pgsql: Create core infrastructure for KNNGIST.

Create core infrastructure for KNNGIST.

This is a heavily revised version of builtin_knngist_core-0.9.  The
ordering operators are no longer mixed in with actual quals, which would
have confused not only humans but significant parts of the planner.
Instead, ordering operators are carried separately throughout planning and
execution.

Since the API for ambeginscan and amrescan functions had to be changed
anyway, this commit takes the opportunity to rationalize that a bit.
RelationGetIndexScan no longer forces a premature index_rescan call;
instead, callers of index_beginscan must call index_rescan too.  Aside from
making the AM-side initialization logic a bit less peculiar, this has the
advantage that we do not make a useless extra am_rescan call when there are
runtime key values.  AMs formerly could not assume that the key values
passed to amrescan were actually valid; now they can.

Teodor Sigaev and Tom Lane

Branch
------
master

Details
-------
http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=d583f10b7e0b9e1ed18f339f3177ed42ac2f7570

Modified Files
--------------
doc/src/sgml/catalogs.sgml                 |    6 +-
doc/src/sgml/indexam.sgml                  |   69 +++++++----
src/backend/access/gin/ginscan.c           |   55 ++++----
src/backend/access/gist/gistscan.c         |   74 +++++------
src/backend/access/hash/hash.c             |   44 +++---
src/backend/access/index/genam.c           |   33 +++---
src/backend/access/index/indexam.c         |   42 ++++---
src/backend/access/nbtree/nbtree.c         |   39 +++---
src/backend/commands/cluster.c             |    4 +-
src/backend/commands/explain.c             |    2 +
src/backend/executor/execQual.c            |    2 +-
src/backend/executor/execUtils.c           |    4 +-
src/backend/executor/nodeBitmapIndexscan.c |   24 +++-
src/backend/executor/nodeIndexscan.c       |  160 ++++++++++++++++-------
src/backend/executor/nodeMergejoin.c       |    2 +-
src/backend/nodes/copyfuncs.c              |    2 +
src/backend/nodes/outfuncs.c               |    3 +
src/backend/optimizer/path/costsize.c      |   11 +-
src/backend/optimizer/path/indxpath.c      |  198 +++++++++++++++++++++++++++-
src/backend/optimizer/plan/createplan.c    |   86 +++++++++++-
src/backend/optimizer/plan/planner.c       |    2 +-
src/backend/optimizer/plan/setrefs.c       |    4 +
src/backend/optimizer/plan/subselect.c     |    5 +-
src/backend/optimizer/util/pathnode.c      |    6 +-
src/backend/utils/adt/selfuncs.c           |   93 ++++++++------
src/backend/utils/cache/lsyscache.c        |   31 ++++-
src/include/access/genam.h                 |   10 +-
src/include/access/relscan.h               |    6 +-
src/include/access/skey.h                  |    6 +
src/include/catalog/catversion.h           |    2 +-
src/include/catalog/pg_am.h                |    6 +-
src/include/catalog/pg_proc.h              |   16 +-
src/include/executor/nodeIndexscan.h       |    4 +-
src/include/nodes/execnodes.h              |   18 ++-
src/include/nodes/plannodes.h              |   19 +++-
src/include/nodes/relation.h               |    8 +
src/include/optimizer/cost.h               |    2 +-
src/include/optimizer/pathnode.h           |    1 +
src/include/pg_config_manual.h             |    2 +-
src/include/utils/lsyscache.h              |    3 +-
40 files changed, 790 insertions(+), 314 deletions(-)