Trait KeyValueDB 

pub trait KeyValueDB:
    Sync
    + Send
    + Clone
    + 'static {
    // Required methods
    fn get<'a>(
        &'a self,
        col: u32,
        key: &'a [u8],
    ) -> Pin<Box<dyn Future<Output = Result<Option<Vec<u8>>, Error>> + Send + 'a>>;
    fn delete<'a>(
        &'a self,
        col: u32,
        key: &'a [u8],
    ) -> Pin<Box<dyn Future<Output = Result<Option<Vec<u8>>, Error>> + Send + 'a>>;
    fn write(
        &self,
        transaction: DBTransaction,
    ) -> Pin<Box<dyn Future<Output = Result<(), DBTransactionError>> + Send + '_>>;
    fn iter<'a, T, C, F>(
        &'a self,
        col: u32,
        prefix: Option<&'a [u8]>,
        context: C,
        f: F,
    ) -> Pin<Box<dyn Future<Output = Result<(C, Option<T>), Error>> + Send + 'a>>
       where T: Send + 'static,
             C: Send + 'static,
             F: FnMut(&mut C, (&Vec<u8>, &Vec<u8>)) -> Result<Option<T>, Error> + Send + Sync + 'static;
    fn iter_keys<'a, T, C, F>(
        &'a self,
        col: u32,
        prefix: Option<&'a [u8]>,
        context: C,
        f: F,
    ) -> Pin<Box<dyn Future<Output = Result<(C, Option<T>), Error>> + Send + 'a>>
       where T: Send + 'static,
             C: Send + 'static,
             F: FnMut(&mut C, &Vec<u8>) -> Result<Option<T>, Error> + Send + Sync + 'static;
    fn num_columns(&self) -> Result<u32, Error>;
    fn num_keys(
        &self,
        col: u32,
    ) -> Pin<Box<dyn Future<Output = Result<u64, Error>> + Send + '_>>;

    // Provided methods
    fn transaction(&self) -> DBTransaction { ... }
    fn io_stats(&self, _kind: Kind) -> IoStats { ... }
    fn has_key<'a>(
        &'a self,
        col: u32,
        key: &'a [u8],
    ) -> Pin<Box<dyn Future<Output = Result<bool, Error>> + Send + 'a>> { ... }
    fn has_prefix<'a>(
        &'a self,
        col: u32,
        prefix: &'a [u8],
    ) -> Pin<Box<dyn Future<Output = Result<bool, Error>> + Send + 'a>> { ... }
    fn first_with_prefix<'a>(
        &'a self,
        col: u32,
        prefix: &'a [u8],
    ) -> Pin<Box<dyn Future<Output = Result<Option<(Vec<u8>, Vec<u8>)>, Error>> + Send + 'a>> { ... }
    fn cleanup(
        &self,
    ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send + '_>> { ... }
}

Generic key-value database.

The KeyValueDB deals with “column families”, which can be thought of as distinct stores within a database. Keys written in one column family will not be accessible from any other. The number of column families must be specified at initialization, with a differing interface for each database.

The API laid out here, along with the Sync bound implies interior synchronization for implementation. Clone is here so we can pass an owned self to async functions, requiring interior locked mutability.

Required Methods

fn get<'a>( &'a self, col: u32, key: &'a [u8], ) -> Pin<Box<dyn Future<Output = Result<Option<Vec<u8>>, Error>> + Send + 'a>>

Get a value by key.

fn delete<'a>( &'a self, col: u32, key: &'a [u8], ) -> Pin<Box<dyn Future<Output = Result<Option<Vec<u8>>, Error>> + Send + 'a>>

Remove a value by key, returning the old value

fn write( &self, transaction: DBTransaction, ) -> Pin<Box<dyn Future<Output = Result<(), DBTransactionError>> + Send + '_>>

Write a transaction of changes to the backing store.

