1/*-------------------------------------------------------------------------
2 *
3 * geo_selfuncs.c
4 * Selectivity routines registered in the operator catalog in the
5 * "oprrest" and "oprjoin" attributes.
6 *
7 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
8 * Portions Copyright (c) 1994, Regents of the University of California
9 *
10 *
11 * IDENTIFICATION
12 * src/backend/utils/adt/geo_selfuncs.c
13 *
14 * XXX These are totally bogus. Perhaps someone will make them do
15 * something reasonable, someday.
16 *
17 *-------------------------------------------------------------------------
18 */
19#include "postgres.h"
20
21#include "utils/builtins.h"
22#include "utils/geo_decls.h"
23
24
25/*
26 * Selectivity functions for geometric operators. These are bogus -- unless
27 * we know the actual key distribution in the index, we can't make a good
28 * prediction of the selectivity of these operators.
29 *
30 * Note: the values used here may look unreasonably small. Perhaps they
31 * are. For now, we want to make sure that the optimizer will make use
32 * of a geometric index if one is available, so the selectivity had better
33 * be fairly small.
34 *
35 * In general, GiST needs to search multiple subtrees in order to guarantee
36 * that all occurrences of the same key have been found. Because of this,
37 * the estimated cost for scanning the index ought to be higher than the
38 * output selectivity would indicate. gistcostestimate(), over in selfuncs.c,
39 * ought to be adjusted accordingly --- but until we can generate somewhat
40 * realistic numbers here, it hardly matters...
41 */
42
43
44/*
45 * Selectivity for operators that depend on area, such as "overlap".
46 */
47
48Datum
49areasel(PG_FUNCTION_ARGS)
50{
51 PG_RETURN_FLOAT8(0.005);
52}
53
54Datum
55areajoinsel(PG_FUNCTION_ARGS)
56{
57 PG_RETURN_FLOAT8(0.005);
58}
59
60/*
61 * positionsel
62 *
63 * How likely is a box to be strictly left of (right of, above, below)
64 * a given box?
65 */
66
67Datum
68positionsel(PG_FUNCTION_ARGS)
69{
70 PG_RETURN_FLOAT8(0.1);
71}
72
73Datum
74positionjoinsel(PG_FUNCTION_ARGS)
75{
76 PG_RETURN_FLOAT8(0.1);
77}
78
79/*
80 * contsel -- How likely is a box to contain (be contained by) a given box?
81 *
82 * This is a tighter constraint than "overlap", so produce a smaller
83 * estimate than areasel does.
84 */
85
86Datum
87contsel(PG_FUNCTION_ARGS)
88{
89 PG_RETURN_FLOAT8(0.001);
90}
91
92Datum
93contjoinsel(PG_FUNCTION_ARGS)
94{
95 PG_RETURN_FLOAT8(0.001);
96}
97