Line data    Source code

       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) 1996-2017, 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             : 
      48             : Datum
      49          27 : areasel(PG_FUNCTION_ARGS)
      50             : {
      51          27 :     PG_RETURN_FLOAT8(0.005);
      52             : }
      53             : 
      54             : Datum
      55           1 : areajoinsel(PG_FUNCTION_ARGS)
      56             : {
      57           1 :     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             : 
      67             : Datum
      68         117 : positionsel(PG_FUNCTION_ARGS)
      69             : {
      70         117 :     PG_RETURN_FLOAT8(0.1);
      71             : }
      72             : 
      73             : Datum
      74           3 : positionjoinsel(PG_FUNCTION_ARGS)
      75             : {
      76           3 :     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             : 
      86             : Datum
      87         139 : contsel(PG_FUNCTION_ARGS)
      88             : {
      89         139 :     PG_RETURN_FLOAT8(0.001);
      90             : }
      91             : 
      92             : Datum
      93           1 : contjoinsel(PG_FUNCTION_ARGS)
      94             : {
      95           1 :     PG_RETURN_FLOAT8(0.001);
      96             : }