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Fix line_construct_pm() for the case of "infinite" (DBL_MAX) slope.

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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.
This commit is contained in:
Tom Lane 2010-11-10 16:51:39 -05:00
parent 55425d3721
commit 90e8efa338
1 changed files with 11 additions and 4 deletions
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13
src/backend/utils/adt/geo_ops.c
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@ -1070,13 +1070,20 @@ line_construct_pm(Point *pt, double m)
{
LINE *result = (LINE *) palloc(sizeof(LINE));
if (m == DBL_MAX)
{
/* 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;
if (m == DBL_MAX)
result->C = pt->y;
else
result->C = pt->y - m * pt->x;
}
#ifdef NOT_USED
result->m = m;