mkleen commented on code in PR #22613:
URL: https://github.com/apache/datafusion/pull/22613#discussion_r3329859790
##########
datafusion/execution/src/cache/mod.rs:
##########
@@ -78,3 +82,83 @@ pub trait CacheAccessor<K, V>: Send + Sync {
/// Return the cache name.
fn name(&self) -> String;
}
+
+/// A managed cache with capacity, expiration, and introspection policies.
+///
+/// Keys must implement [`Key`] and values must implement [`Value`] so
+/// the implementation can account for heap usage when enforcing the cache
limit.
+///
+pub trait Cache<K: Key, V: Value>: CacheAccessor<K, V> {
+ /// Current memory budget, in bytes.
+ fn cache_limit(&self) -> usize;
+
+ /// Change the memory budget in bytes.
+ fn update_cache_limit(&self, limit: usize);
+
+ /// Time-to-live applied to newly inserted entries, or `None` if entries
+ /// never expire on their own.
+ fn cache_ttl(&self) -> Option<Duration>;
+
+ /// Change the TTL applied to subsequent inserts.
+ fn update_cache_ttl(&self, _ttl: Option<Duration>);
+
+ /// Invalidate every entry associated with `table_ref`.
+ fn drop_table_entries(
+ &self,
+ _table_ref: &Option<TableReference>,
+ ) -> datafusion_common::Result<()>;
+
+ /// Snapshot of all current entries with per-entry metadata (size, hits,
+ /// expiration) for diagnostics and observability.
+ fn list_entries(&self) -> HashMap<K, CacheEntryInfo<V>>;
+}
+
+/// Key type for entries stored in a [`Cache`].
+pub trait Key: Clone + Eq + Hash + Send + Sync + Debug {
+ /// Size of the key in bytes, used for cache memory accounting.
+ fn size(&self) -> usize;
+
+ /// Table this key is associated with, or `None` if the key is not
+ /// table-scoped.
+ fn table_ref(&self) -> Option<&TableReference>;
+}
+
+/// Value type for entries stored in a [`Cache`].
+pub trait Value: Clone + Send + Sync {
Review Comment:
OK.
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