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Allow GiST distance function to return merely a lower-bound.

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The distance function can now set *recheck = false, like index quals. The
executor will then re-check the ORDER BY expressions, and use a queue to
reorder the results on the fly.

This makes it possible to do kNN-searches on polygons and circles, which
don't store the exact value in the index, but just a bounding box.

Alexander Korotkov and me
This commit is contained in:
Heikki Linnakangas
2015-05-15 14:26:51 +03:00
parent ecd222e770
commit 35fcb1b3d0
19 changed files with 699 additions and 40 deletions
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27
src/backend/utils/adt/geo_ops.c
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@@ -2657,6 +2657,18 @@ dist_ppoly(PG_FUNCTION_ARGS)
PG_RETURN_FLOAT8(result);
}
Datum
dist_polyp(PG_FUNCTION_ARGS)
{
POLYGON *poly = PG_GETARG_POLYGON_P(0);
Point *point = PG_GETARG_POINT_P(1);
float8 result;
result = dist_ppoly_internal(point, poly);
PG_RETURN_FLOAT8(result);
}
static double
dist_ppoly_internal(Point *pt, POLYGON *poly)
{
@@ -5112,6 +5124,21 @@ dist_pc(PG_FUNCTION_ARGS)
PG_RETURN_FLOAT8(result);
}
/*
* Distance from a circle to a point
*/
Datum
dist_cpoint(PG_FUNCTION_ARGS)
{
CIRCLE *circle = PG_GETARG_CIRCLE_P(0);
Point *point = PG_GETARG_POINT_P(1);
float8 result;
result = point_dt(point, &circle->center) - circle->radius;
if (result < 0)
result = 0;
PG_RETURN_FLOAT8(result);
}
/* circle_center - returns the center point of the circle.
*/