Re: Log size in bytes of query result

> On Wed, May 22, 2019 at 2:51 PM Franklin Haut <franklin(dot)haut(at)gmail(dot)com> wrote:
>
> By my analysis, I see that the most efficient way to perform this control
> would be in the existing medium in postgresql that is the log file (pg_log)
> adding a few more variables for each query executed.

> On Fri, May 10, 2019 at 6:42 PM Sergei Kornilov <sk(at)zsrv(dot)org> wrote:
>
> We have any hooks that can be used for such purposes? Sometimes I think how
> to implement counters "bytes sent to client"/"bytes recv from client" in
> pg_stat_statements but did not found good place. Where we can accumulate such
> counters and how they can be accessible from extension? Extend DestReceiver
> or add counter directly in src/backend/libpq/pqcomm.c ?

For the records, I guess on Linux you can gather such kind of information via
ebpf, even without hooks in Postgres (if you avoid too frequent context
switches between kernel/user space via e.g. relying on send/recv, it should be
also efficient). I have a POC in my postgres-bcc repo, it looks like this:

$ net_per_query.py bin/postgres -c $container_id
attaching...
listening...
detaching...

sent
[16397:4026532567] copy pgbench_accounts from stdin: 16b
[16397:4026532567] alter table pgbench_accounts add primary key (aid): 96b
[16428:4026532567] postgres: backend 16428: 2k

received
[16397:4026532567] copy pgbench_accounts from stdin: 16m