Re: Logical Replication and Character encoding

At Fri, 3 Mar 2017 21:31:24 -0500, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote in <88397afa-a8ec-8d8a-1c94-94a4795a3870(at)2ndquadrant(dot)com>
> On 3/3/17 14:51, Petr Jelinek wrote:
> > On 03/03/17 20:37, Peter Eisentraut wrote:
> >> On 2/27/17 00:23, Kyotaro HORIGUCHI wrote:
> >>> Yeah, the patch sends converted string with the length of the
> >>> orignal length. Usually encoding conversion changes the length of
> >>> a string. I doubt that the reverse case was working correctly.
> >>
> >> I think we shouldn't send the length value at all. This might have been
> >> a leftover from an earlier version of the patch.
> >>
> >> See attached patch that removes the length value.
> >>
> >
> > Well the length is necessary to be able to add binary format support in
> > future so it's definitely not an omission.
>
> Right. So it appears the right function to use here is
> pq_sendcountedtext(). However, this sends the strings without null
> termination, so we'd have to do extra processing on the receiving end.
> Or we could add an option to pq_sendcountedtext() to make it do what we
> want. I'd rather stick to standard pqformat.c functions for handling
> the protocol.

It seems reasonable. I changed the prototype of
pg_sendcountedtext as the following,

| extern void pq_sendcountedtext(StringInfo buf, const char *str, int slen,
| bool countincludesself, bool binary);

I think 'binary' seems fine for the parameter here. The patch
size increased a bit.

By the way, I noticed that postmaster launches logical
replication launcher even if wal_level < logical. Is it right?

regards,

--
Kyotaro Horiguchi
NTT Open Source Software Center