Struct mmtkvdb::DbOptions

pub struct DbOptions<K: ?Sized, V: ?Sized, C, N> { /* private fields */ }

Options for opening a database

This struct follows the builder pattern. Start with DbOptions::new and pass completed builder by (shared) reference to Env::open_db or EnvRw::create_db to open or create a database.

Caveats / Safety

When opening an already existing database, all options must be compatible with the previously used options. It has be be ensured by the caller that this is true. Thus Env::open_db and EnvRw::create_db are marked as unsafe.

DbOptions::name has to be called last (after setting all other options). This is due to some restrictions regarding const fns. A compiler error will be reported if the methods are invoked in the wrong order.

Type arguments

The type arguments K, V, and C reflect the type used for keys and values, and whether duplicate keys are allowed (C being KeysUnique or KeysDuplicate), respectively.

The fourth type parameter determines if a name has been set (or the unnamed database has been selected), or if a name (or unnamed database) must be selected yet.

Example

use mmtkvdb::{self as kv, Env as _, Txn as _};
use tempfile::tempdir;
let location = tempdir().unwrap();
let env_builder = kv::EnvBuilder::new().dir(location.path()).max_dbs(1);
let mut env_rw = unsafe { env_builder.open_rw() }.unwrap();
let db_opts = kv::DbOptions::new()
    .key_type::<str>()
    .value_type::<i32>()
    .name("account_balance");
let db = unsafe { env_rw.create_db(&db_opts) }.unwrap();

Implementations

impl DbOptions<[u8], [u8], KeysUnique, ()>

pub const fn new() -> Self

Default options for database

impl<K: ?Sized, V: ?Sized, C> DbOptions<K, V, C, ()> where
    C: Constraint, 

pub const fn keys_unique(self) -> DbOptions<K, V, KeysUnique, ()>

Clear dupsort option (also clears reversedup option)

pub const fn keys_duplicate(self) -> DbOptions<K, V, KeysDuplicate, ()>

Set dupsort option

pub const fn key_type<T>(self) -> DbOptions<T, V, C, ()> where
    T: ?Sized + Storable, 

Set stored key type

pub const fn value_type<T>(self) -> DbOptions<K, T, C, ()> where
    T: ?Sized + Storable, 

Set stored value type

impl<K: ?Sized, V: ?Sized, C, N> DbOptions<K, V, C, N> where
    C: Constraint, 

pub const fn get_reversekey(&self) -> bool

Get reversekey option

pub const fn reversekey(self, flag: bool) -> Self

Set or clear reversekey option

pub fn unnamed(self) -> DbOptions<K, V, C, Option<CString>>

Use unnamed database

Should be used as last builder method because some other builder methods are not available anymore after calling this method.

pub fn name<T: Into<Vec<u8>>>(
    self,
    name: T
) -> DbOptions<K, V, C, Option<CString>>

Use named database (name must not contain a null byte)

Should be used as last builder method because some other builder methods are not available anymore after calling this method.

pub fn strip_name<T: Into<Vec<u8>>>(self) -> DbOptions<K, V, C, ()>

Remove name information

NOTE: This does not select the unnamed database. To select the unnamed database, use DbOptions::unnamed.

impl<K: ?Sized, V: ?Sized, C: Constraint, N> DbOptions<K, V, C, N>

pub fn has_duplicate_keys(&self) -> bool

Returns true if duplicate keys are allowed (i.e. is dupsort option set?)

impl<K: ?Sized, V: ?Sized, N> DbOptions<K, V, KeysDuplicate, N>

pub const fn get_reversedup(&self) -> bool

Get reversedup option

pub const fn reversedup(self, flag: bool) -> Self

Set or clear reversedup option

Trait Implementations

impl<K: Clone + ?Sized, V: Clone + ?Sized, C: Clone, N: Clone> Clone for DbOptions<K, V, C, N>

fn clone(&self) -> DbOptions<K, V, C, N>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<K: Debug + ?Sized, V: Debug + ?Sized, C: Debug, N: Debug> Debug for DbOptions<K, V, C, N>

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

Formats the value using the given formatter.