finish serializable check

Signed-off-by: Alex Chi <iskyzh@gmail.com>

mini-lsm-mvcc/src/mvcc.rs

@@ -14,8 +14,10 @@ use crate::lsm_storage::LsmStorageInner;
 use self::{txn::Transaction, watermark::Watermark};
 
 pub(crate) struct CommittedTxnData {
-    pub(crate) key_hashes: Vec<u32>,
+    pub(crate) key_hashes: HashSet<u32>,
+    #[allow(dead_code)]
     pub(crate) read_ts: u64,
+    #[allow(dead_code)]
     pub(crate) commit_ts: u64,
 }
 
@@ -58,7 +60,7 @@ impl LsmMvccInner {
             local_storage: Arc::new(SkipMap::new()),
             committed: Arc::new(AtomicBool::new(false)),
             key_hashes: if serializable {
-                Some(Mutex::new(HashSet::new()))
+                Some(Mutex::new((HashSet::new(), HashSet::new())))
             } else {
                 None
             },