coordinode-lsm-tree 7.6.0

// SPDX-License-Identifier: Apache-2.0
// Copyright (c) 2026-present, Dmitry Prudnikov

//! A compaction into a level with a level below it ends its outputs on the
//! boundaries between the tables below: run as one stream, split into key
//! ranges run side by side, in the slices of a tight-space pass, and around a
//! row group it would copy whole.

use crate::{
    AbstractTree, AnyTree, Config, SequenceNumberCounter, Table, TableId,
    compaction::{Choice, CompactionStrategy, Input, state::CompactionState},
    version::Version,
};
use std::sync::Arc;
use test_log::test;

/// The target a flush cuts its tables at.
const FLUSH_TARGET: u64 = 40 << 10;

/// The target the merge under test cuts its outputs at.
const OUTPUT_TARGET: u64 = 64 << 10;

/// Moves exactly the named tables to a level.
struct Place(Vec<TableId>, u8);

impl CompactionStrategy for Place {
    fn get_name(&self) -> &'static str {
        "PlaceTest"
    }

    fn choose(&self, _: &Version, _: &Config, _: &CompactionState) -> Choice {
        Choice::Move(Input {
            table_ids: self.0.iter().copied().collect(),
            dest_level: self.1,
            canonical_level: self.1,
            target_size: u64::MAX,
        })
    }
}

/// Merges exactly the named tables into a level, at [`OUTPUT_TARGET`].
struct Merge(Vec<TableId>, u8);

impl CompactionStrategy for Merge {
    fn get_name(&self) -> &'static str {
        "MergeTest"
    }

    fn choose(&self, _: &Version, _: &Config, _: &CompactionState) -> Choice {
        Choice::Merge(self.input())
    }
}

impl Merge {
    fn input(&self) -> Input {
        Input {
            table_ids: self.0.iter().copied().collect(),
            dest_level: self.1,
            canonical_level: self.1,
            target_size: OUTPUT_TARGET,
        }
    }
}

fn key(i: u32) -> Vec<u8> {
    format!("k{i:06}").into_bytes()
}

fn index(key: &[u8]) -> u32 {
    std::str::from_utf8(key.get(1..).unwrap_or_default())
        .ok()
        .and_then(|digits| digits.parse().ok())
        .unwrap_or(u32::MAX)
}

/// A tree's configuration at `folder`, its files kept in memory: these tests
/// flush and move a hundred tables, which a real disk's syncs make slow.
fn in_memory(folder: &tempfile::TempDir) -> Config {
    Config::new(
        folder.path(),
        SequenceNumberCounter::default(),
        SequenceNumberCounter::default(),
    )
    .with_shared_fs(Arc::new(crate::fs::MemFs::new()))
}

fn open(config: Config) -> crate::Result<crate::Tree> {
    let AnyTree::Standard(tree) = config.table_target_size(FLUSH_TARGET).open()? else {
        panic!("expected a standard tree");
    };
    Ok(tree)
}

/// The tables of `level`, in key order.
fn tables(tree: &crate::Tree, level: usize) -> Vec<Table> {
    let version = tree.current_version();
    let mut tables: Vec<Table> = version
        .level(level)
        .into_iter()
        .flat_map(|level| level.iter())
        .flat_map(|run| run.iter())
        .cloned()
        .collect();
    tables.sort_by(|a, b| a.metadata.key_range.min().cmp(b.metadata.key_range.min()));
    tables
}

/// The index of the largest key of each of `tables`.
fn last_keys(tables: &[Table]) -> Vec<u32> {
    tables
        .iter()
        .map(|table| index(table.metadata.key_range.max()))
        .collect()
}

/// The boundaries between `tables` of one run: the last key of each but the
/// last.
fn boundaries_of(tables: &[Table]) -> Vec<u32> {
    let mut keys = last_keys(tables);
    keys.pop();
    keys
}

