Re: max_wal_senders must die

Greg Smith <greg(at)2ndquadrant(dot)com> writes:
> Josh Berkus wrote:
>> Well, now that you mention it, I also think that "hot standby" should be
>> the default. Yes, I know about the overhead, but I also think that the
>> number of our users who want easy replication *far* outnumber the users
>> who care about an extra 10% WAL overhead.

> ... But much like
> default_statistics_target, there needs to be some more formal work done
> on quantifying just how bad each of these overheads really are first.

Quite. Josh, have you got any evidence showing that the penalty is
only 10%? There are cases, such as COPY and ALTER TABLE, where
you'd be looking at 2X or worse penalties, because of the existing
optimizations that avoid writing WAL at all for operations where a
single final fsync can serve the purpose. I'm not sure what the
penalty for "typical" workloads is, partly because I'm not sure what
should be considered a "typical" workload for this purpose.

regards, tom lane