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Split root recursively as needed
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lib/btree/writer.ex
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lib/btree/writer.ex
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alias Hobbes.BTree
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alias Hobbes.BTree.{FreeList, Page}
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import ExUnit.Assertions, only: [assert: 1]
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@keyspace_start_key ""
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@keyspace_end_key "\xFF\xFF\xFF\xFF"
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@spec apply_batch(BTree.t, list) :: :ok
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def apply_batch(%BTree{} = btree, mutations) do
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%{
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[{:root_address, {root_index, root_checksum}}] = :ets.lookup(root_store, :root_address)
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[{_, <<new_ri::integer-64, new_rch::binary-16>>}] = do_flush(btree, root_index, root_checksum, "", "\xFF\xFF\xFF\xFF")
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{new_root_index, new_root_checksum} = flush_tree(btree, root_index, root_checksum)
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:ets.insert(root_store, {:root_address, {new_ri, new_rch}})
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:ets.insert(root_store, {:root_address, {new_root_index, new_root_checksum}})
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:ok
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end
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···
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{:clear, k} -> :ets.insert(write_buffer, {k, :tombstone})
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end
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do_write_buffer(mutations_rest, write_buffer)
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end
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defp flush_tree(%BTree{} = btree, root_index, root_checksum) do
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root_addresses = do_flush(btree, root_index, root_checksum, @keyspace_start_key, @keyspace_end_key)
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maybe_split_root(btree, root_addresses)
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end
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defp maybe_split_root(%BTree{} = btree, root_addresses) do
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case root_addresses do
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[{_ek, address}] ->
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<<root_index::integer-64, root_checksum::binary-16>> = address
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{root_index, root_checksum}
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pairs ->
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assert root_addresses != []
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new_root_data = Page.encode_page_from_pairs(:leaf, btree.opts.page_size, pairs, @keyspace_end_key)
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new_indices = FreeList.reserve_pages(btree.free_list, length(new_root_data))
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new_root_addresses =
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Enum.zip(new_root_data, new_indices)
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|> Enum.map(fn {{ek, data}, index} ->
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:ok = BTree.write_page(btree.page_store, index, data)
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checksum = BTree.checksum(data)
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{ek, <<index::integer-64, checksum::binary-16>>}
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end)
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# We check if the root needs to be split again
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# TODO: ensure this is fuzzed as it will be rare in practice
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maybe_split_root(btree, new_root_addresses)
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end
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end
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defp do_flush(%BTree{} = btree, page_index, page_checksum, page_sk, page_ek) do