On Tue, Jan 03, 2023 at 02:53:10PM +0530, Bharath Rupireddy wrote:
> In summary:
> the flow when the standby is in crash recovery is pg_wal -> [archive
> -> pg_wal -> stream] -> [archive -> pg_wal -> stream] -> [] -> [] ...
> the flow when the standby is in archive recovery is [archive -> pg_wal
> -> stream] -> [archive -> pg_wal -> stream] -> [] -> [] ...

This is my understanding as well.

> The proposed patch makes the inherent state change to pg_wal after
> failure to read from archive in XLogFileReadAnyTLI() to explicit by
> setting currentSource to XLOG_FROM_PG_WAL in the state machine. I
> think it doesn't alter the existing state machine or add any new extra
> lookups in pg_wal.

I'm assuming this change would simplify your other patch that modifieѕ
WaitForWALToBecomeAvailable() [0]. Is that correct?

[0] https://commitfest.postgresql.org/41/3663/

--
Nathan Bossart
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