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Range tombstones are kept in memory (cache/memtable) in range_tombstone_list. It keeps them deoverlapped, so applying a range tombstone which covers many range tombstones will erase existing range tombstones from the list. This operation needs to be exception-safe, so range_tombstone_list maintains an undo log. This undo log will receive a record for each range tombstone which is removed. For exception safety reasons, before pushing an undo log entry, we reserve space in the log by calling std::vector::reserve(size() + 1). This is O(N) where N is the number of undo log entries. Therefore, the whole application is O(N^2). This can cause reactor stalls and availability issues when replicas apply such deletions. This patch avoids the problem by reserving exponentially increasing amount of space. Also, to avoid large allocations, switches the container to chunked_vector. Fixes #11211 Closes #11215