/// A `len`-byte value that does not compress, drawn from `seed`: outputs then
/// close on their size, where a compressible value would leave the writer's
/// held state to close them first.
fn noise(seed: u64, len: usize) -> Vec<u8> {
    let mut state = seed;
    let mut value: Vec<u8> = core::iter::repeat_with(|| {
        // splitmix64
        state = state.wrapping_add(0x9E37_79B9_7F4A_7C15);
        let mut z = state;
        z = (z ^ (z >> 30)).wrapping_mul(0xBF58_476D_1CE4_E5B9);
        z = (z ^ (z >> 27)).wrapping_mul(0x94D0_49BB_1331_11EB);
        (z ^ (z >> 31)).to_le_bytes()
    })
    .take(len.div_ceil(8))
    .flatten()
    .collect();
    value.truncate(len);
    value
}

/// Writes keys `keys` with incompressible `value_len`-byte values, flushes
/// them and moves the flushed run to `level`.
fn flush_into(
    tree: &crate::Tree,
    keys: core::ops::Range<u32>,
    value_len: usize,
    level: u8,
    seqno: &mut u64,
) -> crate::Result<()> {
    for i in keys {
        tree.insert(key(i), noise(*seqno, value_len), *seqno);
        *seqno += 1;
    }
    tree.flush_active_memtable(0)?;
    let ids = tables(tree, 0).iter().map(Table::id).collect();
    tree.compact(Arc::new(Place(ids, level)), 0)?;
    Ok(())
}

/// Level 3 holds keys `0..3000` in tables cut at another place than the
/// inputs', level 2 a part of the same keys and level 1 all of them; level 1
/// and level 2 are then merged into level 2. Returns the last key of each
/// output, the boundaries of level 3 and the largest key of each table level 2
/// held before the merge, where a split compaction's key ranges end.
fn merge_above_a_level(config: Config) -> crate::Result<(Vec<u32>, Vec<u32>, Vec<u32>)> {
    let tree = open(config)?;
    let mut seqno = 1;
    flush_into(&tree, 0..3_000, 700, 3, &mut seqno)?;
    flush_into(&tree, 1_000..2_000, 1_000, 2, &mut seqno)?;
    flush_into(&tree, 0..3_000, 1_000, 1, &mut seqno)?;

    let boundaries = boundaries_of(&tables(&tree, 3));
    let seams = last_keys(&tables(&tree, 2));
    let ids = tables(&tree, 1)
        .iter()
        .chain(tables(&tree, 2).iter())
        .map(Table::id)
        .collect();
    tree.compact(Arc::new(Merge(ids, 2)), 0)?;

    for i in 0..3_000 {
        assert!(tree.get(key(i), crate::SeqNo::MAX)?.is_some(), "key {i}");
    }
    Ok((last_keys(&tables(&tree, 2)), boundaries, seams))
}

/// A merge run as one stream ends every output but its last on a boundary of
/// the level below.
#[test]
fn a_serial_merge_ends_its_outputs_on_the_level_below() -> crate::Result<()> {
    let folder = tempfile::tempdir()?;
    let config = in_memory(&folder).compaction_threads(1);
    let (outputs, boundaries, _) = merge_above_a_level(config)?;
    assert!(outputs.len() > 3, "{} outputs", outputs.len());
    let (_, cut) = outputs.split_last().unwrap();
    for last in cut {
        assert!(
            boundaries.contains(last),
            "an output ends at {last}: outputs end at {outputs:?}, the level below at {boundaries:?}"
        );
    }
    Ok(())
}

/// A merge into a level whose next level is empty aligns to the first level
/// below that holds tables: its outputs move down through the empty levels
/// untouched and are next merged there, as an intra-L0 merge's outputs are
/// merged into the base level.
#[test]
fn a_merge_above_an_empty_level_ends_its_outputs_on_the_next_level_holding_tables()
-> crate::Result<()> {
    let folder = tempfile::tempdir()?;
    let tree = open(in_memory(&folder).compaction_threads(1))?;
    let mut seqno = 1;
    flush_into(&tree, 0..3_000, 700, 3, &mut seqno)?;
    flush_into(&tree, 0..3_000, 1_000, 1, &mut seqno)?;
    assert!(
        tables(&tree, 2).is_empty(),
        "the level below the merge is empty"
    );
    let boundaries = boundaries_of(&tables(&tree, 3));
    let ids = tables(&tree, 1).iter().map(Table::id).collect();
    tree.compact(Arc::new(Merge(ids, 1)), 0)?;

    let outputs = last_keys(&tables(&tree, 1));
    assert!(outputs.len() > 3, "{} outputs", outputs.len());
    let (_, cut) = outputs.split_last().unwrap();
    for last in cut {
        assert!(
            boundaries.contains(last),
            "an output ends at {last}: outputs end at {outputs:?}, L3 at {boundaries:?}"
        );
    }
    Ok(())
}

