Struct lsm_tree::Config

pub struct Config {
    pub path: PathBuf,
    pub block_size: u32,
    pub block_cache: Arc<BlockCache>,
    pub max_memtable_size: u32,
    pub level_count: u8,
    pub level_ratio: u8,
    pub flush_threads: u8,
    pub fsync_ms: Option<usize>,
    /* private fields */
}

Tree configuration

Fields

path: PathBuf

Folder path

block_size: u32

Block size of data and index blocks

block_cache: Arc<BlockCache>

Block cache

max_memtable_size: u32

Maximum size in bytes of the write buffer

level_count: u8

Amount of levels of the LSM tree (depth of tree)

level_ratio: u8

Size ratio between levels of the LSM tree (a.k.a fanout, growth rate).

This is the exponential growth of the from one level to the next

A level target size is: max_memtable_size * level_ratio.pow(#level + 1)

flush_threads: u8

Maximum amount of concurrent flush threads

fsync_ms: Option<usize>

Starts a thread that will periodically fsync the journals for durability

Implementations

impl Config

pub fn new<P: AsRef<Path>>(path: P) -> Self

Initializes a new config

pub fn fsync_ms(self, ms: Option<usize>) -> Self

Starts a thread that will periodically fsync the journal for durability.

That means in case of a fatal crash (not proper unwind) at most the last ms of data may be lost. Without fsyncing, your data is at the mercy of your operating system’s syncing logic. If you want to make sure a write is definitely durable, call Tree::flush manually after writing. Flushing after every write has dramatic performance implications (100x-1000x slower for SSDs). Even when disabled, the tree will always try to fsync when it is being dropped.

Defaults to 1 second.

Panics

Panics if ms is below 100.

pub fn flush_threads(self, count: u8) -> Self

Maximum amount of concurrent flush threads.

You may want to increase this the more CPU cores you have.

Defaults to 4.

Panics

Panics if count is 0.

pub fn level_count(self, n: u8) -> Self

Sets the amount of levels of the LSM tree (depth of tree).

Defaults to 7, like LevelDB and RocksDB.

Panics

Panics if n is 0.

pub fn level_ratio(self, n: u8) -> Self

Sets the size ratio between levels of the LSM tree (a.k.a. fanout, growth rate).

Defaults to 10.

Panics

Panics if n is less than 2.

pub fn max_memtable_size(self, bytes: u32) -> Self

Sets the maximum memtable size.

Defaults to 16 MiB.

pub fn block_size(self, block_size: u32) -> Self

Sets the block size.

Defaults to 4 KiB (4096 bytes).

Panics

Panics if the block size is smaller than 1 KiB (1024 bytes).

pub fn block_cache(self, block_cache: Arc<BlockCache>) -> Self

Sets the block cache.

You can create a global BlockCache and share it between multiple trees to cap global cache memory usage.

Defaults to a block cache with 16 MiB of capacity per tree.

pub fn compaction_strategy( self, strategy: Arc<dyn CompactionStrategy + Send + Sync> ) -> Self

Sets the compaction strategy to use.

Defaults to compaction::Levelled

pub fn open(self) -> Result<Tree>

Opens a tree using the config.

Errors

Will return Err if an IO error occurs.

Trait Implementations

impl Clone for Config

fn clone(&self) -> Config

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Default for Config

fn default() -> Self

Returns the “default value” for a type.