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cf352e7c14
needs_cleanup() returns true if a sstable needs cleanup. Turns out it's very slow because it iterates through all the local ranges for all sstables in the set, making its complexity: O(num_sstables * local_ranges) We can optimize it by taking into account that abstract_replication_strategy documents that get_ranges() will return a list of ranges that is sorted and non-overlapping. Compaction for cleanup already takes advantage of that when checking if a given partition can be actually purged. So needs_cleanup() can be optimized into O(num_sstables * log(local_ranges)). With num_sstables=1000, RF=3, then local_ranges=256(num_tokens)*3, it means the max # of checks performed will go from 768000 to ~9584. Fixes #6730. Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com> Message-Id: <20200629171355.45118-2-raphaelsc@scylladb.com>