Gang Wu

> @tustvold @crepererum @westonpace I would especially like to get your opions on this, as you were proponents of total order for simplicity. Does this PR still cover what you...

I guess `BIT_PACKED` was the only encoding for definition and repetition levels at the time implementing this so it was used as the default value. It seems better to return...

I think the encoding value depends on the writer implementation. For pyarrow (which uses parquet-cpp internally) it makes sense to write `RLE`.

I mean a writer implementation which still encodes levels using deprecated `BIT_PACKED` should write `BIT_PACKED` in the header. Otherwise, all new writer implementations should use `RLE` and thus write `RLE`...