pgsql: Buffering GiST index build algorithm.

Buffering GiST index build algorithm.

When building a GiST index that doesn't fit in cache, buffers are attached
to some internal nodes in the index. This speeds up the build by avoiding
random I/O that would otherwise be needed to traverse all the way down the
tree to the find right leaf page for tuple.

Alexander Korotkov

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/5edb24a8983e4a103e26153853d91141f818227c

Modified Files
--------------
doc/src/sgml/gist.sgml                     |   34 +
doc/src/sgml/ref/create_index.sgml         |   20 +
src/backend/access/common/reloptions.c     |   11 +
src/backend/access/gist/Makefile           |    2 +-
src/backend/access/gist/README             |  135 ++++
src/backend/access/gist/gist.c             |  211 +-----
src/backend/access/gist/gistbuild.c        | 1068 ++++++++++++++++++++++++++++
src/backend/access/gist/gistbuildbuffers.c |  787 ++++++++++++++++++++
src/backend/access/gist/gistutil.c         |   27 +-
src/backend/access/gist/gistxlog.c         |    6 +-
src/include/access/gist_private.h          |  182 +++++-
11 files changed, 2297 insertions(+), 186 deletions(-)