finish 3.5

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

mini-lsm-mvcc/src/mvcc/txn.rs

@@ -7,7 +7,7 @@ use std::{
     },
 };
 
-use anyhow::{bail, Result};
+use anyhow::Result;
 use bytes::Bytes;
 use crossbeam_skiplist::{map::Entry, SkipMap};
 use ouroboros::self_referencing;
@@ -20,8 +20,6 @@ use crate::{
     mem_table::map_bound,
 };
 
-use super::CommittedTxnData;
-
 pub struct Transaction {
     pub(crate) read_ts: u64,
     pub(crate) inner: Arc<LsmStorageInner>,
@@ -37,7 +35,11 @@ impl Transaction {
             panic!("cannot operate on committed txn!");
         }
         if let Some(entry) = self.local_storage.get(key) {
-            return Ok(Some(entry.value().clone()));
+            if entry.value().is_empty() {
+                return Ok(None);
+            } else {
+                return Ok(Some(entry.value().clone()));
+            }
         }
         self.inner.get_with_ts(key, self.read_ts)
     }
@@ -94,20 +96,6 @@ impl Transaction {
         self.committed
             .compare_exchange(false, true, Ordering::SeqCst, Ordering::SeqCst)
             .expect("cannot operate on committed txn!");
-        if let Some(guard) = &self.key_hashes {
-            let guard = guard.lock();
-            let (write_set, read_set) = &*guard;
-            if !write_set.is_empty() {
-                let committed_txns = self.inner.mvcc().committed_txns.lock();
-                for (_, txn_data) in committed_txns.range(self.read_ts..) {
-                    for key_hash in read_set {
-                        if txn_data.key_hashes.contains(key_hash) {
-                            bail!("serializable check failed");
-                        }
-                    }
-                }
-            }
-        }
         let batch = self
             .local_storage
             .iter()
@@ -119,32 +107,7 @@ impl Transaction {
                 }
             })
             .collect::<Vec<_>>();
-        let ts = self.inner.write_batch(&batch)?;
-        {
-            let mut committed_txns = self.inner.mvcc().committed_txns.lock();
-            let mut key_hashes = self.key_hashes.as_ref().unwrap().lock();
-            let (write_set, _) = &mut *key_hashes;
-
-            let old_data = committed_txns.insert(
-                ts,
-                CommittedTxnData {
-                    key_hashes: std::mem::take(write_set),
-                    read_ts: self.read_ts,
-                    commit_ts: ts,
-                },
-            );
-            assert!(old_data.is_none());
-
-            // remove unneeded txn data
-            let watermark = self.inner.mvcc().watermark();
-            while let Some(entry) = committed_txns.first_entry() {
-                if *entry.key() < watermark {
-                    entry.remove();
-                } else {
-                    break;
-                }
-            }
-        }
+        self.inner.write_batch(&batch)?;
         Ok(())
     }
 }