New state pruning algorithm

beacon_node/store/src/lib.rs

@@ -75,6 +75,15 @@ pub trait KeyValueStore<E: EthSpec>: Sync + Send + Sized + 'static {
 
     /// Compact the database, freeing space used by deleted items.
     fn compact(&self) -> Result<(), Error>;
+
+    /// Iterate through all values in a particular column.
+    fn iter_column<'a>(
+        &'a self,
+        _column: DBColumn,
+    ) -> Box<dyn Iterator<Item = Result<(Hash256, Vec<u8>), Error>> + 'a> {
+        // Default impl for non LevelDB databases
+        Box::new(std::iter::empty())
+    }
 }
 
 pub fn get_key_for_col(column: &str, key: &[u8]) -> Vec<u8> {
@@ -144,6 +153,7 @@ pub enum StoreOp<'a, E: EthSpec> {
     DeleteStateTemporaryFlag(Hash256),
     DeleteBlock(Hash256),
     DeleteState(Hash256, Option<Slot>),
+    KeyValueOp(KeyValueStoreOp),
 }
 
 /// A unique column identifier.