parquet::column::reader::decoder

Trait ColumnValueDecoder

Source 
pub trait ColumnValueDecoder {
    type Buffer;

    // Required methods
    fn new(col: &ColumnDescPtr) -> Self;
    fn set_dict(
        &mut self,
        buf: Bytes,
        num_values: u32,
        encoding: Encoding,
        is_sorted: bool,
    ) -> Result<()>;
    fn set_data(
        &mut self,
        encoding: Encoding,
        data: Bytes,
        num_levels: usize,
        num_values: Option<usize>,
    ) -> Result<()>;
    fn read(
        &mut self,
        out: &mut Self::Buffer,
        num_values: usize,
    ) -> Result<usize>;
    fn skip_values(&mut self, num_values: usize) -> Result<usize>;
}
Expand description

Decodes value data

Required Associated Types§

Source

type Buffer

Required Methods§

Source

fn new(col: &ColumnDescPtr) -> Self

Create a new ColumnValueDecoder

Source

fn set_dict( &mut self, buf: Bytes, num_values: u32, encoding: Encoding, is_sorted: bool, ) -> Result<()>

Set the current dictionary page

Source

fn set_data( &mut self, encoding: Encoding, data: Bytes, num_levels: usize, num_values: Option<usize>, ) -> Result<()>

Set the current data page

  • encoding - the encoding of the page
  • data - a point to the page’s uncompressed value data
  • num_levels - the number of levels contained within the page, i.e. values including nulls
  • num_values - the number of non-null values contained within the page (V2 page only)

Note: data encoded with Encoding::RLE may not know its exact length, as the final run may be zero-padded. As such if num_values is not provided (i.e. None), subsequent calls to ColumnValueDecoder::read may yield more values than non-null definition levels within the page

Source

fn read(&mut self, out: &mut Self::Buffer, num_values: usize) -> Result<usize>

Read up to num_values values into out

§Panics

Implementations may panic if range overlaps with already written data

Source

fn skip_values(&mut self, num_values: usize) -> Result<usize>

Skips over num_values values

Returns the number of values skipped

Dyn Compatibility§

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors§