Struct GenericColumnReader

pub struct GenericColumnReader<R, D, V> { /* private fields */ }

Reads data for a given column chunk, using the provided decoders:

• R: ColumnLevelDecoder used to decode repetition levels
• D: ColumnLevelDecoder used to decode definition levels
• V: ColumnValueDecoder used to decode value data

Implementations

impl<V> GenericColumnReader<RepetitionLevelDecoderImpl, DefinitionLevelDecoderImpl, V>

where V: ColumnValueDecoder,

pub fn new(descr: ColumnDescPtr, page_reader: Box<dyn PageReader>) -> Self

Creates new column reader based on column descriptor and page reader.

impl<R, D, V> GenericColumnReader<R, D, V>

where R: RepetitionLevelDecoder, D: DefinitionLevelDecoder, V: ColumnValueDecoder,

pub fn read_records( &mut self, max_records: usize, def_levels: Option<&mut D::Buffer>, rep_levels: Option<&mut R::Buffer>, values: &mut V::Buffer, ) -> Result<(usize, usize, usize)>

Read up to max_records whole records, returning the number of complete records, non-null values and levels decoded. All levels for a given record will be read, i.e. the next repetition level, if any, will be 0

If the max definition level is 0, def_levels will be ignored and the number of records, non-null values and levels decoded will all be equal, otherwise def_levels will be populated with the number of levels read, with an error returned if it is None.

If the max repetition level is 0, rep_levels will be ignored and the number of records and levels decoded will both be equal, otherwise rep_levels will be populated with the number of levels read, with an error returned if it is None.

values will be contiguously populated with the non-null values. Note that if the column is not required, this may be less than either max_records or the number of levels read

pub fn skip_records(&mut self, num_records: usize) -> Result<usize>

Skips over num_records records, where records are delimited by repetition levels of 0

Returns

Returns the number of records skipped