Struct SuperVersion 

pub struct SuperVersion {
    pub version_number: u64,
    pub memtable_version: u64,
    pub immutable_memtables: Arc<Vec<ImmutableMemTableRef>>,
    pub levels: Arc<Vec<LevelMetadata>>,
    pub min_snapshot_seqno: u64,
    pub log_number: u64,
    pub prev_log_number: u64,
    pub next_file_number: u64,
    pub manifest_file_number: u64,
}

SuperVersion: A consistent snapshot of all storage metadata

This is the key abstraction for lock-free reads. A SuperVersion contains Arc references to:

• Current mutable memtable
• List of immutable memtables (pending flush)
• All SSTable levels and their file metadata

Readers acquire a SuperVersion (O(1) atomic load), use it for their entire read operation, then release it (O(1) Arc drop). No locks required.

Writers create a new SuperVersion with modified metadata and atomically swap it in. Old versions remain valid until all readers release them.

Fields

version_number: u64

Version number (monotonically increasing)

memtable_version: u64

Current mutable memtable reference Note: The memtable itself may have internal synchronization, but the reference is immutable within a SuperVersion

immutable_memtables: Arc<Vec<ImmutableMemTableRef>>

Immutable memtables (oldest first)

levels: Arc<Vec<LevelMetadata>>

SSTable levels (L0, L1, L2, …)

min_snapshot_seqno: u64

Minimum sequence number safe to garbage collect Versions with seqno < this can be pruned during compaction

log_number: u64

Current log (WAL) number for crash recovery

prev_log_number: u64

Prev log number (for two-log protocol during flush)

next_file_number: u64

Next file number to allocate

manifest_file_number: u64

Manifest file number

Implementations

impl SuperVersion

pub fn new() -> Self

Create a new empty SuperVersion

pub fn with_new_immutable(&self, imm: ImmutableMemTableRef) -> Self

Create a new SuperVersion with updated immutable memtables

pub fn with_flushed_memtables( &self, flushed_ids: &[u64], new_files: Vec<(u32, Arc<FileMetadata>)>, ) -> Self

Create a new SuperVersion after flushing immutable memtables

pub fn with_compaction_result( &self, input_files: &[(u32, u64)], output_files: Vec<(u32, Arc<FileMetadata>)>, ) -> Self

Create a new SuperVersion after compaction

pub fn total_file_count(&self) -> usize

Get total number of files across all levels

pub fn pick_compaction_level(&self) -> Option<u32>

Get level with highest compaction score

Trait Implementations

impl Clone for SuperVersion

fn clone(&self) -> SuperVersion

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for SuperVersion

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for SuperVersion

fn default() -> Self

Returns the “default value” for a type.