[−][src]Trait unqlite::Cursor

pub trait Cursor {
    fn first(&self) -> Option<Entry>;

    fn last(&self) -> Option<Entry>;

    fn seek<K: AsRef<[u8]>>(&self, key: K, pos: Direction) -> Option<Entry>;
}

Cursor iterator interfaces.

Cursors provide a mechanism by which you can iterate over the records in a database. Using cursors, you can seek, fetch, move, and delete database records.

To iterate over database records, from the first record to the last, simply call first to get the first valid cursor and loop to the next:

use unqlite::{UnQLite, Cursor};
let unqlite = UnQLite::create_temp();
let mut entry = unqlite.first();

loop {
    if entry.is_none() { break; }

    let record = entry.expect("valid entry");
    println!("{:?}", record.key_value());
    entry = record.next();
}

To iterate over database records, from the last record to the first, just replace first as last, call prev instead of next() on entry.

You can also use cursors to search for records and start the iteration process from there. To do that, start from seek method.

To retrieve record key/value from a valid cursor, just use like:

ⓘThis example is not tested
let entry = ...; // Get the cursor entry
let key = entry.key();                   // Key only
let value = entry.value();               // Value only
let (key, value) = entry.key_value();    // Key-Value pair

To delete a record from the database using the cursor interface, simply point to the target record using seek and call delete on the Entry object.

A rusty Iterator style would perform in a short time.

Required methods

fn first(&self) -> Option<Entry>

Returns the first entry.

fn last(&self) -> Option<Entry>

Retruns the last entry.

fn seek<K: AsRef<[u8]>>(&self, key: K, pos: Direction) -> Option<Entry>

Seek an entry by key.

The pos Direction options:

  • Exact: If the record exists, the cursor is left pointing to it, otherwise return None.
  • Le: The cursor is left pointing to the largest key in the database that is smaller than key, If the database contains no keys smaller than key, it returns None.
  • Ge: Oppsite to Le, it returns the smallest Entry in the database that is larger than key.If the database contains no keys smaller than key, return None.
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Implementors

impl Cursor for UnQLite[src]

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