legacy.rs

// SPDX-License-Identifier: Apache-2.0
// SPDX-FileCopyrightText: Copyright the Vortex contributors

//! Compatibility helpers for stats still stored under the legacy [`Stat`] enum.

use crate::aggregate_fn::AggregateFnRef;
use crate::aggregate_fn::fns::nan_count::NanCount;
use crate::aggregate_fn::fns::sum::Sum;
use crate::aggregate_fn::fns::uncompressed_size_in_bytes::UncompressedSizeInBytes;
use crate::expr::stats::Stat;

/// Maps an aggregate function to its legacy [`Stat`] slot, if one exists.
///
/// Used while we still cache some aggregates under the legacy [`Stat`] enum rather than keyed
/// directly by aggregate function. New aggregates (e.g. `min_max`, `is_constant`, `is_sorted`,
/// `count`) intentionally have no mapping and return `None`; callers will see the `trace!`
/// below when they ask for an aggregate that isn't backed by a legacy slot.
pub(crate) fn legacy_stat_for_aggregate(aggregate_fn: &AggregateFnRef) -> Option<Stat> {
    if aggregate_fn.is::<Sum>() {
        return Some(Stat::Sum);
    }
    if aggregate_fn.is::<NanCount>() {
        return Some(Stat::NaNCount);
    }
    if aggregate_fn.is::<UncompressedSizeInBytes>() {
        return Some(Stat::UncompressedSizeInBytes);
    }

    tracing::trace!(
        "No legacy Stat slot for aggregate {}; stat expression will resolve to null",
        aggregate_fn
    );
    None
}