builder.rs

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

//! Builder for configuring `BtrBlocksCompressor` instances.

use vortex_utils::aliases::hash_set::HashSet;

use crate::BtrBlocksCompressor;
use crate::CascadingCompressor;
use crate::Scheme;
use crate::SchemeExt;
use crate::SchemeId;
use crate::schemes::bool;
use crate::schemes::decimal;
use crate::schemes::float;
use crate::schemes::integer;
use crate::schemes::rle;
use crate::schemes::string;
use crate::schemes::temporal;

/// All available compression schemes.
///
/// This list is order-sensitive: the builder preserves this order when constructing
/// the final scheme list, so that tie-breaking is deterministic.
pub const ALL_SCHEMES: &[&dyn Scheme] = &[
    ////////////////////////////////////////////////////////////////////////////////////////////////
    // Bool schemes.
    ////////////////////////////////////////////////////////////////////////////////////////////////
    &bool::BoolConstantScheme,
    ////////////////////////////////////////////////////////////////////////////////////////////////
    // Integer schemes.
    ////////////////////////////////////////////////////////////////////////////////////////////////
    &integer::IntConstantScheme,
    // NOTE: FoR must precede BitPacking to avoid unnecessary patches.
    &integer::FoRScheme,
    // NOTE: ZigZag should precede BitPacking because we don't want negative numbers.
    &integer::ZigZagScheme,
    &integer::BitPackingScheme,
    &integer::SparseScheme,
    &integer::IntDictScheme,
    &integer::RunEndScheme,
    &integer::SequenceScheme,
    &rle::RLE_INTEGER_SCHEME,
    ////////////////////////////////////////////////////////////////////////////////////////////////
    // Float schemes.
    ////////////////////////////////////////////////////////////////////////////////////////////////
    &float::FloatConstantScheme,
    &float::ALPScheme,
    &float::ALPRDScheme,
    &float::FloatDictScheme,
    &float::NullDominatedSparseScheme,
    &rle::RLE_FLOAT_SCHEME,
    ////////////////////////////////////////////////////////////////////////////////////////////////
    // String schemes.
    ////////////////////////////////////////////////////////////////////////////////////////////////
    &string::StringDictScheme,
    &string::FSSTScheme,
    &string::StringConstantScheme,
    &string::NullDominatedSparseScheme,
    // Decimal schemes.
    &decimal::DecimalScheme,
    // Temporal schemes.
    &temporal::TemporalScheme,
];

/// Builder for creating configured [`BtrBlocksCompressor`] instances.
///
/// By default, all schemes in [`ALL_SCHEMES`] are enabled. Feature-gated schemes (Pco, Zstd)
/// are not in `ALL_SCHEMES` and must be added explicitly via
/// [`with_new_scheme`](BtrBlocksCompressorBuilder::with_new_scheme) or
/// [`with_compact`](BtrBlocksCompressorBuilder::with_compact).
///
/// # Examples
///
/// ```rust
/// use vortex_btrblocks::{BtrBlocksCompressorBuilder, Scheme, SchemeExt};
/// use vortex_btrblocks::schemes::integer::IntDictScheme;
///
/// // Default compressor with all schemes in ALL_SCHEMES.
/// let compressor = BtrBlocksCompressorBuilder::default().build();
///
/// // Exclude specific schemes.
/// let compressor = BtrBlocksCompressorBuilder::default()
///     .exclude([IntDictScheme.id()])
///     .build();
/// ```
#[derive(Debug, Clone)]
pub struct BtrBlocksCompressorBuilder {
    schemes: Vec<&'static dyn Scheme>,
}

impl Default for BtrBlocksCompressorBuilder {
    fn default() -> Self {
        Self {
            schemes: ALL_SCHEMES.to_vec(),
        }
    }
}

impl BtrBlocksCompressorBuilder {
    /// Adds an external compression scheme not in [`ALL_SCHEMES`].
    ///
    /// This allows encoding crates outside of `vortex-btrblocks` to register their own schemes with
    /// the compressor.
    ///
    /// # Panics
    ///
    /// Panics if a scheme with the same [`SchemeId`] is already present.
    pub fn with_new_scheme(mut self, scheme: &'static dyn Scheme) -> Self {
        assert!(
            !self.schemes.iter().any(|s| s.id() == scheme.id()),
            "scheme {:?} is already present in the builder",
            scheme.id(),
        );

        self.schemes.push(scheme);
        self
    }

    /// Adds compact encoding schemes (Zstd for strings, Pco for numerics).
    ///
    /// This provides better compression ratios than the default, especially for floating-point
    /// heavy datasets. Requires the `zstd` feature. When the `pco` feature is also enabled,
    /// Pco schemes for integers and floats are included.
    ///
    /// # Panics
    ///
    /// Panics if any of the compact schemes are already present.
    #[cfg(feature = "zstd")]
    pub fn with_compact(self) -> Self {
        // This should be fast since we don't have that many schemes.
        let builder = self.with_new_scheme(&string::ZstdScheme);

        #[cfg(feature = "pco")]
        let builder = builder
            .with_new_scheme(&integer::PcoScheme)
            .with_new_scheme(&float::PcoScheme);

        builder
    }

    /// Excludes the specified compression schemes by their [`SchemeId`].
    pub fn exclude(mut self, ids: impl IntoIterator<Item = SchemeId>) -> Self {
        let ids: HashSet<_> = ids.into_iter().collect();
        self.schemes.retain(|s| !ids.contains(&s.id()));
        self
    }

    /// Builds the configured [`BtrBlocksCompressor`].
    pub fn build(self) -> BtrBlocksCompressor {
        BtrBlocksCompressor(CascadingCompressor::new(self.schemes))
    }
}