CharlesO

CharlesO OP 

000007775B4C4900000136490000000049FFFFFFFF4C49000000674900000000 4900000005 # row count
	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
3B3B5D

JQL is not so tricky. You can see the core repeating pattern above:

data-body header row-count
row-header - row-length - row data - row terminator
...
...
data-body terminator
0
Post #12
CharlesO

CharlesO OP

Thanks for this. This is recursion 101, i know but i felt the size of each row was small enough to accumulate the parsed items left - right, as they occur in the data packet. The place i’ve really goofed is here:

 defp _r(
         <<"LI", 0x136::32, "I", 0::32, "I", _::32, "LI", 0x67::32, "I", 0::32, "I", n::32, b::bits>>,
         []
       ) do
    v =
      for <<l::32, s::bytes-size(l), _::bits>> <-
            :binary.split(b, @_00jb, [:global]),
          do: _split(s)

    {:data, n, v}
  end

on this line:

 v =
      for <<l::32, s::bytes-size(l), _::bits>> <-
            :binary.split(b, @_00jb, [:global]),
          do: _split(s)

i’m practically saying split the 850mb blob of data (2.5m+ rows), and build a list out of it … all at once in memory

When i run same routine for 5, 100 or even 100,000 rows it complete without issues.

I need a way to process and discard each row and not accumulate to lists like i’m doing, like you guys have rightly pointed out, more so NOT using ++ to accumulate

0
Post #13
benwilson512

benwilson512

Author of Craft GraphQL APIs in Elixir with Absinthe

You can do this, you just have to write it body recursive instead of tail recursive.

1
Post #14
CharlesO

CharlesO OP

Found a really simple way to solve this. Just read the data-header, then parse row by row:

  def read(src, cnt \\ nil) do
    {:ok, fid} = :file.open("_cache/#{src}", [:raw, :read, :binary])
    {:h, start, n} = _p(fid, :h)

    cnt = cnt || n

    Logger.debug("Reading: #{cnt} of #{n} rows")

    Process.put(:start_pos, start)

    for i <- 1..cnt do
      {:r, start, row} = _p(fid, Process.get(:start_pos), :r)
      Process.put(:start_pos, start)
      Logger.debug(inspect({i, row}, @format))
    end

    :file.close(fid)
  end

  # READER
  defp _p(fid, :h) do
    # 000007775B4C4900000136490000000049FFFFFFFF4C490000006749000000004900000005
    {:ok, <<n::32>>} = :file.pread(fid, 33, 4)
    {:h, 37, n}
  end

  defp _p(fid, start, :r) do
    # 490000000049000000006A62 00000165 3136333737303....
    {:ok, <<l::32>>} = :file.pread(fid, start + 12, 4)
    {:ok, b} = :file.pread(fid, start + 16, l)

    {:r, start + l + 18, _split(b)}
  end

  defp _split(v) do
    b = for(<<c <- v>>, c in 32..126 || c in [252, 253, 254], into: "", do: <<c>>)
    b = :binary.replace(b, <<253>>, ";", [:global])
    b = :binary.replace(b, <<252>>, "^", [:global])
    :binary.split(b, <<254>>, [:global])
  end
3
Post #15
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