Administration - Installation - Core: Missing Index on tax_tree.child?

We were running an E-Assessment with random questions from a big question pool and taxonomies for the first time and observed extremely degraded performance on our ILIAS system.
It turned out that adding an Index to tax_tree.child substantially improved performance. On an idle system with about 80 questions, invoking the test took about 5s. With 70 participants, ILIAS was unresponsive for about 5 to 10 minutes.
Benchmarking the issue, we found the following query:
SELECT
 s.child
FROM
 tax_tree s, tax_tree t
WHERE
 t.child = 8385
AND
 s.lft > t.lft
AND
 s.rgt < t.rgt
AND
 s.tax_tree_id = 18710;

The query execution plan looked like this:
id    select_type    table    type    possible_keys    key            key_len    ref        rows    Extra
1    SIMPLE        s        ref        PRIMARY            PRIMARY        4        const    59    
1    SIMPLE        t        ALL        NULL            NULL        NULL    NULL    2571    Using where

After running
CREATE INDEX IF NOT EXISTS IDX_CHILD ON tax_tree (child) USING HASH;

the query execution plan was:
id    select_type    table    type    possible_keys    key            key_len    ref        rows    Extra
1    SIMPLE        t        ref        IDX_CHILD        IDX_CHILD    4        const    1    
1    SIMPLE        s        ref        PRIMARY            PRIMARY        4        const    59    Using where

and benchmark resulted in a total query time of 0.55s

Do you think it's worth submitting a pull request?

Cheers, Felix