diff --git a/cozo-rocks/include/cozorocks.h b/cozo-rocks/include/cozorocks.h
index b8a37860..41008cc0 100644
--- a/cozo-rocks/include/cozorocks.h
+++ b/cozo-rocks/include/cozorocks.h
@@ -5,6 +5,7 @@
 #pragma once
 
 #include <memory>
+#include <mutex>
 #include "rust/cxx.h"
 
 #include "rocksdb/db.h"
@@ -234,6 +235,7 @@ inline unique_ptr <WriteBatchBridge> new_write_batch_raw() {
 struct DBBridge {
     mutable unique_ptr <DB> db;
     mutable unordered_map <string, shared_ptr<ColumnFamilyHandle>> handles;
+    mutable std::mutex handle_lock;
 
     DBBridge(DB *db_,
              unordered_map <string, shared_ptr<ColumnFamilyHandle>> &&handles_) : db(db_), handles(handles_) {}
@@ -313,13 +315,16 @@ struct DBBridge {
             write_status_impl(status, StatusCode::kMaxCode, StatusSubCode::kMaxSubCode, StatusSeverity::kSoftError, 2);
             return;
         }
+        handle_lock.lock();
         ColumnFamilyHandle *handle;
         auto s = db->CreateColumnFamily(options.inner, name, &handle);
         write_status(std::move(s), status);
         handles[name] = shared_ptr<ColumnFamilyHandle>(handle);
+        handle_lock.unlock();
     }
 
     inline void drop_column_family_raw(const string &name, BridgeStatus &status) const {
+        handle_lock.lock();
         auto cf_it = handles.find(name);
         if (cf_it != handles.end()) {
             auto s = db->DropColumnFamily(cf_it->second.get());
@@ -328,6 +333,7 @@ struct DBBridge {
         } else {
             write_status_impl(status, StatusCode::kMaxCode, StatusSubCode::kMaxSubCode, StatusSeverity::kSoftError, 3);
         }
+        handle_lock.unlock();
         // When should we call DestroyColumnFamilyHandle?
     }
 
diff --git a/cozo-rocks/src/lib.rs b/cozo-rocks/src/lib.rs
index 326c1d63..ade17ffc 100644
--- a/cozo-rocks/src/lib.rs
+++ b/cozo-rocks/src/lib.rs
@@ -131,7 +131,7 @@ mod ffi {
 use std::fmt::Formatter;
 use std::fmt::Debug;
 use std::path::Path;
-use cxx::{UniquePtr, SharedPtr, let_cxx_string};
+use cxx::{UniquePtr, SharedPtr, let_cxx_string, CxxString};
 pub use ffi::BridgeStatus;
 pub use ffi::StatusBridgeCode;
 pub use ffi::StatusCode;
@@ -288,15 +288,15 @@ impl IteratorImpl for IteratorBridge {
     }
 }
 
-fn get_path_bytes(path: &std::path::Path) -> &[u8] {
+fn get_path_bytes(path: &std::path::Path) -> Vec<u8> {
     #[cfg(unix)]
     {
         use std::os::unix::ffi::OsStrExt;
-        path.as_os_str().as_bytes()
+        path.as_os_str().as_bytes().to_vec()
     }
 
     #[cfg(not(unix))]
-    { path.to_string_lossy().to_string().as_bytes() }
+    { path.to_string_lossy().to_string().as_bytes().to_vec() }
 }
 
 impl Default for BridgeStatus {
@@ -313,6 +313,7 @@ impl Default for BridgeStatus {
 
 pub struct DB {
     inner: UniquePtr<DBBridge>,
+    pub path: Vec<u8>,
     pub options: Options,
     pub default_read_options: ReadOptions,
     pub default_write_options: WriteOptions,
@@ -322,35 +323,21 @@ unsafe impl Send for DB {}
 
