Re: Support for N synchronous standby servers - take 2

On Tue, Mar 22, 2016 at 9:58 PM, Kyotaro HORIGUCHI
<horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> Thank you for the revised patch.

Thanks for reviewing the patch!

> This version looks to focus on n-priority method. Stuffs for the
> other methods like n-quorum has been removed. It is okay for me.

I don't think it's so difficult to extend this version so that
it supports also quorum commit.

> StringInfo for double-quoted names seems to me to be overkill,
> since it allocates 1024 byte block for every such name. A static
> buffer seems enough for the usage as I said.

So, what about changing the scanner code as follows?

<xd>{xdstop} {
yylval.str = pstrdup(xdbuf.data);
pfree(xdbuf.data);
BEGIN(INITIAL);
return NAME;

> The parser is called for not only for SIGHUP, but also for
> starting of every walsender. The latter is not necessary but it
> is the matter of trade-off between simplisity and
> effectiveness.

Could you elaborate why you think that's not necessary?

BTW, in previous patch, s_s_names is parsed by postmaster during the server
startup. A child process takes over the internal data struct for the parsed
s_s_names when it's forked by the postmaster. This is what the previous
patch was expecting. However, this doesn't work in EXEC_BACKEND environment.
In that environment, the data struct should be passed to a child process via
the special file (like write_nondefault_variables() does), or it should
be constructed during walsender startup (like latest version of the patch
does). IMO the latter is simpler.

Regards,

--
Fujii Masao