Struct MaskCursor 

pub struct MaskCursor {
    mask: BooleanBuffer,
    position: usize,
    loaded_row_ranges: Option<Arc<LoadedRowRanges>>,
}

Cursor for iterating a mask-backed RowSelection

This is best for dense selections where there are many small skips or selections. For example, selecting every other row.

When page pruning produces sparse column data, loaded_row_ranges limits each decoded chunk to rows whose pages are loaded for every projected leaf. For example, two projected columns can have different page boundaries:

Row ranges:       [0, 4) [4, 6) [6, 8) [8, 10) [10, 12)
Selection mask:   1000   00     00     00      01
Column A pages:   loaded | missing [4, 8) | loaded [8, 12)
Column B pages:   loaded [0, 6) | missing [6, 10) | loaded
LoadedRowRanges:  [0, 4)                         [10, 12)

The first chunk decodes [0, 1) with mask 1. The next chunk skips to row 11 and decodes [11, 12) with mask 1. When loaded ranges are present, every returned chunk ends at a selected row and never includes trailing unselected rows. ParquetRecordBatchReader still accumulates both chunks and applies the combined mask 11 once.

Fields

mask: BooleanBuffer

position: usize

Current absolute offset into the selection

loaded_row_ranges: Option<Arc<LoadedRowRanges>>

Row ranges whose backing pages are loaded for every projected column.

Implementations

impl MaskCursor

pub fn is_empty(&self) -> bool

Returns true when no further rows remain

pub fn next_mask_chunk(&mut self, batch_size: usize) -> Option<MaskChunk>

Advance through the mask representation, producing the next chunk summary

fn next_mask_chunk_non_empty(&mut self, batch_size: usize) -> MaskChunk

Produces the next chunk for a non-empty, trailing-skip-free mask.

pub(crate) fn next_chunk( &mut self, batch_size: usize, ) -> Result<MaskChunk, ParquetError>

Returns the next non-empty mask chunk without crossing an unloaded row range. When loaded ranges are present, every returned chunk ends immediately after a selected row and therefore never contains trailing unselected rows. Those rows remain for the next call’s initial skip.

The ReadPlan removes trailing skips before constructing this cursor. Callers therefore only invoke this method for a non-empty mask that has another selected row.

pub fn mask_values_for( &self, chunk: &MaskChunk, ) -> Result<BooleanArray, ParquetError>

Materialise the boolean values for a mask-backed chunk

Trait Implementations

impl Debug for MaskCursor

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.