 unsafe impl Sync for DB {}
 
-pub trait DBImpl {
-    fn open(options: Options, path: &Path) -> Result<DB>;
-    fn get_cf_handle(&self, name: impl AsRef<str>) -> Result<ColumnFamilyHandle>;
-    fn iterator(&self, cf: &ColumnFamilyHandle, options: Option<&ReadOptions>) -> DBIterator;
-    fn create_column_family(&self, name: impl AsRef<str>) -> Result<()>;
-    fn drop_column_family(&self, name: impl AsRef<str>) -> Result<()>;
-    fn all_cf_names(&self) -> Vec<String>;
-    fn get(&self, key: impl AsRef<[u8]>, cf: &ColumnFamilyHandle, options: Option<&ReadOptions>)
-           -> Result<Option<PinnableSlice>>;
-    fn put(&self, key: impl AsRef<[u8]>, val: impl AsRef<[u8]>, cf: &ColumnFamilyHandle, options: Option<&WriteOptions>)
-           -> Result<BridgeStatus>;
-    fn delete(&self, key: impl AsRef<[u8]>, cf: &ColumnFamilyHandle, options: Option<&WriteOptions>)
-              -> Result<BridgeStatus>;
-    fn write(&self, updates: WriteBatch, options: Option<&WriteOptions>) -> Result<BridgeStatus>;
-}
-
-impl DBImpl for DB {
-    fn open(options: Options, path: &Path) -> Result<DB> {
-        let_cxx_string!(path = get_path_bytes(path));
+impl DB {
+    pub fn open(options: Options, path: &Path) -> Result<DB> {
+        let path = get_path_bytes(path);
+        let_cxx_string!(cpp_path = path.clone());
         let mut status = BridgeStatus::default();
         let bridge = open_db_raw(
             &options,
-            &path,
+            &cpp_path,
             &mut status,
         );
 
         if status.code == StatusCode::kOk {
             Ok(DB {
                 inner: bridge,
+                path,
                 options,
                 default_read_options: ReadOptions::default(),
                 default_write_options: WriteOptions::default(),
@@ -360,7 +347,7 @@ impl DBImpl for DB {
         }
     }
 
-    fn get_cf_handle(&self, name: impl AsRef<str>) -> Result<ColumnFamilyHandle> {
+    pub fn get_cf_handle(&self, name: impl AsRef<str>) -> Result<ColumnFamilyHandle> {
         let_cxx_string!(name = name.as_ref());
         let ret = self.inner.get_cf_handle_raw(&name);
         if ret.is_null() {
@@ -376,11 +363,11 @@ impl DBImpl for DB {
     }
 
     #[inline]
-    fn iterator(&self, cf: &ColumnFamilyHandle, options: Option<&ReadOptions>) -> DBIterator {
+    pub fn iterator(&self, cf: &ColumnFamilyHandle, options: Option<&ReadOptions>) -> DBIterator {
         self.inner.iterator_raw(options.unwrap_or(&self.default_read_options), cf)
     }
 
-    fn create_column_family(&self, name: impl AsRef<str>) -> Result<()> {
+    pub fn create_column_family(&self, name: impl AsRef<str>) -> Result<()> {
         let_cxx_string!(name = name.as_ref());
         let mut status = BridgeStatus::default();
         self.inner.create_column_family_raw(&self.options, &name, &mut status);
@@ -391,7 +378,7 @@ impl DBImpl for DB {
         }
     }
 
-    fn drop_column_family(&self, name: impl AsRef<str>) -> Result<()> {
+    pub fn drop_column_family(&self, name: impl AsRef<str>) -> Result<()> {
         let_cxx_string!(name = name.as_ref());
         let mut status = BridgeStatus::default();
         self.inner.drop_column_family_raw(&name, &mut status);
@@ -402,12 +389,12 @@ impl DBImpl for DB {
         }
     }
 
-    fn all_cf_names(&self) -> Vec<String> {
+    pub fn all_cf_names(&self) -> Vec<String> {
         self.inner.get_column_family_names_raw().iter().map(|v| v.to_string_lossy().to_string()).collect()
     }
 
     #[inline]
-    fn get(&self, key: impl AsRef<[u8]>, cf: &ColumnFamilyHandle, options: Option<&ReadOptions>) -> Result<Option<PinnableSlice>> {
+    pub fn get(&self, key: impl AsRef<[u8]>, cf: &ColumnFamilyHandle, options: Option<&ReadOptions>) -> Result<Option<PinnableSlice>> {
         let mut status = BridgeStatus::default();
         let slice = self.inner.get_raw(options.unwrap_or(&self.default_read_options), cf, key.as_ref(), &mut status);
         match status.code {
@@ -418,7 +405,7 @@ impl DBImpl for DB {
     }
 
     #[inline]
-    fn put(&self, key: impl AsRef<[u8]>, val: impl AsRef<[u8]>, cf: &ColumnFamilyHandle, options: Option<&WriteOptions>) -> Result<BridgeStatus> {
+    pub fn put(&self, key: impl AsRef<[u8]>, val: impl AsRef<[u8]>, cf: &ColumnFamilyHandle, options: Option<&WriteOptions>) -> Result<BridgeStatus> {
         let mut status = BridgeStatus::default();
         self.inner.put_raw(options.unwrap_or(&self.default_write_options), cf,
                            key.as_ref(), val.as_ref(),
@@ -431,7 +418,7 @@ impl DBImpl for DB {
     }
 
