patch memtable and add ts for wal

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

mini-lsm-mvcc/src/lsm_iterator.rs

@@ -20,16 +20,24 @@ pub struct LsmIterator {
     inner: LsmIteratorInner,
     end_bound: Bound<Bytes>,
     is_valid: bool,
+    read_ts: u64,
+    prev_key: Vec<u8>,
 }
 
 impl LsmIterator {
-    pub(crate) fn new(iter: LsmIteratorInner, end_bound: Bound<Bytes>) -> Result<Self> {
+    pub(crate) fn new(
+        iter: LsmIteratorInner,
+        end_bound: Bound<Bytes>,
+        read_ts: u64,
+    ) -> Result<Self> {
         let mut iter = Self {
             is_valid: iter.is_valid(),
             inner: iter,
             end_bound,
+            read_ts,
+            prev_key: Vec::new(),
         };
-        iter.move_to_non_delete()?;
+        iter.move_to_key()?;
         Ok(iter)
     }
 
@@ -47,9 +55,31 @@ impl LsmIterator {
         Ok(())
     }
 
-    fn move_to_non_delete(&mut self) -> Result<()> {
-        while self.is_valid() && self.inner.value().is_empty() {
-            self.next_inner()?;
+    fn move_to_key(&mut self) -> Result<()> {
+        loop {
+            while self.inner.is_valid() && self.inner.key().key_ref() == self.prev_key {
+                self.next_inner()?;
+            }
+            if !self.inner.is_valid() {
+                break;
+            }
+            self.prev_key.clear();
+            self.prev_key.extend(self.inner.key().key_ref());
+            while self.inner.is_valid()
+                && self.inner.key().key_ref() == self.prev_key
+                && self.inner.key().ts() > self.read_ts
+            {
+                self.next_inner()?;
+            }
+            if !self.inner.is_valid() {
+                break;
+            }
+            if self.inner.key().key_ref() != self.prev_key {
+                continue;
+            }
+            if !self.inner.value().is_empty() {
+                break;
+            }
         }
         Ok(())
     }
@@ -72,7 +102,7 @@ impl StorageIterator for LsmIterator {
 
     fn next(&mut self) -> Result<()> {
         self.next_inner()?;
-        self.move_to_non_delete()?;
+        self.move_to_key()?;
         Ok(())
     }