Simplify box_overlap computations.

Given the assumption that a box's high coordinates are not less than its
low coordinates, the tests in box_ov() are overly complicated and can be
reduced to about half as much work.  Since many other functions in
geo_ops.c rely on that assumption, there doesn't seem to be a good reason
not to use it here.

Per discussion of Alexander Korotkov's GiST fix, which was already using
the simplified logic (in a non-fuzzy form, but the equivalence holds just
as well for fuzzy).

diff --git a/src/backend/utils/adt/geo_ops.c b/src/backend/utils/adt/geo_ops.c
index c899e80b35a96396dcd551c55d3d504ee475e356..ad18cf07e7d78956ce8db4b94d56cb50c3d4cad2 100644 (file)
--- a/src/backend/utils/adt/geo_ops.c
+++ b/src/backend/utils/adt/geo_ops.c
@@ -558,15 +558,10 @@ box_overlap(PG_FUNCTION_ARGS)
 static bool
 box_ov(BOX *box1, BOX *box2)
 {
-   return ((FPge(box1->high.x, box2->high.x) &&
-            FPle(box1->low.x, box2->high.x)) ||
-           (FPge(box2->high.x, box1->high.x) &&
-            FPle(box2->low.x, box1->high.x)))
-       &&
-       ((FPge(box1->high.y, box2->high.y) &&
-         FPle(box1->low.y, box2->high.y)) ||
-        (FPge(box2->high.y, box1->high.y) &&
-         FPle(box2->low.y, box1->high.y)));
+   return (FPle(box1->low.x, box2->high.x) &&
+           FPle(box2->low.x, box1->high.x) &&
+           FPle(box1->low.y, box2->high.y) &&
+           FPle(box2->low.y, box1->high.y));
 }
 
 /*     box_left        -       is box1 strictly left of box2?