From b0f2d681bdfd6a5b3e90d092f9d924f943b4fc5f Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Wed, 10 Nov 2010 16:51:39 -0500 Subject: [PATCH] Fix line_construct_pm() for the case of "infinite" (DBL_MAX) slope. This code was just plain wrong: what you got was not a line through the given point but a line almost indistinguishable from the Y-axis, although not truly vertical. The only caller that tries to use this function with m == DBL_MAX is dist_ps_internal for the case where the lseg is horizontal; it would end up producing the distance from the given point to the place where the lseg's line crosses the Y-axis. That function is used by other operators too, so there are several operators that could compute wrong distances from a line segment to something else. Per bug #5745 from jindiax. Back-patch to all supported branches. --- src/backend/utils/adt/geo_ops.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/src/backend/utils/adt/geo_ops.c b/src/backend/utils/adt/geo_ops.c index f3b6a389ff..8a99df1356 100644 --- a/src/backend/utils/adt/geo_ops.c +++ b/src/backend/utils/adt/geo_ops.c @@ -1072,13 +1072,20 @@ line_construct_pm(Point *pt, double m) { LINE *result = (LINE *) palloc(sizeof(LINE)); - /* use "mx - y + yinter = 0" */ - result->A = m; - result->B = -1.0; if (m == DBL_MAX) - result->C = pt->y; + { + /* vertical - use "x = C" */ + result->A = -1; + result->B = 0; + result->C = pt->x; + } else + { + /* use "mx - y + yinter = 0" */ + result->A = m; + result->B = -1.0; result->C = pt->y - m * pt->x; + } #ifdef NOT_USED result->m = m;