“condition_pushdown_for_derived” optimization not used when using INSERT INTO

“condition_pushdown_for_derived” optimization correctly use index withing a simple SELECT query, but don't use it if the result records are inserted into an existing table.

Steps to reproduce:

CREATE TABLE `tbl` (
`a` INT(11) NULL DEFAULT NULL,
`b` INT(11) NULL DEFAULT NULL,
INDEX `a` (`a`)
);

INSERT INTO `tbl` (`a`, `b`) VALUES
(1, 1),
(1, 2),
(2, 1),
(2, 2);

CREATE TABLE `tbl2` (
`a` INT(11) NULL DEFAULT NULL,
`b` INT(11) NULL DEFAULT NULL
);

Simple select query:

EXPLAIN
SELECT * FROM
(SELECT a,b FROM tbl GROUP BY a) t
WHERE a=1;

Adding INSERT INTO index is no more used:

EXPLAIN
INSERT INTO tbl2
SELECT * FROM
(SELECT a,b FROM tbl GROUP BY a) t
WHERE a=1;

For comparison, i tried a query without GROUP BY (in this case the optimization involved is derived_merge), and the optimization is maintained when using INSERT INTO

EXPLAIN
SELECT * FROM
(SELECT * FROM tbl) t
WHERE a=1;

EXPLAIN
INSERT INTO tbl2
SELECT * FROM
(SELECT * FROM tbl) t
WHERE a=1;