| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
| Cc: | "Drouvot, Bertrand" <bertranddrouvot(dot)pg(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Robert Haas <robertmhaas(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Ibrar Ahmed <ibrar(dot)ahmad(at)gmail(dot)com>, Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com>, fabriziomello(at)gmail(dot)com, tushar <tushar(dot)ahuja(at)enterprisedb(dot)com>, Rahila Syed <rahila(dot)syed(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Minimal logical decoding on standbys |
| Date: | 2023-04-02 22:56:38 |
| Message-ID: | 6437cee668bb3e1157fe4a69ea0fa3377c1abaab.camel@j-davis.com |
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| Lists: | pgsql-hackers |
On Fri, 2023-03-31 at 02:50 -0700, Jeff Davis wrote:
> But if the ConditionVariableEventSleep() API is added, then I think
> we
> should change the non-recovery case to use a CV as well for
> consistency, and it would avoid the need for WalSndWakeup().
It seems like what we ultimately want is for WalSndWakeup() to
selectively wake up physical and/or logical walsenders depending on the
caller. For instance:
WalSndWakeup(bool physical, bool logical)
The callers:
* On promotion, StartupXLog would call:
- WalSndWakeup(true, true)
* XLogFlush/XLogBackgroundFlush/XLogWalRcvFlush would call:
- WalSndWakeup(true, !RecoveryInProgress())
* ApplyWalRecord would call:
- WalSndWakeup(switchedTLI, switchedTLI || RecoveryInProgress())
There seem to be two approaches to making that work:
1. Use two ConditionVariables, and WalSndWakeup would broadcast to one
or both depending on its arguments.
2. Have a "replicaiton_kind" variable in WalSnd (either set based on
MyDatabaseId==InvalidOid, or set at START_REPLICATION time) to indicate
whether it's a physical or logical walsender. WalSndWakeup would wake
up the right walsenders based on its arguments.
#2 seems simpler at least for now. Would that work?
Regards,
Jeff Davis
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