Re: BUG #15116: pg_recvlogical always fails

On Sat, Mar 17, 2018 at 09:20:26AM +0900, Michael Paquier wrote:
> At least slot creation fails.  One just needs to start up an instance
> and run that for example:
> $ pg_recvlogical --create-slot -S popo -d "dbname=postgres"
> pg_recvlogical: could not clear search_path: ERROR:  syntax erro

The issue is that support for plain SQL queries has been added in
PostgreSQL 10 for logical replication connections, however e170b8c8 has
missed the fact that this is not supported for older versions.  Hence,
two things need to happen as pg_recvlogical needs to be kept compatible
with past server versions:
1) Make the check deciding if search_path should be enforced smarter by
checking if the server version is newer than 10.  This needs to be
patched on HEAD and REL_10_STABLE.  recvlogical-search-path-fix.patch
does so.

2) Simply remove the check on past branches, as I recall that we
maintain downstream compatibility, but do not for example guarantee that
a Postgres 10 server would work with a 9.6's pg_recvlogical. This is
what recvlogical-search-path-fix-96.patch attached does.