This enables a bunch of features, notably ON_ERROR_ROLLBACK. It also
makes COPY failure (either in the server or psql) as a whole behave more
sanely in psql.
Additionally, having more commands in the same command line as COPY
works better (though since psql splits lines at semicolons, this doesn't
matter much unless you're using -c).
Also tighten a couple of switches on PQresultStatus() to add
PGRES_COPY_BOTH support and stop assuming that unknown statuses received
are errors; have those print diagnostics where warranted.
Author: Noah Misch
but seem like a separate patch since most of the remaining work is on the
executor side.) I took the opportunity to push selection of the grouping
operators for set operations into the parser where it belongs. Otherwise this
is just a small exercise in making prepunion.c consider both alternatives.
As with the recent DISTINCT patch, this means we can UNION on datatypes that
can hash but not sort, and it means that UNION without ORDER BY is no longer
certain to produce sorted output.