fix(hot): MemKvRwTx read cursor now sees queued writes (#32)

`HotKvRead for MemKvRwTx` previously returned `MemKvCursor` which only
sees committed data. This caused read cursors on write transactions to
miss pending writes, creating an inconsistency with `raw_get` which
already checked queued ops. Change `Traverse` type to `MemKvCursorMut`
which merges committed data with queued writes.

Also fix a pre-existing bug in `MemKvCursorMut::last_of_k1` where the
k1 comparison used full MAX_KEY_SIZE bytes against the shorter encoded
key, causing it to always return None.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: prestwich

Cargo.toml

@@ -3,7 +3,7 @@ members = ["crates/*"]
 resolver = "2"
 
 [workspace.package]
-version = "0.6.1"
+version = "0.6.2"
 edition = "2024"
 rust-version = "1.92"
 authors = ["init4"]
@@ -35,13 +35,13 @@ incremental = false
 
 [workspace.dependencies]
 # internal
-signet-hot = { version = "0.6.1", path = "./crates/hot" }
-signet-hot-mdbx = { version = "0.6.1", path = "./crates/hot-mdbx" }
-signet-cold = { version = "0.6.1", path = "./crates/cold" }
-signet-cold-mdbx = { version = "0.6.1", path = "./crates/cold-mdbx" }
-signet-cold-sql = { version = "0.6.1", path = "./crates/cold-sql" }
-signet-storage = { version = "0.6.1", path = "./crates/storage" }
-signet-storage-types = { version = "0.6.1", path = "./crates/types" }
+signet-hot = { version = "0.6.2", path = "./crates/hot" }
+signet-hot-mdbx = { version = "0.6.2", path = "./crates/hot-mdbx" }
+signet-cold = { version = "0.6.2", path = "./crates/cold" }
+signet-cold-mdbx = { version = "0.6.2", path = "./crates/cold-mdbx" }
+signet-cold-sql = { version = "0.6.2", path = "./crates/cold-sql" }
+signet-storage = { version = "0.6.2", path = "./crates/storage" }
+signet-storage-types = { version = "0.6.2", path = "./crates/types" }
 
 # External, in-house
 signet-libmdbx = { version = "0.8.0" }

crates/hot/src/mem.rs

@@ -1057,7 +1057,9 @@ impl<'a> DualKeyTraverse<MemKvError> for MemKvCursorMut<'a> {
             return Ok(None);
         };
         let (found_k1, found_k2) = MemKv::split_dual_key(&found_key);
-        if found_k1.as_ref() != key1 {
+        // Compare only the relevant prefix of found_k1 with key1
+        // found_k1 is MAX_KEY_SIZE bytes, key1 may be shorter
+        if &found_k1.as_ref()[..key1.len()] != key1 {
             self.clear_current_key();
             return Ok(None);
         }
@@ -1265,11 +1267,10 @@ impl MemKvRoTx {
 impl HotKvRead for MemKvRwTx {
     type Error = MemKvError;
 
-    type Traverse<'a> = MemKvCursor<'a>;
+    type Traverse<'a> = MemKvCursorMut<'a>;
 
     fn raw_traverse<'a>(&'a self, table: &str) -> Result<Self::Traverse<'a>, Self::Error> {
-        let table_data = self.guard.get(table).unwrap_or(&EMPTY_TABLE);
-        Ok(MemKvCursor::new(table_data))
+        self.cursor_mut(table)
     }
 
     fn raw_get<'a>(
@@ -1318,14 +1319,10 @@ impl HotKvRead for MemKvRwTx {
 }
 
 impl MemKvRwTx {
-    /// Get a read-only cursor for the specified table
-    /// Note: This cursor will NOT see pending writes from this transaction
-    pub fn cursor<'a>(&'a self, table: &str) -> Result<MemKvCursor<'a>, MemKvError> {
-        if let Some(table_data) = self.guard.get(table) {
-            Ok(MemKvCursor::new(table_data))
-        } else {
-            Err(MemKvError::HotKv(HotKvError::Inner(format!("Table '{}' not found", table).into())))
-        }
+    /// Get a cursor for the specified table that sees both committed data
+    /// and pending writes from this transaction.
+    pub fn cursor<'a>(&'a self, table: &str) -> Result<MemKvCursorMut<'a>, MemKvError> {
+        self.cursor_mut(table)
     }
 
     /// Get a mutable cursor for the specified table