Function detect_codec

nodedb-codec/src/detect.rs:30–45

Detect the optimal codec for a column based on its type and data. When `codec` is not `Auto`, returns it unchanged. When `Auto`, analyzes the column type hint to select the best codec. For data-aware selection (ALP encodability, monotonicity detection), use `detect_f64_codec()` or `detect_i64_codec()` with actual values.

(codec: ColumnCodec, type_hint: ColumnTypeHint)

/// data-aware selection (ALP encodability, monotonicity detection),
/// use `detect_f64_codec()` or `detect_i64_codec()` with actual values.
pub fn detect_codec(codec: ColumnCodec, type_hint: ColumnTypeHint) -> ColumnCodec {
    if codec != ColumnCodec::Auto {
        return codec;
    }

    // Default selections (data-unaware). The segment writer calls
    // data-aware variants (detect_f64_codec, detect_i64_codec) when
    // it has actual values.
    match type_hint {
        ColumnTypeHint::Timestamp => ColumnCodec::DeltaFastLanesLz4,
        ColumnTypeHint::Float64 => ColumnCodec::AlpFastLanesLz4,
        ColumnTypeHint::Int64 => ColumnCodec::DeltaFastLanesLz4,
        ColumnTypeHint::Symbol => ColumnCodec::FastLanesLz4,
        ColumnTypeHint::String => ColumnCodec::FsstLz4,
    }
}

/// Detect the optimal codec for an i64 column by analyzing the data.
///