Function decode_block

nodedb-columnar/src/reader/block_decode.rs:149–297

Decode a single block and append results to the DecodedColumn.

(
    result: &mut DecodedColumn,
    block_data: &[u8],
    kind: &ColumnKind,
    codec: ResolvedColumnCodec,
    row_count: usize,
    dictionary: Option<&[String]>,
)

/// Decode a single block and append results to the DecodedColumn.
pub(super) fn decode_block(
    result: &mut DecodedColumn,
    block_data: &[u8],
    kind: &ColumnKind,
    codec: ResolvedColumnCodec,
    row_count: usize,
    dictionary: Option<&[String]>,
) -> Result<(), ColumnarError> {
    let bitmap_size = row_count.div_ceil(8);

    if block_data.len() < bitmap_size {
        return Err(ColumnarError::TruncatedSegment {
            expected: bitmap_size,
            got: block_data.len(),
        });
    }

    let bitmap = &block_data[..bitmap_size];
    let payload = &block_data[bitmap_size..];

    // Extract validity from bitmap.
    let valid: Vec<bool> = (0..row_count)
        .map(|i| bitmap[i / 8] & (1 << (i % 8)) != 0)
        .collect();

    match kind {
        ColumnKind::Int64 => {
            let DecodedColumn::Int64 { values, valid: v } = result else {
                append_null_fill(result, row_count);
                return Ok(());
            };
            let decoded = nodedb_codec::decode_i64_pipeline(payload, codec.into_column_codec())?;
            values.extend_from_slice(&decoded[..row_count.min(decoded.len())]);
            while values.len() < v.len() + row_count {
                values.push(0);
            }
            v.extend_from_slice(&valid);
        }
        ColumnKind::Float64 => {
            let DecodedColumn::Float64 { values, valid: v } = result else {
                append_null_fill(result, row_count);
                return Ok(());
            };
            let decoded = nodedb_codec::decode_f64_pipeline(payload, codec.into_column_codec())?;
            values.extend_from_slice(&decoded[..row_count.min(decoded.len())]);
            while values.len() < v.len() + row_count {
                values.push(0.0);
            }
            v.extend_from_slice(&valid);
        }
        ColumnKind::VarLen => {
            let DecodedColumn::Binary {
                data,
                offsets,
                valid: v,
            } = result
            else {
                append_null_fill(result, row_count);