From b590b353eb2a49aae8ae15f06fd06107793da400 Mon Sep 17 00:00:00 2001
From: Pekka Enberg <penberg@iki.fi>
Date: Wed, 24 Sep 2025 10:36:56 +0300
Subject: [PATCH] core/mvcc: Wrap Transaction::database_header with RwLock

---
 core/mvcc/database/mod.rs   | 15 +++++++--------
 core/mvcc/database/tests.rs |  6 +++---
 2 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/core/mvcc/database/mod.rs b/core/mvcc/database/mod.rs
index 3621b5c97..95b36beb9 100644
--- a/core/mvcc/database/mod.rs
+++ b/core/mvcc/database/mod.rs
@@ -19,7 +19,6 @@ use crate::Result;
 use crate::{Connection, Pager};
 use crossbeam_skiplist::{SkipMap, SkipSet};
 use parking_lot::RwLock;
-use std::cell::RefCell;
 use std::collections::HashMap;
 use std::collections::HashSet;
 use std::fmt::Debug;
@@ -118,7 +117,7 @@ pub struct Transaction {
     /// The transaction read set.
     read_set: SkipSet<RowID>,
     /// The transaction header.
-    header: RefCell<DatabaseHeader>,
+    header: RwLock<DatabaseHeader>,
 }
 
 impl Transaction {
@@ -129,7 +128,7 @@ impl Transaction {
             begin_ts,
             write_set: SkipSet::new(),
             read_set: SkipSet::new(),
-            header: RefCell::new(header),
+            header: RwLock::new(header),
         }
     }
 
@@ -770,7 +769,7 @@ impl<Clock: LogicalClock> StateTransition for CommitStateMachine<Clock> {
                         // FIXME: hack for now to keep database header updated for pager commit
                         let tx = mvcc_store.txs.get(&self.tx_id).unwrap();
                         let tx_unlocked = tx.value();
-                        self.header.write().replace(*tx_unlocked.header.borrow());
+                        self.header.write().replace(*tx_unlocked.header.read());
                         self.commit_coordinator.pager_commit_lock.unlock();
                         // TODO: here mark we are ready for a batch
                         self.state = CommitState::Commit { end_ts: *end_ts };
@@ -874,7 +873,7 @@ impl<Clock: LogicalClock> StateTransition for CommitStateMachine<Clock> {
                 }
                 let tx = mvcc_store.txs.get(&self.tx_id).unwrap();
                 let tx_unlocked = tx.value();
-                self.header.write().replace(*tx_unlocked.header.borrow());
+                self.header.write().replace(*tx_unlocked.header.read());
                 tracing::trace!("end_commit_logical_log(tx_id={})", self.tx_id);
                 self.commit_coordinator.pager_commit_lock.unlock();
                 self.state = CommitState::CommitEnd { end_ts: *end_ts };
@@ -1502,7 +1501,7 @@ impl<Clock: LogicalClock> MvStore<Clock> {
             .get(tx_id)
             .expect("transaction not found when trying to get header");
         let header = tx.value();
-        let header = header.header.borrow();
+        let header = header.header.read();
         tracing::debug!("get_transaction_database_header read: header={:?}", header);
         *header
     }
@@ -1514,7 +1513,7 @@ impl<Clock: LogicalClock> MvStore<Clock> {
         if let Some(tx_id) = tx_id {
             let tx = self.txs.get(tx_id).unwrap();
             let header = tx.value();
-            let header = header.header.borrow();
+            let header = header.header.read();
             tracing::debug!("with_header read: header={:?}", header);
             Ok(f(&header))
         } else {
@@ -1531,7 +1530,7 @@ impl<Clock: LogicalClock> MvStore<Clock> {
         if let Some(tx_id) = tx_id {
             let tx = self.txs.get(tx_id).unwrap();
             let header = tx.value();
-            let mut header = header.header.borrow_mut();
+            let mut header = header.header.write();
             tracing::debug!("with_header_mut read: header={:?}", header);
             Ok(f(&mut header))
         } else {
diff --git a/core/mvcc/database/tests.rs b/core/mvcc/database/tests.rs
index cc693abdf..ff35ba9ab 100644
--- a/core/mvcc/database/tests.rs
+++ b/core/mvcc/database/tests.rs
@@ -2,7 +2,7 @@ use super::*;
 use crate::io::PlatformIO;
 use crate::mvcc::clock::LocalClock;
 use crate::storage::sqlite3_ondisk::DatabaseHeader;
-use std::cell::RefCell;
+use parking_lot::RwLock;
 
 pub(crate) struct MvccTestDbNoConn {
     pub(crate) db: Option<Arc<Database>>,
@@ -1041,7 +1041,7 @@ fn new_tx(tx_id: TxID, begin_ts: u64, state: TransactionState) -> Transaction {
         begin_ts,
         write_set: SkipSet::new(),
         read_set: SkipSet::new(),
-        header: RefCell::new(DatabaseHeader::default()),
+        header: RwLock::new(DatabaseHeader::default()),
     }
 }
 
@@ -1453,7 +1453,7 @@ fn transaction_display() {
         begin_ts,
         write_set,
         read_set,
-        header: RefCell::new(DatabaseHeader::default()),
+        header: RwLock::new(DatabaseHeader::default()),
     };
 
     let expected = "{ state: Preparing, id: 42, begin_ts: 20250914, write_set: [RowID { table_id: 1, row_id: 11 }, RowID { table_id: 1, row_id: 13 }], read_set: [RowID { table_id: 2, row_id: 17 }, RowID { table_id: 2, row_id: 19 }] }";