/// A size-tiered merge writes back into L0, where its outputs are next merged
/// with other L0 runs: tables below L0 give it no boundaries, and its outputs
/// are cut where they would be with alignment off.
#[test]
fn a_size_tiered_merge_is_not_aligned_to_the_levels_below() -> crate::Result<()> {
    let run = |aligned: bool| -> crate::Result<Vec<u32>> {
        let folder = tempfile::tempdir()?;
        let tree = open(
            in_memory(&folder)
                .compaction_threads(1)
                .compaction_output_alignment(aligned),
        )?;
        let mut seqno = 1;
        flush_into(&tree, 0..3_000, 700, 3, &mut seqno)?;
        // Four L0 runs of one size: a size-tiered merge of all of them.
        for _ in 0..4 {
            for i in 0..1_000 {
                tree.insert(key(i * 3), noise(seqno, 1_000), seqno);
                seqno += 1;
            }
            tree.flush_active_memtable(0)?;
        }
        let strategy =
            crate::compaction::SizeTiered::default().with_table_target_size(OUTPUT_TARGET);
        tree.compact(Arc::new(strategy), 0)?;
        assert_eq!(
            tree.current_version()
                .level(0)
                .map_or(0, |level| level.run_count()),
            1,
            "the four runs were merged"
        );
        Ok(last_keys(&tables(&tree, 0)))
    };
    assert_eq!(run(true)?, run(false)?);
    Ok(())
}

/// A level holding two overlapping runs has no boundary inside their overlap:
/// an output ending there would reach a table of each run. Every boundary lies
/// where no table of either run spans it, and the runs' tables outside the
/// overlap still give theirs.
#[test]
fn overlapping_runs_give_no_boundary_inside_a_table_of_either() -> crate::Result<()> {
    let folder = tempfile::tempdir()?;
    let tree = open(in_memory(&folder))?;
    // Two flushes stay in L0 as two runs over overlapping keys.
    let mut seqno = 1;
    for keys in [0..1_800, 1_200..3_000] {
        for i in keys {
            tree.insert(key(i), noise(seqno, 700), seqno);
            seqno += 1;
        }
        tree.flush_active_memtable(0)?;
    }
    let version = tree.current_version();
    let Some(level) = version.level(0) else {
        panic!("L0 exists");
    };
    assert_eq!(level.run_count(), 2, "two overlapping runs");
    let mut all: Vec<&Table> = level.iter().flat_map(|run| run.iter()).collect();
    all.sort_by(|a, b| a.metadata.key_range.min().cmp(b.metadata.key_range.min()));
    let spans: Vec<(u32, u32)> = all
        .iter()
        .map(|t| {
            (
                index(t.metadata.key_range.min()),
                index(t.metadata.key_range.max()),
            )
        })
        .collect();

    let boundaries: Vec<u32> = crate::compaction::flavour::boundaries_between(
        all.iter().copied(),
        all.len() - 1,
        &crate::comparator::DefaultUserComparator,
    )
    .iter()
    .map(|boundary| index(&boundary.key))
    .collect();
    assert!(
        boundaries.iter().any(|&b| b < 1_200) && boundaries.iter().any(|&b| b >= 1_800),
        "the tables outside the overlap give boundaries: {boundaries:?}"
    );
    for &b in &boundaries {
        assert!(
            !spans.iter().any(|&(min, max)| min <= b && b < max),
            "a boundary at {b} lies inside a table: {spans:?}"
        );
    }
    Ok(())
}

