Struct Config 

pub struct Config {

    pub tree_type: TreeType,
    pub level_count: u8,
    pub data_block_compression_policy: CompressionPolicy,
    pub index_block_compression_policy: CompressionPolicy,
    pub data_block_restart_interval_policy: RestartIntervalPolicy,
    pub index_block_restart_interval_policy: RestartIntervalPolicy,
    pub data_block_size_policy: BlockSizePolicy,
    pub index_block_size_policy: BlockSizePolicy,
    pub index_block_pinning_policy: PinningPolicy,
    pub filter_block_pinning_policy: PinningPolicy,
    pub data_block_hash_ratio_policy: HashRatioPolicy,
    pub filter_policy: FilterPolicy,
    pub blob_compression: CompressionType,
    /* private fields */
}

Tree configuration builder

Fields

tree_type: TreeType

Tree type (unused)

level_count: u8

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

Once set, the level count is fixed (in the “manifest” file)

data_block_compression_policy: CompressionPolicy

What type of compression is used for data blocks

index_block_compression_policy: CompressionPolicy

What type of compression is used for index blocks

data_block_restart_interval_policy: RestartIntervalPolicy

Restart interval inside data blocks

index_block_restart_interval_policy: RestartIntervalPolicy

Restart interval inside index blocks

data_block_size_policy: BlockSizePolicy

Block size of data blocks

index_block_size_policy: BlockSizePolicy

Block size of index blocks

index_block_pinning_policy: PinningPolicy

Whether to pin index blocks

filter_block_pinning_policy: PinningPolicy

Whether to pin filter blocks

data_block_hash_ratio_policy: HashRatioPolicy

Data block hash ratio

filter_policy: FilterPolicy

Filter construction policy

blob_compression: CompressionType

What type of compression is used for blobs

Implementations

impl Config

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

Initializes a new config

pub fn use_cache(self, cache: Arc<Cache>) -> Self

Sets the global cache.

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

Defaults to a cache with 8 MiB of capacity per tree.

pub fn expect_point_read_hits(self, b: bool) -> Self

If true, the last level will not build filters, reducing the filter size of a database by ~90% typically.

Enable this only if you know that point reads generally are expected to find a key-value pair.

pub fn filter_block_pinning_policy(self, policy: PinningPolicy) -> Self

Sets the pinning policy for filter blocks.

pub fn index_block_pinning_policy(self, policy: PinningPolicy) -> Self

Sets the pinning policy for index blocks.

pub fn data_block_restart_interval_policy( self, policy: RestartIntervalPolicy, ) -> Self

Sets the restart interval inside data blocks.

A higher restart interval saves space while increasing lookup times inside data blocks.

Default = 16

pub fn index_block_restart_interval_policy( self, policy: RestartIntervalPolicy, ) -> Self

Sets the restart interval inside index blocks.

A higher restart interval saves space while increasing lookup times inside index blocks.

Default = 1

pub fn filter_policy(self, policy: FilterPolicy) -> Self

Sets the filter construction policy.

pub fn data_block_compression_policy(self, policy: CompressionPolicy) -> Self

Sets the compression method for data blocks.

pub fn index_block_compression_policy(self, policy: CompressionPolicy) -> Self

Sets the compression method for index blocks.

pub fn blob_compression(self, compression: CompressionType) -> Self

Sets the blob compression method.

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

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

Defaults to 7, like LevelDB and RocksDB.

Cannot be changed once set.

Panics

Panics if n is 0.

pub fn data_block_size_policy(self, policy: BlockSizePolicy) -> Self

Sets the data block size policy.

pub fn index_block_size_policy(self, policy: BlockSizePolicy) -> Self

Sets the index block size policy.

pub fn data_block_hash_ratio_policy(self, policy: HashRatioPolicy) -> Self

Sets the hash ratio policy for data blocks.

If greater than 0.0, a hash index is embedded into data blocks that can speed up reads inside the data block.

pub fn blob_file_target_size(self, bytes: u64) -> Self

Sets the target size of blob files.

Smaller blob files allow more granular garbage collection which allows lower space amp for lower write I/O cost.

Larger blob files decrease the number of files on disk and maintenance overhead.

Defaults to 64 MiB.

This option has no effect when not used for opening a blob tree.

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

Sets the key-value separation threshold in bytes.

Smaller value will reduce compaction overhead and thus write amplification, at the cost of lower read performance.

Defaults to 4KiB.

This option has no effect when not used for opening a blob tree.

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

Opens a tree using the config.

Errors

Will return Err if an IO error occurs.

pub fn open_as_blob_tree(self) -> Result<BlobTree>

Opens a blob 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 duplicate 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.