From: Paul Ramsey <pramsey@cleverelephant.ca>
Date: Mon, 14 Sep 2009 18:33:54 +0000 (+0000)
Subject: Crib index penalty tweak from pgsphere.
X-Git-Tag: 1.5.0b1~511
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=06568b44d1279afd38f36d02890e232a71314377;p=postgis

Crib index penalty tweak from pgsphere.


git-svn-id: http://svn.osgeo.org/postgis/trunk@4497 b70326c6-7e19-0410-871a-916f4a2858ee
---

diff --git a/liblwgeom/liblwgeom.h b/liblwgeom/liblwgeom.h
index 86230b99f..b16609ab9 100644
--- a/liblwgeom/liblwgeom.h
+++ b/liblwgeom/liblwgeom.h
@@ -39,12 +39,14 @@
 #define INTEGRITY_CHECKS 1
 
 /*
- * Floating point comparitors.
- */
+** Floating point comparitors.
+*/
 #define FP_TOLERANCE 1e-12
+#define FP_ZERO(A) (fabs(A) <= FP_TOLERANCE)
 #define FP_MAX(A, B) (((A) > (B)) ? (A) : (B))
 #define FP_MIN(A, B) (((A) < (B)) ? (A) : (B))
-#define FP_EQUALS(A, B) (fabs((A)-(B)) < FP_TOLERANCE)
+#define FP_EQUALS(A, B) (fabs((A)-(B)) <= FP_TOLERANCE)
+#define FP_NEQUALS(A, B) (fabs((A)-(B)) > FP_TOLERANCE)
 #define FP_LT(A, B) (((A) + FP_TOLERANCE) < (B))
 #define FP_LTEQ(A, B) (((A) - FP_TOLERANCE) <= (B))
 #define FP_GT(A, B) (((A) - FP_TOLERANCE) > (B))
@@ -54,6 +56,10 @@
 #define FP_CONTAINS_INCL(A, X, B) (FP_LTEQ(A, X) && FP_LTEQ(X, B))
 #define FP_CONTAINS_EXCL(A, X, B) (FP_LT(A, X) && FP_LT(X, B))
 #define FP_CONTAINS(A, X, B) FP_CONTAINS_EXCL(A, X, B)
+
+/*
+** Utility true and false defines.
+*/
 #define LW_TRUE 1
 #define LW_FALSE 0
 
diff --git a/postgis/geography_gist.c b/postgis/geography_gist.c
index 723329239..2e764595a 100644
--- a/postgis/geography_gist.c
+++ b/postgis/geography_gist.c
@@ -830,6 +830,16 @@ Datum geography_gist_penalty(PG_FUNCTION_ARGS)
 	size_union = gidx_union_volume(gbox_index_orig, gbox_index_new);
 	size_orig = gidx_volume(gbox_index_orig);
 	*result = size_union - size_orig;
+
+	/* All things being equal, we prefer to expand small boxes rather than large boxes. */
+	if( FP_ZERO(*result) )
+		if( FP_ZERO(size_orig) )
+			*result = 0.0;
+		else
+			*result = 1.0 - (1.0/(1.0 + size_orig));
+	else
+		*result += 1;
+
 	POSTGIS_DEBUGF(4, "[GIST] union size (%f), original size (%f), penalty (%f)", size_union, size_orig, *result);
 	PG_RETURN_POINTER(result);
 }