C++ ARROW_DEPRECATED Use MemoryPool-less variant

[Weber, Eugene]

Hi,


When I compile example.cc under cpp/examples/minimal_build I get a depreciation 
warning on:


      arrow::csv::TableReader::Make(arrow::default_memory_pool(),
                                    arrow::io::default_io_context(),
                                    input_file,
                                    arrow::csv::ReadOptions::Defaults(),
                                    arrow::csv::ParseOptions::Defaults(),
                                    arrow::csv::ConvertOptions::Defaults()));


The deprecation code in reader.h is:


  ARROW_DEPRECATED("Use MemoryPool-less variant (the IOContext holds a pool 
already)")
  static Result<std::shared_ptr<TableReader>> Make(
      MemoryPool* pool, io::IOContext io_context, 
std::shared_ptr<io::InputStream> input,
      const ReadOptions&, const ParseOptions&, const ConvertOptions&);


I've read the documentation on MemoryPool, but I'm still not fully 
understanding the relationship between TableReader and MemoryPool, or how 
exactly to correct the example code. I understand that the CVS table is read 
into a table structure in memory allocated from the memory pool. I'm not 
understanding the meaning of "Use MemoryPool-less variant (the IOContext holds 
a pool already)".


Thanks in advance for the clarification.


Gene