Struct Environment

pub struct Environment { /* private fields */ }

Available on crate feature mdbx only.

An environment supports multiple databases, all residing in the same shared-memory map.

Accessing the environment is thread-safe. The environment will be closed when the last instance of this type is dropped.

Implementations

impl Environment

pub fn builder() -> EnvironmentBuilder

Creates a new builder for specifying options for opening an MDBX environment.

pub fn is_write_map(&self) -> bool

Returns true if the environment was opened as WRITEMAP.

pub fn env_kind(&self) -> EnvironmentKind

Returns the kind of the environment.

pub fn is_read_write(&self) -> Result<bool, Error>

Returns true if the environment was opened in crate::Mode::ReadWrite mode.

pub fn is_read_only(&self) -> Result<bool, Error>

Returns true if the environment was opened in crate::Mode::ReadOnly mode.

pub fn timed_out_not_aborted_transactions(&self) -> usize

Available on crate feature read-tx-timeouts only.

Returns the number of timed out transactions that were not aborted by the user yet.

pub fn begin_ro_txn(&self) -> Result<Transaction<RO>, Error>

Create a read-only transaction for use with the environment.

pub fn begin_rw_txn(&self) -> Result<Transaction<RW>, Error>

Create a read-write transaction for use with the environment. This method will block while there are any other read-write transactions open on the environment.

pub fn sync(&self, force: bool) -> Result<bool, Error>

Flush the environment data buffers to disk.

pub fn stat(&self) -> Result<Stat, Error>

Retrieves statistics about this environment.

pub fn info(&self) -> Result<Info, Error>

Retrieves info about this environment.

pub fn freelist(&self) -> Result<usize, Error>

Retrieves the total number of pages on the freelist.

Along with Environment::info(), this can be used to calculate the exact number of used pages as well as free pages in this environment.

let dir = tempfile::tempdir().unwrap();
let env = Environment::builder().open(dir.path()).unwrap();
let info = env.info().unwrap();
let stat = env.stat().unwrap();
let freelist = env.freelist().unwrap();
let last_pgno = info.last_pgno() + 1; // pgno is 0 based.
let total_pgs = info.map_size() / stat.page_size() as usize;
let pgs_in_use = last_pgno - freelist;
let pgs_free = total_pgs - pgs_in_use;

Note:

• MDBX stores all the freelists in the designated database 0 in each environment, and the freelist count is stored at the beginning of the value as uint32_t in the native byte order.

• It will create a read transaction to traverse the freelist database.

Trait Implementations

impl Clone for Environment

fn clone(&self) -> Environment

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Environment

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

Formats the value using the given formatter.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 8 bytes