From 8a31acd642b7802f51066f476225725e68a91d52 Mon Sep 17 00:00:00 2001
From: Sandro Santilli <strk@keybit.net>
Date: Fri, 20 Jan 2012 08:12:15 +0000
Subject: [PATCH] Change ST_Equals to use the ~= operator (#1453)

Doing so it will consistently return TRUE for EMPTY-EMPTY, while
previously _ST_Equals returned TRUE but ST_Equals returned FALSE.

The commit also changes signature of the C function
from 'geomequals' to 'ST_Equals' and marks an SQL 'Equals'
signature as a candidate for dropping before 2.0.0 final

git-svn-id: http://svn.osgeo.org/postgis/trunk@8886 b70326c6-7e19-0410-871a-916f4a2858ee
---
 postgis/lwgeom_geos.c    | 8 +++++---
 postgis/postgis.sql.in.c | 7 ++++---
 regress/empty.sql        | 4 ++++
 regress/empty_expected   | 1 +
 4 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/postgis/lwgeom_geos.c b/postgis/lwgeom_geos.c
index ce214ca34..c966fea32 100644
--- a/postgis/lwgeom_geos.c
+++ b/postgis/lwgeom_geos.c
@@ -65,7 +65,7 @@ Datum geomunion(PG_FUNCTION_ARGS);
 Datum ST_UnaryUnion(PG_FUNCTION_ARGS);
 Datum issimple(PG_FUNCTION_ARGS);
 Datum isring(PG_FUNCTION_ARGS);
-Datum geomequals(PG_FUNCTION_ARGS);
+Datum ST_Equals(PG_FUNCTION_ARGS);
 Datum pointonsurface(PG_FUNCTION_ARGS);
 Datum GEOSnoop(PG_FUNCTION_ARGS);
 Datum postgis_geos_version(PG_FUNCTION_ARGS);
@@ -2959,8 +2959,8 @@ Datum relate_full(PG_FUNCTION_ARGS)
 }
 
 
-PG_FUNCTION_INFO_V1(geomequals);
-Datum geomequals(PG_FUNCTION_ARGS)
+PG_FUNCTION_INFO_V1(ST_Equals);
+Datum ST_Equals(PG_FUNCTION_ARGS)
 {
 	GSERIALIZED *geom1;
 	GSERIALIZED *geom2;
@@ -2981,6 +2981,8 @@ Datum geomequals(PG_FUNCTION_ARGS)
 	/*
 	 * short-circuit: Loose test, if geom2 bounding box does not overlap
 	 * geom1 bounding box we can prematurely return FALSE.
+	 *
+	 * TODO: use gbox_same_2d instead (not available at time of writing)
 	 */
 	if ( gserialized_get_gbox_p(geom1, &box1) &&
 	     gserialized_get_gbox_p(geom2, &box2) )
diff --git a/postgis/postgis.sql.in.c b/postgis/postgis.sql.in.c
index 136b5e828..35a9356aa 100644
--- a/postgis/postgis.sql.in.c
+++ b/postgis/postgis.sql.in.c
@@ -3208,22 +3208,23 @@ CREATE OR REPLACE FUNCTION ST_IsCollection(geometry)
 	LANGUAGE 'C' IMMUTABLE STRICT;
 
 -- Deprecation in 1.2.3
+-- TODO: drop in 2.0.0 !
 CREATE OR REPLACE FUNCTION Equals(geom1 geometry, geom2 geometry)
 	RETURNS boolean
-	AS 'MODULE_PATHNAME','geomequals'
+	AS 'MODULE_PATHNAME','ST_Equals'
 	LANGUAGE 'C' IMMUTABLE STRICT;
 
 -- Availability: 1.5.0
 CREATE OR REPLACE FUNCTION _ST_Equals(geom1 geometry, geom2 geometry)
 	RETURNS boolean
-	AS 'MODULE_PATHNAME','geomequals'
+	AS 'MODULE_PATHNAME','ST_Equals'
 	LANGUAGE 'C' IMMUTABLE STRICT
 	COST 100;
 
 -- Availability: 1.2.1
 CREATE OR REPLACE FUNCTION ST_Equals(geom1 geometry, geom2 geometry)
 	RETURNS boolean
-	AS 'SELECT $1 && $2 AND _ST_Equals($1,$2)'
+	AS 'SELECT $1 ~= $2 AND _ST_Equals($1,$2)'
 	LANGUAGE 'SQL' IMMUTABLE;
 
 
diff --git a/regress/empty.sql b/regress/empty.sql
index 0e8d65435..f7f47725b 100644
--- a/regress/empty.sql
+++ b/regress/empty.sql
@@ -98,6 +98,10 @@ WITH inp AS (SELECT
  'POLYGON EMPTY'::geometry as empty,
  'POLYGON((0 0, 10 0, 5 5, 0 0))'::geometry as geometry
  ) SELECT 'ST_Disjoint(geometry, empty) == TRUE', ST_Disjoint(geometry, empty) FROM inp;
+WITH inp AS (SELECT
+ 'POLYGON EMPTY'::geometry as empty1,
+ 'POINT Z EMPTY'::geometry as empty2
+ ) SELECT 'ST_Equals(empty1, empty2) == TRUE', ST_Equals(empty1, empty2) FROM inp;
 WITH inp AS (SELECT
  'POLYGON EMPTY'::geometry as empty
  ) SELECT 'ST_IsSimple(empty) == TRUE', ST_IsSimple(empty) FROM inp;
diff --git a/regress/empty_expected b/regress/empty_expected
index ad42a04d8..cf8d4f431 100644
--- a/regress/empty_expected
+++ b/regress/empty_expected
@@ -40,6 +40,7 @@ ST_Intersects(geometry, empty) == FALSE|f
 ST_Intersects(empty, empty) == FALSE|f
 ST_Disjoint(empty, empty) == TRUE|t
 ST_Disjoint(geometry, empty) == TRUE|t
+ST_Equals(empty1, empty2) == TRUE|t
 ST_IsSimple(empty) == TRUE|t
 ST_IsValid(empty) == TRUE|t
 ST_NumGeometries(empty) == 0|0
-- 
2.40.0