Key Value Storage

Verisense has a full set of API on KV storage. Let's look at it.

APIs

put

Put a value into database via a key.

pub fn put(key: impl AsRef<[u8]>, value: impl AsRef<[u8]>) -> CallResult<()>

Example:

use vrs_core_sdk::{get, post, storage};

#[post]
pub fn add_user(mut u: User) -> Result<(), String> {
    let key = b"user:001";
    let val: Vec<u8> = u.encode();     
    storage::put(&key, &val).map_err(|e| e.to_string())?;

    Ok(())
}

Note: storage::put() can only be used in the function decorated by #[post].

del

Delete a value from database via a key.

pub fn del(key: impl AsRef<[u8]>) -> CallResult<()>

Example:

use vrs_core_sdk::{get, post, storage};

#[post]
pub fn delete_user() -> Result<(), String> {
    let key = b"user:001";

    storage::del(&key).map_err(|e| e.to_string())?;

    Ok(())
}

Note: storage::del() can only be used in the function decorated by #[post].

get

Get a value from database via a key.

pub fn get(key: impl AsRef<[u8]>) -> CallResult<Option<Vec<u8>>> {

Example:

#[get]
pub fn get_user() -> Result<Option<User>, String> {
    let key = b"user:001";
    let r = storage::get(&key).map_err(|e| e.to_string())?;
    let instance = r.map(|d| User::decode(&mut &d[..]).unwrap());
    Ok(instance)
}

get_range

Get a batch of entries from the database with "start_key" and direction, the limit maximum is 1000

pub fn get_range(
    start_key: impl AsRef<[u8]>,
    direction: Direction,
    limit: usize,
) -> CallResult<Vec<(Vec<u8>, Vec<u8>)>>

Example:

#[get]
pub fn get_user_range() -> Result<(), String>  {
    let prefix_key = b"user:";
    let r = storage::get_range(&key, Direction::Forward, 100).map_err(|e| e.to_string())?;
    ...
}

delete_range

Removes the database entries in the range [start_key, end_key)

pub fn delete_range(start_key: impl AsRef<[u8]>, end_key: impl AsRef<[u8]>) -> CallResult<()>

Example:

#[post]
pub fn delete_user_range() -> Result<(), String>  {
    let start_key = b"user:001";
    let end_key = b"user:100";
    let r = storage::delete_range(&start_key, &end_key).map_err(|e| e.to_string())?;
    ...
}

Note: storage::delete_range() can only be used in the function decorated by #[post].

Search a value with a key prefix and direction.

pub fn search(
    key_prefix: impl AsRef<[u8]>,
    direction: Direction,
) -> CallResult<Option<(Vec<u8>, Vec<u8>)>>

Example:

use vrs_core_sdk::storage::Direction;

pub fn search_blog_id() {
   let key = [&b"blog:"[..], &0u64.to_be_bytes()[..]].concat();
   let first_blog = storage::search(&key, Direction::Forward).unwrap();
   let key = [&b"blog:"[..], &u64::MAX.to_be_bytes()[..]].concat();
   let last_blog = storage::search(&key, Direction::Reverse).unwrap();
   assert!(first_blog.is_some());
   assert!(last_blog.is_some());
}