/// Past a boundary of a level holding overlapping runs lies a cluster of
/// tables, not one: an output reaching past the boundary has the next merge
/// read every table of the cluster it reaches, and the boundary carries each.
#[cfg(feature = "columnar")]
#[test]
fn a_boundary_before_overlapping_runs_carries_every_table_it_reaches() -> crate::Result<()> {
    let folder = tempfile::tempdir()?;
    let tree = open(in_memory(&folder))?;
    let mut seqno = 1;
    for keys in [0..1_800, 1_200..3_000] {
        for i in keys {
            tree.insert(key(i), noise(seqno, 700), seqno);
            seqno += 1;
        }
        tree.flush_active_memtable(0)?;
    }
    let version = tree.current_version();
    let Some(level) = version.level(0) else {
        panic!("L0 exists");
    };
    let mut all: Vec<&Table> = level.iter().flat_map(|run| run.iter()).collect();
    all.sort_by(|a, b| a.metadata.key_range.min().cmp(b.metadata.key_range.min()));

    let cmp = crate::comparator::DefaultUserComparator;
    let boundaries =
        crate::compaction::flavour::boundaries_between(all.iter().copied(), all.len() - 1, &cmp);
    let mut largest_cluster = 0;
    for (at, boundary) in boundaries.iter().enumerate() {
        let next = boundaries.get(at + 1).map(|next| index(&next.key));
        let cluster: Vec<(u32, u64)> = all
            .iter()
            .map(|t| (index(t.metadata.key_range.min()), t.file_size()))
            .filter(|&(min, _)| min > index(&boundary.key) && next.is_none_or(|next| min <= next))
            .collect();
        let carried: Vec<(u32, u64)> = boundary
            .after
            .iter()
            .map(|(min, bytes)| (index(min), *bytes))
            .collect();
        assert_eq!(carried, cluster, "the tables past {}", index(&boundary.key));
        largest_cluster = largest_cluster.max(cluster.len());

        for &(end, _) in &cluster {
            let reached: u64 = cluster
                .iter()
                .filter(|&&(min, _)| min <= end)
                .map(|&(_, bytes)| bytes)
                .sum();
            assert_eq!(
                boundary.reached_bytes(&key(end), &cmp),
                reached,
                "an output past {} ending at {end}",
                index(&boundary.key)
            );
        }
        let &(first_min, _) = cluster.first().unwrap();
        assert_eq!(
            boundary.reached_bytes(&key(first_min - 1), &cmp),
            0,
            "an output ending in the gap before the cluster reaches none of it"
        );
    }
    assert!(
        largest_cluster > 1,
        "the overlap puts tables of both runs past one boundary"
    );
    Ok(())
}

/// The written work of a merge is the bytes of the tables it installs, in its
/// own report and in the tree's counter, and a move, which writes none,
/// leaves the counter as it was.
#[cfg(feature = "metrics")]
#[test]
fn compaction_work_written_counts_the_tables_a_merge_installs() -> crate::Result<()> {
    let folder = tempfile::tempdir()?;
    let tree = open(in_memory(&folder))?;
    let mut seqno = 1;
    flush_into(&tree, 0..1_000, 1_000, 1, &mut seqno)?;
    assert_eq!(
        tree.metrics().compaction_work_measured().written,
        0,
        "a move writes nothing"
    );
    let ids = tables(&tree, 1).iter().map(Table::id).collect();
    let result = tree.compact(Arc::new(Merge(ids, 2)), 0)?;
    let installed: u64 = tables(&tree, 2).iter().map(Table::file_len).sum();
    assert!(installed > 0);
    assert_eq!(result.work.measured.written, installed);
    assert_eq!(tree.metrics().compaction_work_measured().written, installed);
    Ok(())
}

/// A merge split into key ranges ends every output on a boundary of the level
/// below, as the stream does, or where its range ends. In a range with no
/// boundary left before its end, an output ends at the target: no boundary
/// would come to end it on.
#[test]
fn a_split_merge_ends_its_outputs_on_the_level_below_or_its_range() -> crate::Result<()> {
    let folder = tempfile::tempdir()?;
    let config = in_memory(&folder)
        .compaction_threads(4)
        .subcompaction_min_bytes(0);
    let (outputs, boundaries, seams) = merge_above_a_level(config)?;
    let (_, cut) = outputs.split_last().unwrap();
    let mut at_boundaries = 0;
    for &last in cut {
        if boundaries.contains(&last) {
            at_boundaries += 1;
            continue;
        }
        if seams.contains(&last) {
            continue;
        }
        // A range ends on the first seam at or past its keys.
        let range_end = seams.iter().copied().find(|&seam| seam > last);
        assert!(
            !boundaries
                .iter()
                .any(|&b| b > last && range_end.is_none_or(|end| b < end)),
            "an output ends at {last} with a boundary still ahead in its range: outputs end \
             at {outputs:?}, the level below at {boundaries:?}, ranges at {seams:?}"
        );
    }
    assert!(at_boundaries > 0, "the ranges' outputs end on boundaries");
    Ok(())
}

