Remove unused index space. For the memtx storage engine this method does nothing;
index_object:compact()is only for the vinyl storage engine. For example, with vinyl, if a tuple is deleted, the space is not immediately reclaimed. There is a scheduler for reclaiming space automatically based on factors such as lsm shape and amplification as discussed in the section Storing data with vinyl, so calling
index_object:compact()manually is not always necessary.
Return: nil (Tarantool returns without waiting for compaction to complete)