Struct DatabaseOpenOptions

pub struct DatabaseOpenOptions<'e, 'n, KC, DC, C = DefaultComparator> { /* private fields */ }

Options and flags which can be used to configure how a Database is opened.

Examples

Opening a file to read:

use heed::types::*;
use heed::byteorder::BigEndian;

type BEI64 = I64<BigEndian>;

// Imagine you have an optional name
let conditional_name = Some("big-endian-iter");

let mut wtxn = env.write_txn()?;
let mut options = env.database_options().types::<BEI64, Unit>();
if let Some(name) = conditional_name {
   options.name(name);
}
let db = options.create(&mut wtxn)?;

db.put(&mut wtxn, &68, &())?;
db.put(&mut wtxn, &35, &())?;
db.put(&mut wtxn, &0, &())?;
db.put(&mut wtxn, &42, &())?;

wtxn.commit()?;

Implementations

impl<'e> DatabaseOpenOptions<'e, 'static, Unspecified, Unspecified>

pub fn new(env: &'e Env) -> Self

Create an options struct to open/create a database with specific flags.

impl<'e, 'n, KC, DC, C> DatabaseOpenOptions<'e, 'n, KC, DC, C>

pub fn types<NKC, NDC>(self) -> DatabaseOpenOptions<'e, 'n, NKC, NDC>

Change the type of the database.

The default types are Unspecified and require a call to Database::remap_types to use the Database.

pub fn key_comparator<NC>(self) -> DatabaseOpenOptions<'e, 'n, KC, DC, NC>

Change the customized key compare function of the database.

By default no customized compare function will be set when opening a database.

pub fn name(&mut self, name: &'n str) -> &mut Self

Change the name of the database.

By default the database is unnamed and there only is a single unnamed database.

pub fn flags(&mut self, flags: DatabaseFlags) -> &mut Self

Specify the set of flags used to open the database.

pub fn open(&self, rtxn: &RoTxn<'_>) -> Result<Option<Database<KC, DC, C>>>

where KC: 'static, DC: 'static, C: Comparator + 'static,

Opens a typed database that already exists in this environment.

If the database was previously opened in this program run, types will be checked.

Important Information

LMDB has an important restriction on the unnamed database when named ones are opened. The names of the named databases are stored as keys in the unnamed one and are immutable, and these keys can only be read and not written.

LMDB read-only access of existing database

In the case of accessing a database in a read-only manner from another process where you wrote, you might need to manually call RoTxn::commit to get metadata and the database handles opened and shared with the global Env handle.

If not done, you might raise Io(Os { code: 22, kind: InvalidInput, message: "Invalid argument" }) known as EINVAL.

pub fn create(&self, wtxn: &mut RwTxn<'_>) -> Result<Database<KC, DC, C>>

where KC: 'static, DC: 'static, C: Comparator + 'static,

Creates a typed database that can already exist in this environment.

If the database was previously opened in this program run, types will be checked.

Important Information

LMDB has an important restriction on the unnamed database when named ones are opened. The names of the named databases are stored as keys in the unnamed one and are immutable, and these keys can only be read and not written.

Trait Implementations

impl<KC, DC, C> Clone for DatabaseOpenOptions<'_, '_, KC, DC, C>

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'e, 'n, KC: Debug, DC: Debug, C: Debug> Debug for DatabaseOpenOptions<'e, 'n, KC, DC, C>

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

Formats the value using the given formatter.

impl<KC, DC, C> Copy for DatabaseOpenOptions<'_, '_, KC, DC, C>

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: 32 bytes