pgsql: Remove the new UPSERT command tag and use INSERT instead.

Remove the new UPSERT command tag and use INSERT instead.

Previously, INSERT with ON CONFLICT DO UPDATE specified used a new
command tag -- UPSERT.  It was introduced out of concern that INSERT as
a command tag would be a misrepresentation for ON CONFLICT DO UPDATE, as
some affected rows may actually have been updated.

Alvaro Herrera noticed that the implementation of that new command tag
was incomplete; in subsequent discussion we concluded that having it
doesn't provide benefits that are in line with the compatibility breaks
it requires.

Catversion bump due to the removal of PlannedStmt->isUpsert.

Author: Peter Geoghegan
Discussion: 20150520215816.GI5885@postgresql.org

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/631d7490074cdaef8026db57a5f2772b8730f600

Modified Files
--------------
doc/src/sgml/protocol.sgml           |   13 +++----------
doc/src/sgml/ref/insert.sgml         |   21 +++++++--------------
src/backend/nodes/copyfuncs.c        |    1 -
src/backend/nodes/outfuncs.c         |    1 -
src/backend/optimizer/plan/planner.c |    2 --
src/backend/tcop/pquery.c            |   17 +++--------------
src/bin/psql/common.c                |    5 +----
src/include/catalog/catversion.h     |    2 +-
src/include/nodes/plannodes.h        |    2 --
9 files changed, 15 insertions(+), 49 deletions(-)