Re: Gripes about walsender command processing

Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> On 2020-Sep-15, Alvaro Herrera wrote:
>> I overlooked this in 2f9661311b83. From this perspective, I agree it
>> looks wrong. We still have to send *some* completion tag (the 'C'
>> message), but maybe we can invent a separate entry point in dest.c for
>> that -- EndReplicationCommand() or some such -- that takes values from a
>> separate enum?

> It seems simpler than that actually; we don't need to build a lot of
> infrastructure.

This looks moderately reasonable to me. However, with the process
title reporting I want to add, we're going to end up with a switch
that looks like

case T_IdentifySystemCmd:
+ set_ps_display("IDENTIFY_SYSTEM");
IdentifySystem();
+ EndReplicationCommand("IDENTIFY_SYSTEM");
break;

case T_BaseBackupCmd:
+ set_ps_display("BASE_BACKUP");
PreventInTransactionBlock(true, "BASE_BACKUP");
SendBaseBackup((BaseBackupCmd *) cmd_node);
+ EndReplicationCommand("BASE_BACKUP");
break;

which is starting to look a bit repetitive and copy-pasteo-prone.
I don't see an easy way to improve on it though. The only obvious
alternative would be to put another switch before the main one that
just fills a "const char *cmdtag" variable, but that seems ugly.

regards, tom lane