/// With alignment off the same merge cuts at the target alone: outputs end
/// where the size says, which is not where the level below divides.
#[test]
fn without_alignment_outputs_end_off_the_level_below() -> crate::Result<()> {
    let folder = tempfile::tempdir()?;
    let config = in_memory(&folder)
        .compaction_threads(1)
        .compaction_output_alignment(false);
    let (outputs, boundaries, _) = merge_above_a_level(config)?;
    let (_, cut) = outputs.split_last().unwrap();
    assert!(
        cut.iter().any(|last| !boundaries.contains(last)),
        "a cut at the target alone lands off the level below"
    );
    Ok(())
}

/// The slices of a tight-space pass end their outputs on the boundaries of the
/// level below as one stream does. An output ends off one only where no
/// boundary is left before its slice ends: at the slice's end, or at the
/// target with no boundary left to wait for.
#[cfg(feature = "std")]
#[test]
fn tight_space_slices_end_their_outputs_on_the_level_below() -> crate::Result<()> {
    use crate::fs::{Fault, FaultFs, FaultOp, FaultRule};

    // What the quota leaves past the tree's footprint: the budget of a slice,
    // a fraction of the merge's output.
    const HEADROOM: u64 = 256 << 10;

    let folder = tempfile::tempdir()?;
    let mem = crate::fs::MemFs::with_capacity(u64::MAX);
    let faulty = FaultFs::new(mem.clone());
    // Free space reads as unknown, so the quota alone constrains the merge.
    faulty.injector().arm(FaultRule::new(
        FaultOp::AvailableSpace,
        Fault::Error(crate::io::ErrorKind::Unsupported),
    ));
    let AnyTree::Standard(tree) = Config::new(
        folder.path(),
        SequenceNumberCounter::default(),
        SequenceNumberCounter::default(),
    )
    .with_shared_fs(Arc::new(faulty))
    .compaction_threads(1)
    .open()?
    else {
        panic!("expected a standard tree");
    };
    let mut seqno = 1;
    for start in (0..3_000).step_by(30) {
        flush_into(&tree, start..start + 30, 700, 3, &mut seqno)?;
    }
    // One table above: the space gate finds no narrower merge that fits.
    flush_into(&tree, 0..3_000, 1_000, 1, &mut seqno)?;
    let inputs = tables(&tree, 1);
    assert_eq!(inputs.len(), 1, "the merge reads one table");
    let boundaries = boundaries_of(&tables(&tree, 3));
    // The slices as the pass cuts them: free space unknown, so the quota caps
    // them, and their outputs cut on the level below at the merge's target.
    let merge = Merge(inputs.iter().map(Table::id).collect(), 2);
    let payload = merge.input();
    let opts = super::Options::from_tree(&tree, Arc::new(Merge(merge.0.clone(), merge.1)));
    let cut_keys =
        crate::compaction::flavour::output_cut_keys(&tree.current_version(), &opts, &payload);
    let caps = super::SliceCaps {
        tables: u64::MAX,
        blobs: u64::MAX,
        total: HEADROOM,
    };
    let outputs = super::SliceOutputs {
        target_size: OUTPUT_TARGET,
        cut_keys: &cut_keys,
    };
    let slice_ends: Vec<u32> = super::tight_slices(
        &inputs,
        caps,
        &outputs,
        None,
        &tree.config.comparator,
        &super::input_pacer(&opts),
    )?
    .iter()
    .filter_map(|slice| slice.end.as_ref())
    .map(|end| index(end))
    .collect();
    assert!(
        slice_ends.len() > 2,
        "the pass runs in slices: {slice_ends:?}"
    );

