Datum pg_kll_float_sketch_get_histogram()

in src/kll_float_sketch_pg_functions.c [425:470]

• 36 lines of code
• 4 McCabe index (conditional complexity)

Datum pg_kll_float_sketch_get_histogram(PG_FUNCTION_ARGS) {
  const bytea* bytes_in;
  void* sketchptr;
  int num_bins;

  // output array of bins
  Datum* result;
  ArrayType* arr_out;
  int16 elmlen_out;
  bool elmbyval_out;
  char elmalign_out;
  int arr_len_out;

  float* split_points;
  float min_value;
  float max_value;
  float delta;
  int i;

  bytes_in = PG_GETARG_BYTEA_P(0);
  sketchptr = kll_float_sketch_deserialize(VARDATA(bytes_in), VARSIZE(bytes_in) - VARHDRSZ);

  num_bins = PG_NARGS() > 1 ? PG_GETARG_INT32(1) : DEFAULT_NUM_BINS;
  if (num_bins < 2) {
    elog(ERROR, "at least two bins expected");
  }

  split_points = palloc(sizeof(float) * (num_bins - 1));
  min_value = kll_float_sketch_get_quantile(sketchptr, 0);
  max_value = kll_float_sketch_get_quantile(sketchptr, 1);
  delta = (max_value - min_value) / num_bins;
  for (i = 0; i < num_bins - 1; i++) {
    split_points[i] = min_value + delta * (i + 1);
  }
  result = (Datum*) kll_float_sketch_get_pmf_or_cdf(sketchptr, split_points, num_bins - 1, false, true);
  pfree(split_points);

  // construct output array
  arr_len_out = num_bins;
  get_typlenbyvalalign(FLOAT8OID, &elmlen_out, &elmbyval_out, &elmalign_out);
  arr_out = construct_array(result, arr_len_out, FLOAT8OID, elmlen_out, elmbyval_out, elmalign_out);

  kll_float_sketch_delete(sketchptr);

  PG_RETURN_ARRAYTYPE_P(arr_out);
}