[C++][Parquet] Make MemoryPool settable on ReaderProperties

[pitrou]

Describe the enhancement requested

In arrow/dataset/file_parquet.cc, we have to set all Parquet ReaderProperties explicitly one by one from the source configuration, only because we cannot use the ReaderProperties copy constructor and afterwards set the MemoryPool to a different value:

arrow/cpp/src/arrow/dataset/file_parquet.cc

Lines 71 to 78 in 05c1a4b

	// Can't mutate pool after construction
	parquet::ReaderProperties properties(pool);
	if (parquet_scan_options->reader_properties->is_buffered_stream_enabled()) {
	properties.enable_buffered_stream();
	} else {
	properties.disable_buffered_stream();
	}
	properties.set_buffer_size(parquet_scan_options->reader_properties->buffer_size());

We should make MemoryPool settable on ReaderProperties, and then simplify the dataset code to use the ReaderProperties copy constructor.

Component(s)

C++, Parquet

[Diveyam-Mishra]

Take