Function ExecIndexEvalArrayKeys

src/backend/executor/nodeIndexscan.c:663–733

* ExecIndexEvalArrayKeys * Evaluate any array key values, and set up to iterate through arrays. * * Returns true if there are array elements to consider; false means there * is at least one null or empty array, so no match is possible. On true * result, the scankeys are initialized with the first elements of the arrays. */

 * result, the scankeys are initialized with the first elements of the arrays.
 */
bool
ExecIndexEvalArrayKeys(ExprContext *econtext,
					   IndexArrayKeyInfo *arrayKeys, int numArrayKeys)
{
	bool		result = true;
	int			j;
	MemoryContext oldContext;

	/* We want to keep the arrays in per-tuple memory */
	oldContext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);

	for (j = 0; j < numArrayKeys; j++)
	{
		ScanKey		scan_key = arrayKeys[j].scan_key;
		ExprState  *array_expr = arrayKeys[j].array_expr;
		Datum		arraydatum;
		bool		isNull;
		ArrayType  *arrayval;
		int16		elmlen;
		bool		elmbyval;
		char		elmalign;
		int			num_elems;
		Datum	   *elem_values;
		bool	   *elem_nulls;

		/*
		 * Compute and deconstruct the array expression. (Notes in
		 * ExecIndexEvalRuntimeKeys() apply here too.)
		 */
		arraydatum = ExecEvalExpr(array_expr,
								  econtext,
								  &isNull);
		if (isNull)
		{
			result = false;
			break;				/* no point in evaluating more */
		}
		arrayval = DatumGetArrayTypeP(arraydatum);
		/* We could cache this data, but not clear it's worth it */
		get_typlenbyvalalign(ARR_ELEMTYPE(arrayval),
							 &elmlen, &elmbyval, &elmalign);
		deconstruct_array(arrayval,
						  ARR_ELEMTYPE(arrayval),
						  elmlen, elmbyval, elmalign,
						  &elem_values, &elem_nulls, &num_elems);
		if (num_elems <= 0)
		{
			result = false;
			break;				/* no point in evaluating more */
		}

		/*
		 * Note: we expect the previous array data, if any, to be
		 * automatically freed by resetting the per-tuple context; hence no
		 * pfree's here.
		 */
		arrayKeys[j].elem_values = elem_values;
		arrayKeys[j].elem_nulls = elem_nulls;