pgsql: Refactor cluster_rel() to handle more options

Refactor cluster_rel() to handle more options

This extends cluster_rel() in such a way that more options can be added
in the future, which will reduce the amount of chunk code for an
upcoming SKIP_LOCKED aimed for VACUUM.  As VACUUM FULL is a different
flavor of CLUSTER, we want to make that extensible to ease integration.

This only reworks the API and its callers, without providing anything
user-facing.  Two options are present now: verbose mode and relation
recheck when doing the cluster command work across multiple
transactions.  This could be used as well as a base to extend the
grammar of CLUSTER later on.

Author: Michael Paquier
Reviewed-by: Nathan Bossart
Discussion: https://postgr.es/m/20180723031058.GE2854@paquier.xyz

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/9ebe0572ceab69c57811746ead2d3418daea8673

Modified Files
--------------
src/backend/commands/cluster.c   |  9 ++++++---
src/backend/commands/vacuum.c    |  8 ++++++--
src/backend/nodes/copyfuncs.c    |  2 +-
src/backend/nodes/equalfuncs.c   |  2 +-
src/backend/parser/gram.y        | 12 +++++++++---
src/include/commands/cluster.h   |  3 +--
src/include/nodes/parsenodes.h   |  8 +++++++-
src/tools/pgindent/typedefs.list |  1 +
8 files changed, 32 insertions(+), 13 deletions(-)