diff --git a/mini-lsm-starter/src/debug.rs b/mini-lsm-starter/src/debug.rs
new file mode 100644
index 00000000..76702de8
--- /dev/null
+++ b/mini-lsm-starter/src/debug.rs
@@ -0,0 +1,17 @@
+use crate::lsm_storage::MiniLsm;
+
+impl MiniLsm {
+    pub fn dump_structure(&self) {
+        let snapshot = self.inner.state.read();
+        if !snapshot.l0_sstables.is_empty() {
+            println!(
+                "L0 ({}): {:?}",
+                snapshot.l0_sstables.len(),
+                snapshot.l0_sstables,
+            );
+        }
+        for (level, files) in &snapshot.levels {
+            println!("L{level} ({}): {:?}", files.len(), files);
+        }
+    }
+}
diff --git a/mini-lsm-starter/src/lib.rs b/mini-lsm-starter/src/lib.rs
index ac8e8ce6..ebfb02af 100644
--- a/mini-lsm-starter/src/lib.rs
+++ b/mini-lsm-starter/src/lib.rs
@@ -1,5 +1,6 @@
 pub mod block;
 pub mod compact;
+pub mod debug;
 pub mod iterators;
 pub mod lsm_iterator;
 pub mod lsm_storage;
diff --git a/mini-lsm-starter/src/table.rs b/mini-lsm-starter/src/table.rs
index 9dcaa3ac..8173a87a 100644
--- a/mini-lsm-starter/src/table.rs
+++ b/mini-lsm-starter/src/table.rs
@@ -20,8 +20,10 @@ use crate::lsm_storage::BlockCache;
 pub struct BlockMeta {
     /// Offset of this data block.
     pub offset: usize,
-    /// The first key of the data block, mainly used for index purpose.
+    /// The first key of the data block.
     pub first_key: Bytes,
+    /// The last key of the data block.
+    pub last_key: Bytes,
 }
 
 impl BlockMeta {
@@ -138,7 +140,23 @@ impl SsTable {
 
     /// Get number of data blocks.
     pub fn num_of_blocks(&self) -> usize {
-        unimplemented!()
+        self.block_metas.len()
+    }
+
+    pub fn first_key(&self) -> &Bytes {
+        &self.first_key
+    }
+
+    pub fn last_key(&self) -> &Bytes {
+        &self.last_key
+    }
+
+    pub fn table_size(&self) -> u64 {
+        self.file.1
+    }
+
+    pub fn sst_id(&self) -> usize {
+        self.id
     }
 }
 
diff --git a/mini-lsm/src/block.rs b/mini-lsm/src/block.rs
index 65935ed1..fe4e0356 100644
--- a/mini-lsm/src/block.rs
+++ b/mini-lsm/src/block.rs
@@ -5,7 +5,7 @@ pub use builder::BlockBuilder;
 use bytes::{Buf, BufMut, Bytes};
 pub use iterator::BlockIterator;
 
-pub const SIZEOF_U16: usize = std::mem::size_of::<u16>();
+pub(crate) const SIZEOF_U16: usize = std::mem::size_of::<u16>();
 
 /// A block is the smallest unit of read and caching in LSM tree. It is a collection of sorted
 /// key-value pairs.