Function exec_stmt_foreach_a

src/pl/plpgsql/src/pl_exec.c:2947–3094

---------- * exec_stmt_foreach_a Loop over elements or slices of an array * * When looping over elements, the loop variable is the same type that the * array stores (eg: integer), when looping through slices, the loop variable * is an array of size and dimensions to match the size of the slice. * ---------- */

 * ----------
 */
static int
exec_stmt_foreach_a(PLpgSQL_execstate *estate, PLpgSQL_stmt_foreach_a *stmt)
{
	ArrayType  *arr;
	Oid			arrtype;
	int32		arrtypmod;
	PLpgSQL_datum *loop_var;
	Oid			loop_var_elem_type;
	bool		found = false;
	int			rc = PLPGSQL_RC_OK;
	MemoryContext stmt_mcontext;
	MemoryContext oldcontext;
	ArrayIterator array_iterator;
	Oid			iterator_result_type;
	int32		iterator_result_typmod;
	Datum		value;
	bool		isnull;

	/* get the value of the array expression */
	value = exec_eval_expr(estate, stmt->expr, &isnull, &arrtype, &arrtypmod);
	if (isnull)
		ereport(ERROR,
				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
				 errmsg("FOREACH expression must not be null")));

	/*
	 * Do as much as possible of the code below in stmt_mcontext, to avoid any
	 * leaks from called subroutines.  We need a private stmt_mcontext since
	 * we'll be calling arbitrary statement code.
	 */
	stmt_mcontext = get_stmt_mcontext(estate);
	push_stmt_mcontext(estate);
	oldcontext = MemoryContextSwitchTo(stmt_mcontext);

	/* check the type of the expression - must be an array */
	if (!OidIsValid(get_element_type(arrtype)))
		ereport(ERROR,
				(errcode(ERRCODE_DATATYPE_MISMATCH),
				 errmsg("FOREACH expression must yield an array, not type %s",
						format_type_be(arrtype))));

	/*
	 * We must copy the array into stmt_mcontext, else it will disappear in
	 * exec_eval_cleanup.  This is annoying, but cleanup will certainly happen
	 * while running the loop body, so we have little choice.
	 */
	arr = DatumGetArrayTypePCopy(value);

	/* Clean up any leftover temporary memory */
	exec_eval_cleanup(estate);

	/* Slice dimension must be less than or equal to array dimension */
	if (stmt->slice < 0 || stmt->slice > ARR_NDIM(arr))
		ereport(ERROR,
				(errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
				 errmsg("slice dimension (%d) is out of the valid range 0..%d",
						stmt->slice, ARR_NDIM(arr))));