vortex_array/
compress.rs

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use vortex_error::VortexResult;

use crate::aliases::hash_set::HashSet;
use crate::encoding::EncodingRef;
use crate::Array;

pub trait CompressionStrategy {
    fn compress(&self, array: &Array) -> VortexResult<Array>;

    fn used_encodings(&self) -> HashSet<EncodingRef>;
}

/// Check that compression did not alter the length of the validity array.
pub fn check_validity_unchanged(arr: &Array, compressed: &Array) {
    let _ = arr;
    let _ = compressed;
    #[cfg(debug_assertions)]
    {
        let old_validity = arr.with_dyn(|a| a.logical_validity().len());
        let new_validity = compressed.with_dyn(|a| a.logical_validity().len());

        debug_assert!(
            old_validity == new_validity,
            "validity length changed after compression: {old_validity} -> {new_validity}\n From tree {} To tree {}\n",
            arr.tree_display(),
            compressed.tree_display()
        );
    }
}

/// Check that compression did not alter the dtype
pub fn check_dtype_unchanged(arr: &Array, compressed: &Array) {
    let _ = arr;
    let _ = compressed;
    #[cfg(debug_assertions)]
    {
        use crate::ArrayDType;
        debug_assert!(
            arr.dtype() == compressed.dtype(),
            "Compression changed dtype: {} -> {}\nFrom array: {}Into array {}",
            arr.dtype(),
            compressed.dtype(),
            arr.tree_display(),
            compressed.tree_display(),
        );
    }
}