From 2fd4407a038b68073990313bea65ca4326f52029 Mon Sep 17 00:00:00 2001
From: Pere Diaz Bou <pere-altea@hotmail.com>
Date: Wed, 5 Nov 2025 13:07:17 +0100
Subject: [PATCH] core/execute: map negative root page to positive if we can

---
 core/mvcc/database/mod.rs |  9 +++++++++
 core/vdbe/execute.rs      | 24 +++++++++++++++++++-----
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/core/mvcc/database/mod.rs b/core/mvcc/database/mod.rs
index cb911db19..77e6412b5 100644
--- a/core/mvcc/database/mod.rs
+++ b/core/mvcc/database/mod.rs
@@ -1925,6 +1925,15 @@ impl<Clock: LogicalClock> MvStore<Clock> {
     pub fn checkpoint_threshold(&self) -> i64 {
         self.storage.checkpoint_threshold()
     }
+
+    pub fn get_real_table_id(&self, table_id: i64) -> i64 {
+        let entry = self.table_id_to_rootpage.get(&MVTableId::from(table_id));
+        if let Some(entry) = entry {
+            entry.value().map_or(table_id, |value| value as i64)
+        } else {
+            table_id
+        }
+    }
 }
 
 /// A write-write conflict happens when transaction T_current attempts to update a
diff --git a/core/vdbe/execute.rs b/core/vdbe/execute.rs
index e61aa7040..2c2abbc77 100644
--- a/core/vdbe/execute.rs
+++ b/core/vdbe/execute.rs
@@ -960,7 +960,7 @@ pub fn op_open_read(
 
             let btree_cursor = Box::new(BTreeCursor::new_table(
                 pager.clone(),
-                *root_page,
+                maybe_transform_root_page_to_positive(mv_store, *root_page),
                 num_columns,
             ));
             let cursor = maybe_promote_to_mvcc_cursor(btree_cursor)?;
@@ -989,7 +989,7 @@ pub fn op_open_read(
             // Regular table
             let btree_cursor = Box::new(BTreeCursor::new_table(
                 pager.clone(),
-                *root_page,
+                maybe_transform_root_page_to_positive(mv_store, *root_page),
                 num_columns,
             ));
             let cursor = maybe_promote_to_mvcc_cursor(btree_cursor)?;
@@ -7134,7 +7134,7 @@ pub fn op_open_write(
             let num_columns = index.columns.len();
             let btree_cursor = Box::new(BTreeCursor::new_index(
                 pager.clone(),
-                root_page,
+                maybe_transform_root_page_to_positive(mv_store, root_page),
                 index.as_ref(),
                 num_columns,
             ));
@@ -7154,7 +7154,7 @@ pub fn op_open_write(
 
             let btree_cursor = Box::new(BTreeCursor::new_table(
                 pager.clone(),
-                root_page,
+                maybe_transform_root_page_to_positive(mv_store, root_page),
                 num_columns,
             ));
             let cursor = maybe_promote_to_mvcc_cursor(btree_cursor)?;
@@ -8106,7 +8106,7 @@ pub fn op_open_dup(
         CursorType::BTreeTable(table) => {
             let cursor = Box::new(BTreeCursor::new_table(
                 pager.clone(),
-                root_page,
+                maybe_transform_root_page_to_positive(mv_store, root_page),
                 table.columns.len(),
             ));
             let cursor: Box<dyn CursorTrait> =
@@ -9222,6 +9222,20 @@ fn get_schema_cookie(
     }
 }
 
+/// A root page in MVCC might still be marked as negative in schema. On restart it is automatically transformed to positive but in other cases
+/// we need to map it to positive if we can in case checkpoint happened.
+fn maybe_transform_root_page_to_positive(mvcc_store: Option<&Arc<MvStore>>, root_page: i64) -> i64 {
+    if let Some(mvcc_store) = mvcc_store {
+        if root_page < 0 {
+            mvcc_store.get_real_table_id(root_page)
+        } else {
+            root_page
+        }
+    } else {
+        root_page
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;