Function ExecIndexAdvanceArrayKeys

src/backend/executor/nodeIndexscan.c:742–780

* ExecIndexAdvanceArrayKeys * Advance to the next set of array key values, if any. * * Returns true if there is another set of values to consider, false if not. * On true result, the scankeys are initialized with the next set of values. */

 * On true result, the scankeys are initialized with the next set of values.
 */
bool
ExecIndexAdvanceArrayKeys(IndexArrayKeyInfo *arrayKeys, int numArrayKeys)
{
	bool		found = false;
	int			j;

	/*
	 * Note we advance the rightmost array key most quickly, since it will
	 * correspond to the lowest-order index column among the available
	 * qualifications.  This is hypothesized to result in better locality of
	 * access in the index.
	 */
	for (j = numArrayKeys - 1; j >= 0; j--)
	{
		ScanKey		scan_key = arrayKeys[j].scan_key;
		int			next_elem = arrayKeys[j].next_elem;
		int			num_elems = arrayKeys[j].num_elems;
		Datum	   *elem_values = arrayKeys[j].elem_values;
		bool	   *elem_nulls = arrayKeys[j].elem_nulls;

		if (next_elem >= num_elems)
		{
			next_elem = 0;
			found = false;		/* need to advance next array key */
		}
		else
			found = true;
		scan_key->sk_argument = elem_values[next_elem];
		if (elem_nulls[next_elem])
			scan_key->sk_flags |= SK_ISNULL;
		else
			scan_key->sk_flags &= ~SK_ISNULL;
		arrayKeys[j].next_elem = next_elem + 1;
		if (found)
			break;
	}

	return found;
}


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