    let used = crate::storage_stats::compute_used_bytes(&tree.current_version())?;
    tree.update_runtime_config(|cfg| {
        cfg.storage_admission_check = true;
        cfg.tight_space_compaction = true;
        cfg.storage_limit_bytes = Some(used + HEADROOM);
    })?;
    // Held through the pass, the input would keep each slice's consumed
    // prefix from being reclaimed, and the pass would stop after one.
    let input_ids = inputs.iter().map(Table::id).collect();
    drop(inputs);
    tree.compact(Arc::new(Merge(input_ids, 2)), 0)?;
    assert!(
        mem.punched_bytes() > 0,
        "the merge ran as a tight-space pass"
    );
    for i in 0..3_000 {
        assert!(tree.get(key(i), crate::SeqNo::MAX)?.is_some(), "key {i}");
    }

    let outputs = last_keys(&tables(&tree, 2));
    let (_, cut) = outputs.split_last().unwrap();
    let mut at_boundaries = 0;
    for &last in cut {
        if boundaries.contains(&last) {
            at_boundaries += 1;
            continue;
        }
        // A slice holds the keys below its end key.
        let slice_end = slice_ends.iter().copied().find(|&end| end > last);
        assert!(
            !boundaries
                .iter()
                .any(|&b| b > last && slice_end.is_none_or(|end| b < end)),
            "an output ends at {last} with a boundary still ahead in its slice: outputs end at \
             {outputs:?}, the level below at {boundaries:?}, slices at {slice_ends:?}"
        );
    }
    assert!(at_boundaries > 0, "the slices' outputs end on boundaries");
    Ok(())
}

/// A columnar table merged whole into a level above another: its row groups
/// are copied, but one holding a boundary of the level below between its keys
/// is written key by key once the output may end there, since its bytes cost
/// less than the table the output would otherwise straddle. With alignment off
/// every group is copied.
#[cfg(all(feature = "columnar", feature = "metrics"))]
#[test]
fn a_group_holding_a_boundary_is_written_so_the_output_ends_on_it() -> crate::Result<()> {
    use crate::config::{BlockSizePolicy, CompressionPolicy};

    let run = |aligned: bool| -> crate::Result<(u64, u64, Vec<u32>, Vec<u32>)> {
        let folder = tempfile::tempdir()?;
        let tree = open(
            in_memory(&folder)
                .columnar_row_group_size_policy(BlockSizePolicy::all(4 * 1_024))
                .compaction_threads(1)
                .compaction_output_alignment(aligned),
        )?;
        tree.update_runtime_config(|cfg| {
            cfg.columnar = true;
            cfg.zone_map = true;
            cfg.data_block_compression_policy =
                CompressionPolicy::all(crate::CompressionType::None);
        })?;
        let mut seqno = 1;
        // Tables of 30 keys below: every other boundary falls between two keys
        // of a 4-row group above, once the output holds 28 rows, past half
        // its target, and before the writer's held state closes it.
        for start in (0..3_000).step_by(30) {
            flush_into(&tree, start..start + 30, 700, 3, &mut seqno)?;
        }
        flush_into(&tree, 0..3_000, 1_000, 1, &mut seqno)?;
        let groups_in: u64 = tables(&tree, 1)
            .iter()
            .map(|table| table.metadata.data_block_count)
            .sum();
        let boundaries = boundaries_of(&tables(&tree, 3));
        let ids = tables(&tree, 1).iter().map(Table::id).collect();
        tree.compact(Arc::new(Merge(ids, 2)), 0)?;
        for i in 0..3_000 {
            assert!(tree.get(key(i), crate::SeqNo::MAX)?.is_some(), "key {i}");
        }
        Ok((
            groups_in,
            tree.metrics().compaction_groups_carried(),
            last_keys(&tables(&tree, 2)),
            boundaries,
        ))
    };

    let (groups_in, carried, _, _) = run(false)?;
    assert_eq!(
        carried, groups_in,
        "without alignment every group is copied"
    );

    let (groups_in, carried, outputs, boundaries) = run(true)?;
    assert!(carried > 0, "the groups holding no boundary are copied");
    assert!(
        carried < groups_in,
        "{carried} of {groups_in} groups copied, those an output ends inside included: outputs \
         end at {outputs:?}, the level below at {boundaries:?}"
    );
    let (_, cut) = outputs.split_last().unwrap();
    for last in cut {
        assert!(
            boundaries.contains(last),
            "an output ends at {last}: outputs end at {outputs:?}, the level below at \
             {boundaries:?}"
        );
    }
    Ok(())
}