lance 8.0.0

A columnar data format that is 100x faster than Parquet for random access.
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// SPDX-License-Identifier: Apache-2.0
// SPDX-FileCopyrightText: Copyright The Lance Authors

use std::sync::Arc;

use lance_index::metrics::NoOpMetricsCollector;
use lance_index::scalar::lance_format::LanceIndexStore;
use lance_index::scalar::zonemap::ZoneMapIndex;
use lance_table::format::IndexMetadata;
use roaring::RoaringBitmap;
use uuid::Uuid;

use crate::{Dataset, Error, Result, dataset::index::LanceIndexStoreExt};

/// Merge one caller-defined group of source ZoneMap segments into a single segment.
pub(in crate::index) async fn merge_segments(
    dataset: &Dataset,
    segments: Vec<IndexMetadata>,
) -> Result<IndexMetadata> {
    if segments.is_empty() {
        return Err(Error::index("No segment metadata was provided".to_string()));
    }

    let field_id = *segments[0].fields.first().ok_or_else(|| {
        Error::invalid_input(format!(
            "CreateIndex: segment {} is missing field ids",
            segments[0].uuid
        ))
    })?;
    let field_path = dataset.schema().field_path(field_id)?;

    let mut scalar_indices = Vec::with_capacity(segments.len());
    let mut fragment_bitmap = RoaringBitmap::new();
    let dataset_fragments = dataset.fragment_bitmap.as_ref();
    for segment in &segments {
        let effective = segment
            .effective_fragment_bitmap(dataset_fragments)
            .ok_or_else(|| {
                Error::invalid_input(format!(
                    "CreateIndex: segment {} is missing fragment coverage",
                    segment.uuid
                ))
            })?;
        fragment_bitmap |= effective;
        let scalar_index =
            super::open_scalar_index(dataset, &field_path, segment, &NoOpMetricsCollector).await?;
        scalar_indices.push((segment.uuid, scalar_index));
    }

    let mut source_indices = Vec::with_capacity(scalar_indices.len());
    for (segment_uuid, scalar_index) in &scalar_indices {
        let zonemap_index = scalar_index
            .as_any()
            .downcast_ref::<ZoneMapIndex>()
            .ok_or_else(|| {
                Error::index(format!(
                    "merge_existing_index_segments: expected zonemap segment {}, got {:?}",
                    segment_uuid,
                    scalar_index.index_type()
                ))
            })?;
        source_indices.push(zonemap_index);
    }

    let new_uuid = Uuid::new_v4();
    let new_store = LanceIndexStore::from_dataset_for_new(dataset, &new_uuid)?;
    let created_index = lance_index::scalar::zonemap::merge_zonemap_indices(
        &source_indices,
        &new_store,
        &fragment_bitmap,
    )
    .await?;

    Ok(IndexMetadata {
        uuid: new_uuid,
        fields: vec![field_id],
        dataset_version: dataset.manifest.version,
        fragment_bitmap: Some(fragment_bitmap),
        index_details: Some(Arc::new(created_index.index_details)),
        index_version: created_index.index_version as i32,
        created_at: Some(chrono::Utc::now()),
        base_id: None,
        files: Some(created_index.files),
        ..segments[0].clone()
    })
}