elasticsearch/docs/reference/migration/migrate_8_0/indices.asciidoc

[float]
[[breaking_80_indices_changes]]
=== Force Merge API changes

Previously, the Force Merge API allowed the parameters `only_expunge_deletes`
and `max_num_segments` to be set to a non default value at the same time. But
the `max_num_segments` was silently ignored when `only_expunge_deletes` is set
to `true`, leaving the false impression that it has been applied.

The Force Merge API now rejects requests that have a `max_num_segments` greater
than or equal to 0 when the `only_expunge_deletes` is set to true.