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use serde::{Deserialize, Serialize};
use garage_db as db;
use garage_util::data::*;
use crate::crdt::Crdt;
/// Trait for field used to partition data
pub trait PartitionKey {
/// Get the key used to partition
fn hash(&self) -> Hash;
}
impl PartitionKey for String {
fn hash(&self) -> Hash {
blake2sum(self.as_bytes())
}
}
/// Values of type FixedBytes32 are assumed to be random,
/// either a hash or a random UUID. This means we can use
/// them directly as an index into the hash table.
impl PartitionKey for FixedBytes32 {
fn hash(&self) -> Hash {
*self
}
}
/// Trait for field used to sort data
pub trait SortKey {
/// Get the key used to sort
fn sort_key(&self) -> &[u8];
}
impl SortKey for String {
fn sort_key(&self) -> &[u8] {
self.as_bytes()
}
}
impl SortKey for FixedBytes32 {
fn sort_key(&self) -> &[u8] {
self.as_slice()
}
}
/// Trait for an entry in a table. It must be sortable and partitionnable.
pub trait Entry<P: PartitionKey, S: SortKey>:
Crdt + PartialEq + Clone + Serialize + for<'de> Deserialize<'de> + Send + Sync
{
/// Get the key used to partition
fn partition_key(&self) -> &P;
/// Get the key used to sort
fn sort_key(&self) -> &S;
/// Is the entry a tombstone? Default implementation always return false
fn is_tombstone(&self) -> bool {
false
}
}
/// Trait for the schema used in a table
pub trait TableSchema: Send + Sync {
/// The name of the table in the database
const TABLE_NAME: &'static str;
/// The partition key used in that table
type P: PartitionKey + Clone + PartialEq + Serialize + for<'de> Deserialize<'de> + Send + Sync;
/// The sort key used int that table
type S: SortKey + Clone + Serialize + for<'de> Deserialize<'de> + Send + Sync;
/// They type for an entry in that table
type E: Entry<Self::P, Self::S>;
/// The type for a filter that can be applied to select entries
/// (e.g. filter out deleted entries)
type Filter: Clone + Serialize + for<'de> Deserialize<'de> + Send + Sync;
// Action to take if not able to decode current version:
// try loading from an older version
/// Try migrating an entry from an older version
fn try_migrate(_bytes: &[u8]) -> Option<Self::E> {
None
}
/// Actions triggered by data changing in a table. If such actions
/// include updates to the local database that should be applied
/// atomically with the item update itself, a db transaction is
/// provided on which these changes should be done.
/// This function can return a DB error but that's all.
fn updated(
&self,
_tx: &mut db::Transaction,
_old: Option<&Self::E>,
_new: Option<&Self::E>,
) -> db::Result<()> {
Ok(())
}
fn matches_filter(entry: &Self::E, filter: &Self::Filter) -> bool;
}
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