perf(encoding): use estimate size to reserve memory in row encoding (r…

…isingwavelabs#8909)

Co-authored-by: stonepage <40830455+st1page@users.noreply.github.com>

src/common/src/row/mod.rs

@@ -78,15 +78,23 @@ pub trait Row: Sized + std::fmt::Debug + PartialEq + Eq {
     /// Serializes the row with value encoding and returns the bytes.
     #[inline]
     fn value_serialize(&self) -> Vec<u8> {
-        let mut buf = Vec::with_capacity(self.len()); // each datum is at least 1 byte
+        let estimate_size = self
+            .iter()
+            .map(value_encoding::estimate_serialize_datum_size)
+            .sum();
+        let mut buf = Vec::with_capacity(estimate_size);
         self.value_serialize_into(&mut buf);
         buf
     }
 
     /// Serializes the row with value encoding and returns the bytes.
     #[inline]
     fn value_serialize_bytes(&self) -> Bytes {
-        let mut buf = BytesMut::with_capacity(self.len()); // each datum is at least 1 byte
+        let estimate_size = self
+            .iter()
+            .map(value_encoding::estimate_serialize_datum_size)
+            .sum();
+        let mut buf = BytesMut::with_capacity(estimate_size);
         self.value_serialize_into(&mut buf);
         buf.freeze()
     }