text: /*
   * contrib/btree_gist/btree_enum.c
   */
  #include "postgres.h"
  #include "fmgr.h"
  #include "utils/builtins.h"
  
  #include "btree_gist.h"
  #include "btree_utils_num.h"
  
  /* enums are really Oids, so we just use the same structure */
  
  typedef struct
  {
      Oid            lower;
      Oid            upper;
  } oidKEY;
  
  /*
  ** enum ops
  */
  PG_FUNCTION_INFO_V1(gbt_enum_compress);
  PG_FUNCTION_INFO_V1(gbt_enum_fetch);
  PG_FUNCTION_INFO_V1(gbt_enum_union);
  PG_FUNCTION_INFO_V1(gbt_enum_picksplit);
  PG_FUNCTION_INFO_V1(gbt_enum_consistent);
  PG_FUNCTION_INFO_V1(gbt_enum_penalty);
  PG_FUNCTION_INFO_V1(gbt_enum_same);
  
  
  static bool
  gbt_enumgt(const void *a, const void *b, FmgrInfo *flinfo)
  {
      return DatumGetBool(
                          CallerFInfoFunctionCall2(enum_gt, flinfo, InvalidOid, ObjectIdGetDatum(*((const Oid *) a)), ObjectIdGetDatum(*((const Oid *) b)))
          );
  }
  static bool
  gbt_enumge(const void *a, const void *b, FmgrInfo *flinfo)
  {
      return DatumGetBool(
                          CallerFInfoFunctionCall2(enum_ge, flinfo, InvalidOid, ObjectIdGetDatum(*((const Oid *) a)), ObjectIdGetDatum(*((const Oid *) b)))
          );
  }
  static bool
  gbt_enumeq(const void *a, const void *b, FmgrInfo *flinfo)
  {
      return (*((const Oid *) a) == *((const Oid *) b));
  }
  static bool
  gbt_enumle(const void *a, const void *b, FmgrInfo *flinfo)
  {
      return DatumGetBool(
                          CallerFInfoFunctionCall2(enum_le, flinfo, InvalidOid, ObjectIdGetDatum(*((const Oid *) a)), ObjectIdGetDatum(*((const Oid *) b)))
          );
  }
  static bool
  gbt_enumlt(const void *a, const void *b, FmgrInfo *flinfo)
  {
      return DatumGetBool(
                          CallerFInfoFunctionCall2(enum_lt, flinfo, InvalidOid, ObjectIdGetDatum(*((const Oid *) a)), ObjectIdGetDatum(*((const Oid *) b)))
          );
  }
  
  static int
  gbt_enumkey_cmp(const void *a, const void *b, FmgrInfo *flinfo)
  {
      oidKEY       *ia = (oidKEY *) (((const Nsrt *) a)->t);
      oidKEY       *ib = (oidKEY *) (((const Nsrt *) b)->t);
  
      if (ia->lower == ib->lower)
      {
          if (ia->upper == ib->upper)
              return 0;
  
          return DatumGetInt32(
                               CallerFInfoFunctionCall2(enum_cmp, flinfo, InvalidOid, ObjectIdGetDatum(ia->upper), ObjectIdGetDatum(ib->upper))
              );
      }
  
      return DatumGetInt32(
                           CallerFInfoFunctionCall2(enum_cmp, flinfo, InvalidOid, ObjectIdGetDatum(ia->lower), ObjectIdGetDatum(ib->lower))
          );
  }
  
  static const gbtree_ninfo tinfo =
  {
      gbt_t_enum,
      sizeof(Oid),
      8,                            /* sizeof(gbtreekey8) */
      gbt_enumgt,
      gbt_enumge,
      gbt_enumeq,
      gbt_enumle,
      gbt_enumlt,
      gbt_enumkey_cmp,
      NULL                        /* no KNN support at least for now */
  };
  
  
  /**************************************************
   * Enum ops
   **************************************************/
  
  
  Datum
  gbt_enum_compress(PG_FUNCTION_ARGS)
  {
      GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
  
      PG_RETURN_POINTER(gbt_num_compress(entry, &tinfo));
  }
  
  Datum
  gbt_enum_fetch(PG_FUNCTION_ARGS)
  {
      GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
  
      PG_RETURN_POINTER(gbt_num_fetch(entry, &tinfo));
  }
  
  Datum
  gbt_enum_consistent(PG_FUNCTION_ARGS)
  {
      GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
      Oid            query = PG_GETARG_OID(1);
      StrategyNumber strategy = (StrategyNumber) PG_GETARG_UINT16(2);
  
      /* Oid        subtype = PG_GETARG_OID(3); */
      bool       *recheck = (bool *) PG_GETARG_POINTER(4);
      oidKEY       *kkk = (oidKEY *) DatumGetPointer(entry->key);
      GBT_NUMKEY_R key;
  
      /* All cases served by this function are exact */
      *recheck = false;
  
      key.lower = (GBT_NUMKEY *) &kkk->lower;
      key.upper = (GBT_NUMKEY *) &kkk->upper;
  
      PG_RETURN_BOOL(
                     gbt_num_consistent(&key, (void *) &query, &strategy, GIST_LEAF(entry), &tinfo, fcinfo->flinfo)
          );
  }
  
  Datum
  gbt_enum_union(PG_FUNCTION_ARGS)
  {
      GistEntryVector *entryvec = (GistEntryVector *) PG_GETARG_POINTER(0);
      void       *out = palloc(sizeof(oidKEY));
  
      *(int *) PG_GETARG_POINTER(1) = sizeof(oidKEY);
      PG_RETURN_POINTER(gbt_num_union((void *) out, entryvec, &tinfo, fcinfo->flinfo));
  }
  
  
  Datum
  gbt_enum_penalty(PG_FUNCTION_ARGS)
  {
      oidKEY       *origentry = (oidKEY *) DatumGetPointer(((GISTENTRY *) PG_GETARG_POINTER(0))->key);
      oidKEY       *newentry = (oidKEY *) DatumGetPointer(((GISTENTRY *) PG_GETARG_POINTER(1))->key);
      float       *result = (float *) PG_GETARG_POINTER(2);
  
      penalty_num(result, origentry->lower, origentry->upper, newentry->lower, newentry->upper);
  
      PG_RETURN_POINTER(result);
  }
  
  Datum
  gbt_enum_picksplit(PG_FUNCTION_ARGS)
  {
      PG_RETURN_POINTER(gbt_num_picksplit(
                                          (GistEntryVector *) PG_GETARG_POINTER(0),
                                          (GIST_SPLITVEC *) PG_GETARG_POINTER(1),
                                          &tinfo, fcinfo->flinfo
                                          ));
  }
  
  Datum
  gbt_enum_same(PG_FUNCTION_ARGS)
  {
      oidKEY       *b1 = (oidKEY *) PG_GETARG_POINTER(0);
      oidKEY       *b2 = (oidKEY *) PG_GETARG_POINTER(1);
      bool       *result = (bool *) PG_GETARG_POINTER(2);
  
      *result = gbt_num_same((void *) b1, (void *) b2, &tinfo, fcinfo->flinfo);
      PG_RETURN_POINTER(result);
  }
  