Add an in-core GiST index opclass for inet/cidr types.

This operator class can accelerate subnet/supernet tests as well as
btree-equivalent ordered comparisons.  It also handles a new network
operator inet && inet (overlaps, a/k/a "is supernet or subnet of"),
which is expected to be useful in exclusion constraints.

Ideally this opclass would be the default for GiST with inet/cidr data,
but we can't mark it that way until we figure out how to do a more or
less graceful transition from the current situation, in which the
really-completely-bogus inet/cidr opclasses in contrib/btree_gist are
marked as default.  Having the opclass in core and not default is better
than not having it at all, though.

While at it, add new documentation sections to allow us to officially
document GiST/GIN/SP-GiST opclasses, something there was never a clear
place to do before.  I filled these in with some simple tables listing
the existing opclasses and the operators they support, but there's
certainly scope to put more information there.

Emre Hasegeli, reviewed by Andreas Karlsson, further hacking by me

1 files changed, 1 insertions, 0 deletions

diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 720c8318011..5907cb13fd3 100644
--- a/src/include/utils/builtins.h
+++ b/src/include/utils/builtins.h
@@ -906,6 +906,7 @@ extern Datum network_sub(PG_FUNCTION_ARGS);
 extern Datum network_subeq(PG_FUNCTION_ARGS);
 extern Datum network_sup(PG_FUNCTION_ARGS);
 extern Datum network_supeq(PG_FUNCTION_ARGS);
+extern Datum network_overlap(PG_FUNCTION_ARGS);
 extern Datum network_network(PG_FUNCTION_ARGS);
 extern Datum network_netmask(PG_FUNCTION_ARGS);
 extern Datum network_hostmask(PG_FUNCTION_ARGS);