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, 4) with mask 1000. The next chunk skips to row 11 and decodes [11, 12) with mask 1. The loaded ranges are decode boundaries, not output batch boundaries: ParquetRecordBatchReader accumulates both chunks and applies the combined mask 10001 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.

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.