Struct libmdbx::Environment

pub struct Environment<E> where
    E: EnvironmentKind,  { /* private fields */ }

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

Implementations

impl<E> Environment<E> where
    E: EnvironmentKind, 

pub fn new() -> EnvironmentBuilder<E>

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

pub fn env(&self) -> *mut MDBX_env

Returns a raw pointer to the underlying MDBX environment.

The caller must ensure that the pointer is not dereferenced after the lifetime of the environment.

pub fn begin_ro_txn(&self) -> Result<Transaction<'_, RO, E>>

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

pub fn begin_rw_txn(&self) -> Result<Transaction<'_, RW, E>>

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>

Flush the environment data buffers to disk.

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

Retrieves statistics about this environment.

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

Retrieves info about this environment.

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

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::<NoWriteMap>::new().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:

• LMDB 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 libc::size_t in the native byte order.

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

Trait Implementations

impl<E> Debug for Environment<E> where
    E: EnvironmentKind, 

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

Formats the value using the given formatter.

impl<E> Drop for Environment<E> where
    E: EnvironmentKind, 

fn drop(&mut self)

Executes the destructor for this type.

impl<E> Send for Environment<E> where
    E: EnvironmentKind, 

impl<E> Sync for Environment<E> where
    E: EnvironmentKind,