this repo has no description
Add writer for new inner page format
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lib/btree/utils.ex
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lib/btree/utils.ex
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lib/btree/writer.ex
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lib/btree/writer.ex
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alias Hobbes.BTree.{FreeList, Page}
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import ExUnit.Assertions, only: [assert: 1]
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import Hobbes.BTree.Utils
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@keyspace_start_key ""
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@keyspace_end_key "\xFF\xFF\xFF\xFF"
···
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_ -> pairs_acc
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end
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end
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defp write_inner(%BTree{} = btree, end_key, pairs) do
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%{
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opts: %{
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page_size: opt_page_size,
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},
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} = btree
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{keys_data, pointers_data, offsets, count} = do_write_inner(pairs, "", "", [], 0)
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maybe_split_inner(opt_page_size, end_key, keys_data, pointers_data, offsets, count)
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end
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# Have (p = pointer, k = key)
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# p - k - p - k - p - k - p
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#
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# Want
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# k
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# / \
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# p - k - p p - k - p
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#
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# 0 1 2
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# k k k
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# p p p p
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defp maybe_split_inner(opt_page_size, end_key, keys_data, pointers_data, offsets, pointer_count) do
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key_count = pointer_count - 1
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data_size = byte_size(keys_data) + byte_size(pointers_data) + (key_count * c_page_slot_entry_bytes()) + c_page_trailer_bytes()
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case data_size <= opt_page_size do
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true ->
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pad_bytes = opt_page_size - data_size
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assert pad_bytes >= 0
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slots_data = encode_slots(offsets, "")
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type_byte = 0x00
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page = <<
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keys_data::binary,
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0::integer-unit(8)-size(pad_bytes),
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pointers_data::binary,
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slots_data::binary,
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pointer_count::integer-16,
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type_byte::integer-8,
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>>
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[{end_key, page}]
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false ->
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assert key_count >= 3
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midpoint_i = div(key_count, 2)
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{offsets1, offsets2} = Enum.split(offsets, midpoint_i)
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[offset_mid | offsets2] = offsets2
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assert offsets2 != []
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<<
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keys_data1::binary-size(offset_mid),
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mid_key_size::integer-16,
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mid_key::binary-size(mid_key_size),
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keys_data2::binary,
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>> = keys_data
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pointer_count1 = midpoint_i + 1
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pointer_count2 = pointer_count - pointer_count1
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<<
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pointers_data1::binary-size(pointer_count1 * c_inner_pointer_bytes()),
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pointers_data2::binary,
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>> = pointers_data
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end_key1 = mid_key
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end_key2 = end_key
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pages1 = maybe_split_inner(opt_page_size, end_key1, keys_data1, pointers_data1, offsets1, pointer_count1)
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pages2 = maybe_split_inner(opt_page_size, end_key2, keys_data2, pointers_data2, offsets2, pointer_count2)
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pages1 ++ pages2
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end
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end
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defp do_write_inner([{_end_key, pointer}], keys_acc, pointers_acc, offsets_acc, count_acc) do
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#assert end_key == nil
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assert byte_size(pointer) == 24
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pointers_acc = <<
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pointers_acc::binary,
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pointer::binary,
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>>
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count_acc = count_acc + 1
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{keys_acc, pointers_acc, Enum.reverse(offsets_acc), count_acc}
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end
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defp do_write_inner([{key, pointer} | pairs_rest], keys_acc, pointers_acc, offsets_acc, count_acc) do
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offset = byte_size(keys_acc)
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key_size = byte_size(key)
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keys_acc = <<
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keys_acc::binary,
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key_size::integer-16,
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key::binary,
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>>
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assert byte_size(pointer) == 24
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pointers_acc = <<
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pointers_acc::binary,
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pointer::binary,
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>>
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offsets_acc = [offset | offsets_acc]
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count_acc = count_acc + 1
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do_write_inner(pairs_rest, keys_acc, pointers_acc, offsets_acc, count_acc)
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end
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defp encode_slots([], slots_acc), do: slots_acc
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defp encode_slots([offset | offsets_rest], slots_acc) do
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assert offset < (2 ** 16)
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# See constant: c_page_slot_entry_bytes()
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slots_acc = <<
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slots_acc::binary,
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offset::integer-16,
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>>
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encode_slots(offsets_rest, slots_acc)
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end
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end