Struct Database

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pub struct Database<E>where
    E: DatabaseKind,
{ /* private fields */ }

Expand description

Supports multiple tables, all residing in the same shared-memory map.

Implementations§

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impl<E> Database<E>
where E: DatabaseKind,

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pub fn open(path: impl AsRef<Path>) -> Result<Database<E>>

Open a database.

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pub fn open_with_options( path: impl AsRef<Path>, options: DatabaseOptions, ) -> Result<Database<E>>

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pub fn ptr(&self) -> DbPtr

Returns a raw pointer to the underlying MDBX database.

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

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

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

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

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

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

Flush the database data buffers to disk.

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

Retrieves statistics about this database.

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

Retrieves info about this database.

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

Retrieves the total number of pages on the freelist.

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

let dir = tempfile::tempdir().unwrap();
let db = Database::<NoWriteMap>::open(&dir).unwrap();
let info = db.info().unwrap();
let stat = db.stat().unwrap();
let freelist = db.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 table 0 in each database, and the freelist count is stored at the beginning of the value as 32-bit integer in the native byte order.
It will create a read transaction to traverse the freelist table.