     #[inline]
-    fn delete(&self, key: impl AsRef<[u8]>, cf: &ColumnFamilyHandle, options: Option<&WriteOptions>) -> Result<BridgeStatus> {
+    pub fn delete(&self, key: impl AsRef<[u8]>, cf: &ColumnFamilyHandle, options: Option<&WriteOptions>) -> Result<BridgeStatus> {
         let mut status = BridgeStatus::default();
         self.inner.delete_raw(options.unwrap_or(&self.default_write_options), cf,
                               key.as_ref(),
@@ -444,7 +431,7 @@ impl DBImpl for DB {
     }
 
     #[inline]
-    fn write(&self, mut updates: WriteBatch, options: Option<&WriteOptions>) -> Result<BridgeStatus> {
+    pub fn write(&self, mut updates: WriteBatch, options: Option<&WriteOptions>) -> Result<BridgeStatus> {
         let mut status = BridgeStatus::default();
         self.inner.write_raw(options.unwrap_or(&self.default_write_options),
                              updates.pin_mut(),
diff --git a/src/definition.rs b/src/definition.rs
index 8d45275f..ff6ae2a4 100644
--- a/src/definition.rs
+++ b/src/definition.rs
@@ -572,7 +572,7 @@ mod tests {
         let mut eval = EvaluatorWithStorage::new("_path_for_rocksdb_storagex".to_string()).unwrap();
         eval.build_table(parsed).unwrap();
         eval.restore_metadata().unwrap();
-        eval.storage.delete().unwrap();
+        eval.storage.delete_storage().unwrap();
         println!("{:#?}", eval.env.resolve("Person"));
         println!("{:#?}", eval.env.resolve("Friend"));
     }
diff --git a/src/error.rs b/src/error.rs
index 94235e0c..8db7e603 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -31,6 +31,9 @@ pub enum CozoError {
     #[error("Value required")]
     ValueRequired,
 
+    #[error("Incompatible value")]
+    IncompatibleValue,
+
     #[error("Wrong type")]
     WrongType,
 
diff --git a/src/mutation.rs b/src/mutation.rs
index 8be6d13c..9933355b 100644
--- a/src/mutation.rs
+++ b/src/mutation.rs
@@ -3,7 +3,7 @@ use pest::iterators::Pair;
 use crate::ast::{build_expr, Expr, ExprVisitor};
 use crate::definition::build_name_in_def;
 use crate::env::Env;
-use crate::error::CozoError::{UndefinedTable, ValueRequired};
+use crate::error::CozoError::{IncompatibleValue, UndefinedTable, ValueRequired};
 use crate::eval::Evaluator;
 use crate::storage::{RocksStorage};
 use crate::error::Result;
@@ -44,12 +44,13 @@ impl Evaluator<RocksStorage> {
             Expr::Const(v) => v,
             _ => return Err(ValueRequired)
         };
+        let val = val.get_list().ok_or(IncompatibleValue)?;
         println!("{:#?}", val);
         let coerced_values = self.coerce_table_values(&val, main_target);
         Ok(())
     }
 
-    fn coerce_table_values(&self, values: &Value, table: Option<&Structured>) -> BTreeMap<&Structured, Vec<Value>> {
+    fn coerce_table_values(&self, values: &[Value], default_table: Option<&Structured>) -> BTreeMap<&Structured, Vec<Value>> {
         todo!()
     }
 }
@@ -62,7 +63,7 @@ mod tests {
     use crate::ast::{Expr, ExprVisitor, parse_expr_from_str};
     use crate::eval::{BareEvaluator, EvaluatorWithStorage};
     use pest::Parser as PestParser;
-    use cozo_rocks::DBImpl;
+    use cozo_rocks::*;
     use crate::env::Env;
     use crate::typing::Structured;
 
@@ -80,7 +81,7 @@ mod tests {
 
         let data = fs::read_to_string("test_data/hr.json")?;
         let parsed = parse_expr_from_str(&data)?;
-        let mut ev = BareEvaluator::default();
+        let ev = BareEvaluator::default();
         let evaluated = ev.visit_expr(&parsed)?;
         let bound_value = match evaluated {
             Expr::Const(v) => v,
diff --git a/src/storage.rs b/src/storage.rs
index c201ff79..037a95d3 100644
--- a/src/storage.rs
+++ b/src/storage.rs
@@ -1,3 +1,4 @@
+use std::fs;
 use crate::error::{CozoError, Result};
 use cozo_rocks::*;
 use crate::value::{cozo_comparator_v1};
@@ -23,10 +24,13 @@ impl RocksStorage {
     }
 
     #[allow(unused_variables)]
-    pub fn delete(&mut self) -> Result<()> {
+    pub fn delete_storage(self) -> Result<()> {
         // unimplemented!()
         // drop(self.db.take());
         // DB::destroy(&make_options(), &self.path)?;
+        let path  = self.path.clone();
+        drop(self);
+        fs::remove_dir_all(path);
         Ok(())
     }