PostGIS  2.5.7dev-r@@SVN_REVISION@@

◆ geography_distance_knn()

Datum geography_distance_knn ( PG_FUNCTION_ARGS  )

Definition at line 70 of file geography_measurement.c.

71 {
72  LWGEOM *lwgeom1 = NULL;
73  LWGEOM *lwgeom2 = NULL;
74  GSERIALIZED *g1 = NULL;
75  GSERIALIZED *g2 = NULL;
76  double distance;
77  double tolerance = FP_TOLERANCE;
78  bool use_spheroid = false; /* must use sphere, can't get index to harmonize with spheroid */
79  SPHEROID s;
80 
81  /* Get our geometry objects loaded into memory. */
82  g1 = PG_GETARG_GSERIALIZED_P(0);
83  g2 = PG_GETARG_GSERIALIZED_P(1);
84 
85  /* Initialize spheroid */
86  spheroid_init_from_srid(fcinfo, gserialized_get_srid(g1), &s);
87 
88  error_if_srid_mismatch(gserialized_get_srid(g1), gserialized_get_srid(g2));
89 
90  /* Set to sphere if requested */
91  if ( ! use_spheroid )
92  s.a = s.b = s.radius;
93 
94  lwgeom1 = lwgeom_from_gserialized(g1);
95  lwgeom2 = lwgeom_from_gserialized(g2);
96 
97  /* Return NULL on empty arguments. */
98  if ( lwgeom_is_empty(lwgeom1) || lwgeom_is_empty(lwgeom2) )
99  {
100  PG_FREE_IF_COPY(g1, 0);
101  PG_FREE_IF_COPY(g2, 1);
102  PG_RETURN_NULL();
103  }
104 
105  /* Make sure we have boxes attached */
106  lwgeom_add_bbox_deep(lwgeom1, NULL);
107  lwgeom_add_bbox_deep(lwgeom2, NULL);
108 
109  distance = lwgeom_distance_spheroid(lwgeom1, lwgeom2, &s, tolerance);
110 
111  POSTGIS_DEBUGF(2, "[GIST] '%s' got distance %g", __func__, distance);
112 
113  /* Clean up */
114  lwgeom_free(lwgeom1);
115  lwgeom_free(lwgeom2);
116  PG_FREE_IF_COPY(g1, 0);
117  PG_FREE_IF_COPY(g2, 1);
118 
119  /* Something went wrong, negative return... should already be eloged, return NULL */
120  if ( distance < 0.0 )
121  {
122  PG_RETURN_NULL();
123  }
124 
125  PG_RETURN_FLOAT8(distance);
126 }
s
char * s
Definition: cu_in_wkt.c:23
gserialized_get_srid
int32_t gserialized_get_srid(const GSERIALIZED *s)
Extract the SRID from the serialized form (it is packed into three bytes so this is a handy function)...
Definition: g_serialized.c:100
lwgeom_from_gserialized
LWGEOM * lwgeom_from_gserialized(const GSERIALIZED *g)
Allocate a new LWGEOM from a GSERIALIZED.
Definition: g_serialized.c:1530
lwgeom_distance_spheroid
double lwgeom_distance_spheroid(const LWGEOM *lwgeom1, const LWGEOM *lwgeom2, const SPHEROID *spheroid, double tolerance)
Calculate the geodetic distance from lwgeom1 to lwgeom2 on the spheroid.
Definition: lwgeodetic.c:2187
lwgeom_free
void lwgeom_free(LWGEOM *geom)
Definition: lwgeom.c:1144
lwgeom_is_empty
int lwgeom_is_empty(const LWGEOM *geom)
Return true or false depending on whether a geometry is an "empty" geometry (no vertices members)
Definition: lwgeom.c:1393
lwgeom_add_bbox_deep
void lwgeom_add_bbox_deep(LWGEOM *lwgeom, GBOX *gbox)
Compute a box for geom and all sub-geometries, if not already computed.
Definition: lwgeom.c:705
error_if_srid_mismatch
void error_if_srid_mismatch(int srid1, int srid2)
Definition: lwutil.c:338
FP_TOLERANCE
#define FP_TOLERANCE
Floating point comparators.
Definition: liblwgeom_internal.h:53
distance
Datum distance(PG_FUNCTION_ARGS)
Definition: lwgeom_backend_api.c:199

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

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