pgsql: Transaction chaining

Transaction chaining

Add command variants COMMIT AND CHAIN and ROLLBACK AND CHAIN, which
start new transactions with the same transaction characteristics as the
just finished one, per SQL standard.

Support for transaction chaining in PL/pgSQL is also added. This
functionality is especially useful when running COMMIT in a loop in
PL/pgSQL.

Reviewed-by: Fabien COELHO <coelho@cri.ensmp.fr>
Discussion: /messages/by-id/28536681-324b-10dc-ade8-ab46f7645a5a@2ndquadrant.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/280a408b48d5ee42969f981bceb9e9426c3a344c

Modified Files
--------------
doc/src/sgml/plpgsql.sgml | 14 ++
doc/src/sgml/ref/abort.sgml | 14 +-
doc/src/sgml/ref/commit.sgml | 23 ++-
doc/src/sgml/ref/end.sgml | 14 +-
doc/src/sgml/ref/rollback.sgml | 23 ++-
doc/src/sgml/spi.sgml | 29 +++-
src/backend/access/transam/xact.c | 73 +++++++-
src/backend/catalog/sql_features.txt | 2 +-
src/backend/executor/spi.c | 50 +++++-
src/backend/nodes/copyfuncs.c | 1 +
src/backend/nodes/equalfuncs.c | 1 +
src/backend/parser/gram.y | 19 +-
src/backend/tcop/utility.c | 4 +-
src/bin/psql/tab-complete.c | 8 +-
src/include/access/xact.h | 6 +-
src/include/executor/spi.h | 2 +
src/include/nodes/parsenodes.h | 1 +
.../plpgsql/src/expected/plpgsql_transaction.out | 28 +++
src/pl/plpgsql/src/pl_exec.c | 18 +-
src/pl/plpgsql/src/pl_funcs.c | 10 +-
src/pl/plpgsql/src/pl_gram.y | 18 +-
src/pl/plpgsql/src/pl_unreserved_kwlist.h | 2 +
src/pl/plpgsql/src/plpgsql.h | 2 +
src/pl/plpgsql/src/sql/plpgsql_transaction.sql | 23 +++
src/test/regress/expected/transactions.out | 191 +++++++++++++++++++++
src/test/regress/sql/transactions.sql | 63 +++++++
26 files changed, 601 insertions(+), 38 deletions(-)