From cdaea7f27440535c851c2a18a3eeee263aaff8c5 Mon Sep 17 00:00:00 2001
From: Pekka Enberg <penberg@iki.fi>
Date: Mon, 11 Aug 2025 12:26:11 +0300
Subject: [PATCH] core/vdbe: Make apply_view_deltas() return early if views are
 disabled

Currently, we have a borrow problem because parse_schema_rows() already
borrows `schema`, but then `apply_view_deltas` does the same:

```
thread 'main' panicked at core/vdbe/mod.rs:450:49:
already mutably borrowed: BorrowError
stack backtrace:
   0: __rustc::rust_begin_unwind
             at /rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/library/std/src/panicking.rs:697:5
   1: core::panicking::panic_fmt
             at /rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/library/core/src/panicking.rs:75:14
   2: core::cell::panic_already_mutably_borrowed
             at /rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/library/core/src/cell.rs:799:5
   3: core::cell::RefCell<T>::borrow
             at /rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/library/core/src/cell.rs:987:25
   4: turso_core::vdbe::Program::apply_view_deltas
             at ./core/vdbe/mod.rs:450:26
   5: turso_core::vdbe::Program::commit_txn
             at ./core/vdbe/mod.rs:468:9
   6: turso_core::vdbe::execute::op_halt
             at ./core/vdbe/execute.rs:1954:15
   7: turso_core::vdbe::Program::step
             at ./core/vdbe/mod.rs:430:19
   8: turso_core::Statement::step
             at ./core/lib.rs:1914:23
   9: turso_core::util::parse_schema_rows
             at ./core/util.rs:91:15
  10: turso_core::Connection::parse_schema_rows::{{closure}}
             at ./core/lib.rs:1518:17
  11: turso_core::Connection::with_schema_mut
             at ./core/lib.rs:1625:9
  12: turso_core::Connection::parse_schema_rows
             at ./core/lib.rs:1515:9
```

However, this is a read transaction and views are not even enabled,
let's just make `apply_view_deltas()` return early if there's no
processing needed, to skip the schema borrow altogether.
---
 core/vdbe/mod.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/core/vdbe/mod.rs b/core/vdbe/mod.rs
index a31105c1d..259767031 100644
--- a/core/vdbe/mod.rs
+++ b/core/vdbe/mod.rs
@@ -444,6 +444,10 @@ impl Program {
 
     #[instrument(skip_all, level = Level::DEBUG)]
     fn apply_view_deltas(&self, rollback: bool) {
+        if self.connection.view_transaction_states.borrow().is_empty() {
+            return;
+        }
+
         let tx_states = self.connection.view_transaction_states.take();
 
         if !rollback {