From 5820f691afedb46d4c4b15ceca7298c53c34d8c2 Mon Sep 17 00:00:00 2001
From: Jussi Saurio <jussi.saurio@gmail.com>
Date: Mon, 8 Sep 2025 16:21:34 +0300
Subject: [PATCH] fix: do not crash in Next if cursor stack has no pages

---
 core/storage/btree.rs |  5 ++++-
 testing/join.test     | 12 +++++++++++-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/core/storage/btree.rs b/core/storage/btree.rs
index 8b37dc64b..3c732c8d9 100644
--- a/core/storage/btree.rs
+++ b/core/storage/btree.rs
@@ -1203,6 +1203,10 @@ impl BTreeCursor {
                 }
                 None => return Ok(IOResult::Done(false)),
             }
+        } else if self.stack.current_page == -1 {
+            // This can happen in nested left joins. See:
+            // https://github.com/tursodatabase/turso/issues/2924
+            return Ok(IOResult::Done(false));
         }
         loop {
             let mem_page = self.stack.top_ref();
@@ -4202,7 +4206,6 @@ impl BTreeCursor {
         if self.valid_state == CursorValidState::Invalid {
             return Ok(IOResult::Done(false));
         }
-
         loop {
             match self.advance_state {
                 AdvanceState::Start => {
diff --git a/testing/join.test b/testing/join.test
index 44434e971..034719b1f 100755
--- a/testing/join.test
+++ b/testing/join.test
@@ -318,4 +318,14 @@ do_execsql_test_on_specific_db {:memory:} left-join-seek-key-regression-test {
   CREATE TABLE u (x INTEGER PRIMARY KEY);
   INSERT INTO t VALUES (1);
   SELECT * FROM t LEFT JOIN u ON false WHERE u.x = 1; 
-} {}
\ No newline at end of file
+} {}
+
+# regression test for issue 2924: calling Next on a cursor that hasn't moved yet
+do_execsql_test_on_specific_db {:memory:} next-crash {
+  create table a(x int primary key,y);
+  create table b(x int primary key,y);
+  create table c(x int primary key,y);
+  insert into a values (1,1),(2,2);
+  select a.x, b.x, c.x from a left join b on a.y=b.x left join c on b.y=c.x;
+} {1||
+2||}