refactor: move iterator trait to parent mod

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

mini-lsm-starter/src/iterators.rs

@@ -1,6 +1,19 @@
-pub mod impls;
 pub mod merge_iterator;
 pub mod two_merge_iterator;
 
+pub trait StorageIterator {
+    /// Get the current value.
+    fn value(&self) -> &[u8];
+
+    /// Get the current key.
+    fn key(&self) -> &[u8];
+
+    /// Check if the current iterator is valid.
+    fn is_valid(&self) -> bool;
+
+    /// Move to the next position.
+    fn next(&mut self) -> anyhow::Result<()>;
+}
+
 #[cfg(test)]
 mod tests;

mini-lsm-starter/src/iterators/impls.rs

@@ -1,15 +0,0 @@
-use anyhow::Result;
-
-pub trait StorageIterator {
-    /// Get the current value.
-    fn value(&self) -> &[u8];
-
-    /// Get the current key.
-    fn key(&self) -> &[u8];
-
-    /// Check if the current iterator is valid.
-    fn is_valid(&self) -> bool;
-
-    /// Move to the next position.
-    fn next(&mut self) -> Result<()>;
-}

mini-lsm-starter/src/iterators/merge_iterator.rs

@@ -6,7 +6,7 @@ use std::collections::BinaryHeap;
 
 use anyhow::Result;
 
-use super::impls::StorageIterator;
+use super::StorageIterator;
 
 struct HeapWrapper<I: StorageIterator>(pub usize, pub Box<I>);
 

mini-lsm-starter/src/iterators/two_merge_iterator.rs

@@ -3,7 +3,7 @@
 
 use anyhow::Result;
 
-use super::impls::StorageIterator;
+use super::StorageIterator;
 
 /// Merges two iterators of different types into one. If the two iterators have the same key, only
 /// produce the key once and prefer the entry from A.

mini-lsm-starter/src/lsm_iterator.rs

@@ -3,7 +3,7 @@
 
 use anyhow::Result;
 
-use crate::iterators::impls::StorageIterator;
+use crate::iterators::StorageIterator;
 
 pub struct LsmIterator {}
 

mini-lsm-starter/src/lsm_storage.rs

@@ -45,24 +45,32 @@ impl LsmStorage {
         })
     }
 
+    /// Get a key from the storage. In day 7, this can be further optimized by using a bloom filter.
     pub fn get(&self, key: &[u8]) -> Result<Option<Bytes>> {
         unimplemented!()
     }
 
+    /// Put a key-value pair into the storage by writing into the current memtable.
     pub fn put(&self, key: &[u8], value: &[u8]) -> Result<()> {
         assert!(!value.is_empty(), "value cannot be empty");
         assert!(!key.is_empty(), "key cannot be empty");
         unimplemented!()
     }
 
+    /// Remove a key from the storage by writing an empty value.
     pub fn delete(&self, _key: &[u8]) -> Result<()> {
         unimplemented!()
     }
 
+    /// Persist data to disk.
+    ///
+    /// In day 3: flush the current memtable to disk as L0 SST.
+    /// In day 6: call `fsync` on WAL.
     pub fn sync(&self) -> Result<()> {
         unimplemented!()
     }
 
+    /// Create an iterator over a range of keys.
     pub fn scan(
         &self,
         _lower: Bound<&[u8]>,

mini-lsm-starter/src/mem_table.rs

@@ -9,7 +9,7 @@ use bytes::Bytes;
 use crossbeam_skiplist::SkipMap;
 use ouroboros::self_referencing;
 
-use crate::iterators::impls::StorageIterator;
+use crate::iterators::StorageIterator;
 use crate::table::SsTableBuilder;
 
 /// A basic mem-table based on crossbeam-skiplist

mini-lsm-starter/src/table/iterator.rs

@@ -6,7 +6,7 @@ use std::sync::Arc;
 use anyhow::Result;
 
 use super::SsTable;
-use crate::iterators::impls::StorageIterator;
+use crate::iterators::StorageIterator;
 
 /// An iterator over the contents of an SSTable.
 pub struct SsTableIterator {}