pub fn read_columns_many<'a, R: Read + Seek>(
reader: &mut R,
row_group: &RowGroupMetaData,
fields: Vec<Field>,
chunk_size: Option<usize>
) -> Result<Vec<ArrayIter<'a>>>Expand description
Returns a vector of iterators of Array (ArrayIter) corresponding to the top
level parquet fields whose name matches fields’s names.
Implementation
This operation is IO-bounded O(C) where C is the number of columns in the row group -
it reads all the columns to memory from the row group associated to the requested fields.
This operation is single-threaded. For readers with stronger invariants
(e.g. implement Clone) you can use read_columns to read multiple columns at once
and convert them to ArrayIter via to_deserializer.