Function compact_commit

nodedb/src/engine/sparse/fts_redb/backend/segments.rs:121–154

Atomically register a new merged segment and remove the source segments that were merged into it. Performing the write and all removals in one redb write transaction ensures the operation is crash-safe: a crash mid-compaction leaves the old segments intact (a subsequent maintenance cycle will retry), and there is never a window where both the old and the new segments coexist on a reader that open

(
    backend: &RedbFtsBackend,
    tid: u64,
    collection: &str,
    new_segment_id: &str,
    new_segment_data: &[u8],
    merged_ids: &[String],
)

/// there is never a window where both the old and the new segments coexist
/// on a reader that opens a concurrent read transaction.
pub(super) fn compact_commit(
    backend: &RedbFtsBackend,
    tid: u64,
    collection: &str,
    new_segment_id: &str,
    new_segment_data: &[u8],
    merged_ids: &[String],
) -> crate::Result<()> {
    let write_txn = backend
        .db
        .begin_write()
        .map_err(|e| redb_err("compact txn", e))?;
    {
        let mut table = write_txn
            .open_table(SEGMENTS)
            .map_err(|e| redb_err("open segments for compact", e))?;
        table
            .insert((tid, collection, new_segment_id), new_segment_data)
            .map_err(|e| redb_err("insert merged segment", e))?;
        for id in merged_ids {
            // Propagate remove errors so a failed source-segment removal aborts
            // the entire transaction; otherwise we would commit a state in
            // which both old and new segments are visible to readers, causing
            // double-counted postings during BM25 scoring.
            table
                .remove((tid, collection, id.as_str()))
                .map_err(|e| redb_err("remove merged source segment", e))?;
        }
    }
    write_txn
        .commit()
        .map_err(|e| redb_err("compact txn commit", e))?;
    Ok(())
}

/// Enumerate all `(tid, collection)` pairs that have at least one segment
/// stored in the SEGMENTS table.