geography_distance_knn()

Datum geography_distance_knn

(

PG_FUNCTION_ARGS

)

Definition at line 71 of file geography_measurement.c.

{
        LWGEOM *lwgeom1 = NULL;
        LWGEOM *lwgeom2 = NULL;
        GSERIALIZED *g1 = NULL;
        GSERIALIZED *g2 = NULL;
        double distance;
        double tolerance = FP_TOLERANCE;
        bool use_spheroid = false; /* must use sphere, can't get index to harmonize with spheroid */
        SPHEROID s;
 
        /* Get our geometry objects loaded into memory. */
        g1 = PG_GETARG_GSERIALIZED_P(0);
        g2 = PG_GETARG_GSERIALIZED_P(1);
 
        gserialized_error_if_srid_mismatch(g1, g2, __func__);
 
        /* Initialize spheroid */
        spheroid_init_from_srid(fcinfo, gserialized_get_srid(g1), &s);
 
        /* Set to sphere if requested */
        if ( ! use_spheroid )
                s.a = s.b = s.radius;
 
        lwgeom1 = lwgeom_from_gserialized(g1);
        lwgeom2 = lwgeom_from_gserialized(g2);
 
        /* Return NULL on empty arguments. */
        if ( lwgeom_is_empty(lwgeom1) || lwgeom_is_empty(lwgeom2) )
        {
                PG_FREE_IF_COPY(g1, 0);
                PG_FREE_IF_COPY(g2, 1);
                PG_RETURN_NULL();
        }
 
        /* Make sure we have boxes attached */
        lwgeom_add_bbox_deep(lwgeom1, NULL);
        lwgeom_add_bbox_deep(lwgeom2, NULL);
 
        distance = lwgeom_distance_spheroid(lwgeom1, lwgeom2, &s, tolerance);
 
        POSTGIS_DEBUGF(2, "[GIST] '%s' got distance %g", __func__, distance);
 
        /* Clean up */
        lwgeom_free(lwgeom1);
        lwgeom_free(lwgeom2);
        PG_FREE_IF_COPY(g1, 0);
        PG_FREE_IF_COPY(g2, 1);
 
        /* Something went wrong, negative return... should already be eloged, return NULL */
        if ( distance < 0.0 )
        {
                PG_RETURN_NULL();
        }
 
        PG_RETURN_FLOAT8(distance);
}

References distance(), FP_TOLERANCE, gserialized_error_if_srid_mismatch(), gserialized_get_srid(), lwgeom_add_bbox_deep(), lwgeom_distance_spheroid(), lwgeom_free(), lwgeom_from_gserialized(), lwgeom_is_empty(), and s.

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