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Collect writes without decoding
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lib/btree/writer.ex
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lib/btree/writer.ex
···
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end
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defp do_flush(%BTree{} = btree, page_index, page_checksum, page_sk, page_ek) do
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{page_type, pairs} =
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BTree.read_page(btree.page_store, page_index, page_checksum)
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|> Page.decode_page()
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%{
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page_store: page_store,
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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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page_data = BTree.read_page(page_store, page_index, page_checksum)
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prefix_size = opt_page_size - c_page_trailer_bytes()
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# See constant: c_page_trailer_bytes()
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<<
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_::binary-size(prefix_size),
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_count::integer-16,
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type_byte::integer-8,
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>> = page_data
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case type_byte do
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0x00 -> flush_inner(btree, page_data, page_sk, page_ek)
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0x01 -> do_flush_leaf(btree, page_data, page_sk, page_ek)
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end
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end
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defp flush_inner(%BTree{} = btree, page_data, page_sk, page_ek) do
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%{
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write_buffer: write_buffer,
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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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prefix_size = opt_page_size - c_page_trailer_bytes()
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# See constant: c_page_trailer_bytes()
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<<
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_::binary-size(prefix_size),
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pointer_count::integer-16,
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type_byte::integer-8,
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>> = page_data
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assert type_byte == 0x00
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key_count = pointer_count - 1
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slots_start = opt_page_size - (key_count * c_page_slot_entry_bytes())
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pointers_start = slots_start - (pointer_count * c_inner_pointer_bytes())
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writes = collect_inner_writes(btree, write_buffer, page_data, page_ek, slots_start, pointers_start, key_count, pointer_count, [], page_sk, 0)
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end
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defp collect_inner_writes(_btree, _write_buffer, _page_data, _page_ek, _slots_start, _pointers_start, _key_count, pointer_count, writes_acc, _start_key, i)
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when i == (pointer_count - 1) do
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Enum.reverse(writes_acc)
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end
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defp collect_inner_writes(btree, write_buffer, page_data, page_ek, slots_start, pointers_start, key_count, pointer_count, writes_acc, start_key, i) do
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assert i < pointer_count
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end_key = inner_end_key(page_data, page_ek, slots_start, key_count, i)
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case :ets.first(write_buffer) do
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key when is_binary(key) and key < end_key ->
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<<_::binary-size(pointers_start + (i * c_inner_pointer_bytes())), index::integer-64, checksum::binary-16, _::binary>> = page_data
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addresses = do_flush(btree, index, checksum, start_key, end_key)
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pairs =
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case page_type do
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:inner -> fill_inner(btree, pairs, page_sk, page_ek, [])
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:leaf -> fill_leaf(btree.write_buffer, page_ek, pairs)
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end
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writes_acc = [{i, addresses} | writes_acc]
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start_key = end_key
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i = i + 1
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collect_inner_writes(btree, write_buffer, page_data, page_ek, slots_start, pointers_start, key_count, pointer_count, writes_acc, start_key, i)
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_ ->
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start_key = end_key
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i = i + 1
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collect_inner_writes(btree, write_buffer, page_data, page_ek, slots_start, pointers_start, key_count, pointer_count, writes_acc, start_key, i)
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end
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end
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defp inner_end_key(page_data, page_ek, slots_start, key_count, i) do
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case i < key_count do
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true ->
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<<_::binary-size(slots_start + (i * c_page_slot_entry_bytes())), key_offset::integer-16, _::binary>> = page_data
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<<_::binary-size(key_offset), key_size::integer-16, key::binary-size(key_size), _::binary>> = page_data
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key
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false -> page_ek
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end
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end
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defp do_flush_leaf(btree, page_data, page_sk, page_ek) do
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{page_type, pairs} = Page.decode_page(page_data)
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assert page_type == :leaf
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pairs = fill_leaf(btree.write_buffer, page_ek, pairs)
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new_encoded_pages = Page.encode_page_from_pairs(page_type, btree.opts.page_size, pairs, page_ek)
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assert elem(List.last(new_encoded_pages), 0) == page_ek
···
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slots_data = encode_slots(offsets, "")
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type_byte = 0x00
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# See constant: c_page_trailer_bytes()
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page = <<
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keys_data::binary,
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0::integer-unit(8)-size(pad_bytes),