fn iter<'a, T, C, F>( &'a self, col: u32, prefix: Option<&'a [u8]>, context: C, f: F, ) -> Pin<Box<dyn Future<Output = Result<(C, Option<T>), Error>> + Send + 'a>>

where T: Send + 'static, C: Send + 'static, F: FnMut(&mut C, (&Vec<u8>, &Vec<u8>)) -> Result<Option<T>, Error> + Send + Sync + 'static,

Iterate over the data for a given column. Return all key/value pairs, optionally where the key starts with the given prefix. Iterator closure returns true for more items, false to stop iteration.

fn iter_keys<'a, T, C, F>( &'a self, col: u32, prefix: Option<&'a [u8]>, context: C, f: F, ) -> Pin<Box<dyn Future<Output = Result<(C, Option<T>), Error>> + Send + 'a>>

where T: Send + 'static, C: Send + 'static, F: FnMut(&mut C, &Vec<u8>) -> Result<Option<T>, Error> + Send + Sync + 'static,

Iterate over the data for a given column. Return all keys, optionally where the key starts with the given prefix. Iterator closure returns true for more items, false to stop iteration.

fn num_columns(&self) -> Result<u32, Error>

The number of column families in the db.

fn num_keys( &self, col: u32, ) -> Pin<Box<dyn Future<Output = Result<u64, Error>> + Send + '_>>

The number of keys in a column (estimated).

Provided Methods

fn transaction(&self) -> DBTransaction

Helper to create a new transaction.

fn io_stats(&self, _kind: Kind) -> IoStats

Query statistics.

Not all keyvaluedb implementations are able or expected to implement this, so by default, empty statistics is returned. Also, not all keyvaluedb implementation can return every statistic or configured to do so (some statistics gathering may impede the performance and might be off by default).

fn has_key<'a>( &'a self, col: u32, key: &'a [u8], ) -> Pin<Box<dyn Future<Output = Result<bool, Error>> + Send + 'a>>

Check for the existence of a value by key.

fn has_prefix<'a>( &'a self, col: u32, prefix: &'a [u8], ) -> Pin<Box<dyn Future<Output = Result<bool, Error>> + Send + 'a>>

Check for the existence of a value by prefix.

fn first_with_prefix<'a>( &'a self, col: u32, prefix: &'a [u8], ) -> Pin<Box<dyn Future<Output = Result<Option<(Vec<u8>, Vec<u8>)>, Error>> + Send + 'a>>

Get the first value matching the given prefix.

fn cleanup( &self, ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send + '_>>

Cleanup/Vacuum database

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl KeyValueDB for InMemory

fn delete<'a>( &'a self, col: u32, key: &'a [u8], ) -> Pin<Box<dyn Future<Output = Result<Option<Vec<u8>>, Error>> + Send + 'a>>

Remove a value by key, returning the old value

fn get<'a>( &'a self, col: u32, key: &'a [u8], ) -> Pin<Box<dyn Future<Output = Result<Option<Vec<u8>>, Error>> + Send + 'a>>

fn write( &self, transaction: DBTransaction, ) -> Pin<Box<dyn Future<Output = Result<(), DBTransactionError>> + Send + '_>>

fn iter<'a, T, C, F>( &'a self, col: u32, prefix: Option<&'a [u8]>, context: C, f: F, ) -> Pin<Box<dyn Future<Output = Result<(C, Option<T>), Error>> + Send + 'a>>

where T: Send + 'static, C: Send + 'static, F: FnMut(&mut C, (&Vec<u8>, &Vec<u8>)) -> Result<Option<T>, Error> + Send + Sync + 'static,

fn iter_keys<'a, T, C, F>( &'a self, col: u32, prefix: Option<&'a [u8]>, context: C, f: F, ) -> Pin<Box<dyn Future<Output = Result<(C, Option<T>), Error>> + Send + 'a>>

where T: Send + 'static, C: Send + 'static, F: FnMut(&mut C, &Vec<u8>) -> Result<Option<T>, Error> + Send + Sync + 'static,

fn num_columns(&self) -> Result<u32, Error>

fn num_keys( &self, col: u32, ) -> Pin<Box<dyn Future<Output = Result<u64, Error>> + Send + '_>>

Implementors

impl KeyValueDB for Database