Previously, with the `index_experimental` feature enabled, the query in
the added test would enter an infinite loop. This happened because
`label_grouping_agg_step` pointed to a constant argument that was moved
to the end of the program. As a result, the aggregation loop would jump
to the constant, then return to the start of the main loop, rewind the
index, and re-enter the aggregation loop—causing it to repeat
indefinitely.
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