int
main(int argc, char **argv)
{
int nuniv;
int nelem;
int ncombo, *elems, cnum, i;
Combinations vp;
if (argc != 3) {
printf("usage: %s nuniv nelem\n", argv[0]);
return 1;
}
nuniv = atoi(argv[1]);
nelem = atoi(argv[2]);
vp = init_combinations(nuniv, nelem);
if (vp == NULL) {
printf("init_combinations failed\n");
return 1;
}
ncombo = num_combinations(vp);
elems = (int *) malloc(nelem * sizeof(int));
for (cnum=0; cnum<ncombo; cnum++) {
get_combination(vp, cnum, elems);
for (i=0; i<nelem; i++)
printf("%d ", elems[i] + 1);
printf("\n");
}
free_combinations(vp);
return 0;
}
/*
* statext_ndistinct_build
* Compute ndistinct coefficient for the combination of attributes.
*
* This computes the ndistinct estimate using the same estimator used
* in analyze.c and then computes the coefficient.
*/
MVNDistinct *
statext_ndistinct_build(double totalrows, int numrows, HeapTuple *rows,
Bitmapset *attrs, VacAttrStats **stats)
{
MVNDistinct *result;
int k;
int itemcnt;
int numattrs = bms_num_members(attrs);
int numcombs = num_combinations(numattrs);
result = palloc(offsetof(MVNDistinct, items) +
numcombs * sizeof(MVNDistinctItem));
result->magic = STATS_NDISTINCT_MAGIC;
result->type = STATS_NDISTINCT_TYPE_BASIC;
result->nitems = numcombs;
itemcnt = 0;
for (k = 2; k <= numattrs; k++)
{
int *combination;
CombinationGenerator *generator;
/* generate combinations of K out of N elements */
generator = generator_init(numattrs, k);
while ((combination = generator_next(generator)))
{
MVNDistinctItem *item = &result->items[itemcnt];
int j;
item->attrs = NULL;
for (j = 0; j < k; j++)
item->attrs = bms_add_member(item->attrs,
stats[combination[j]]->attr->attnum);
item->ndistinct =
ndistinct_for_combination(totalrows, numrows, rows,
stats, k, combination);
itemcnt++;
Assert(itemcnt <= result->nitems);
}
generator_free(generator);
}
/* must consume exactly the whole output array */
Assert(itemcnt == result->nitems);
return result;
}
