pgsql: Allow GiST distance function to return merely a lower-bound.

Allow GiST distance function to return merely a lower-bound.

The distance function can now set *recheck = false, like index quals. The
executor will then re-check the ORDER BY expressions, and use a queue to
reorder the results on the fly.

This makes it possible to do kNN-searches on polygons and circles, which
don't store the exact value in the index, but just a bounding box.

Alexander Korotkov and me

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/35fcb1b3d038a501f3f4c87c05630095abaaadab

Modified Files
--------------
doc/src/sgml/gist.sgml | 35 ++-
src/backend/access/gist/gistget.c | 30 ++-
src/backend/access/gist/gistproc.c | 37 +++
src/backend/access/gist/gistscan.c | 5 +
src/backend/executor/nodeIndexscan.c | 379 +++++++++++++++++++++++++++-
src/backend/optimizer/plan/createplan.c | 73 ++++--
src/backend/utils/adt/geo_ops.c | 27 ++
src/include/access/genam.h | 3 +
src/include/access/relscan.h | 9 +
src/include/catalog/catversion.h | 2 +-
src/include/catalog/pg_amop.h | 2 +
src/include/catalog/pg_amproc.h | 2 +
src/include/catalog/pg_operator.h | 8 +-
src/include/catalog/pg_proc.h | 4 +
src/include/nodes/execnodes.h | 20 ++
src/include/nodes/plannodes.h | 10 +-
src/include/utils/geo_decls.h | 3 +
src/test/regress/expected/create_index.out | 78 ++++++
src/test/regress/sql/create_index.sql | 12 +
19 files changed, 699 insertions(+), 40 deletions(-)