Improve SP-GiST opclass API to better support unlabeled nodes

Enterprise / PostgreSQL - Tom Lane [sss.pgh.pa.us] - 23 August 2016 11:10 UTC

Previously, the spgSplitTuple action could only create a new upper tuple containing a single labeled node. This made it useless for opclasses that prefer to work with fixed sets of nodes (labeled or otherwise), which meant that restrictive prefixes could not be used with such node definitions. Change the output field set for the choose() method to allow it to specify any valid node set for the new upper tuple, and to specify which of these nodes to place the modified lower tuple in.

In addition to its primary use for fixed node sets, this feature could allow existing opclasses that use variable node sets to skip a separate spgAddNode action when splitting a tuple, by setting up the node needed for the incoming value as part of the spgSplitTuple action. However, care would have to be taken to add the extra node only when it would not make the tuple bigger than before. (spgAddNode can enlarge the tuple, spgSplitTuple can't.)

This is a prerequisite for an upcoming SP-GiST inet opclass, but is being committed separately to increase the visibility of the API change.

In passing, improve the documentation about the traverse-values feature that was added by commit ccd6eb49a.

Emre Hasegeli, with cosmetic adjustments and documentation rework by me

Discussion:

d2ddee6 Improve SP-GiST opclass API to better support unlabeled nodes.
doc/src/sgml/spgist.sgml | 115 +++++++++++++++++--------------
src/backend/access/spgist/spgdoinsert.c | 39 +++++++++--
src/backend/access/spgist/spgtextproc.c | 12 +++-
src/include/access/spgist.h | 12 ++--
4 files changed, 115 insertions(+), 63 deletions(-)

Upstream: git.postgresql.org


  • Share