Function buildHistogramEntryForStats

src/backend/commands/analyzeutils.c:651–682

* Preparing the output array of histogram bounds, removing any duplicates * Input: * ldatum - list of pointers to the aggregated bounds, may contain duplicates * typInfo - type information * Output: * an array containing the aggregated histogram bounds */

 *  an array containing the aggregated histogram bounds
 */
static Datum *
buildHistogramEntryForStats(List *ldatum, TypInfo *typInfo, int *num_hist)
{
	Assert(ldatum);
	Assert(typInfo);

	Datum	   *histArray = (Datum *) palloc(sizeof(Datum) * list_length(ldatum));

	ListCell   *lc;
	Datum	   *prevDatum = (Datum *) linitial(ldatum);
	int			idx = 0;

	*num_hist = 0;

	foreach_with_count(lc, ldatum, idx)
	{
		Datum	   *pdatum = (Datum *) lfirst(lc);

		/* remove duplicate datum in the list, starting from the second datum */
		if (OidFunctionCall2Coll(typInfo->eqFuncOp, typInfo->collid,
								 *pdatum, *prevDatum) && idx > 0)
		{
			continue;
		}

		histArray[*num_hist] = *pdatum;
		*num_hist = *num_hist + 1;
		*prevDatum = *pdatum;
	}

	return histArray;
}


/*