From cd3b4bccd38177f4b179ffc4822908b3cbdf0070 Mon Sep 17 00:00:00 2001
From: Jussi Saurio <jussi.saurio@gmail.com>
Date: Thu, 14 Aug 2025 15:08:22 +0300
Subject: [PATCH] Fix UPDATE: Do not use an index for iteration if that index
 is going to be updated

Closes #2598
---
 core/translate/optimizer/mod.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/core/translate/optimizer/mod.rs b/core/translate/optimizer/mod.rs
index 9b84cd9f1..a290f6c0f 100644
--- a/core/translate/optimizer/mod.rs
+++ b/core/translate/optimizer/mod.rs
@@ -129,6 +129,26 @@ fn optimize_update_plan(plan: &mut UpdatePlan, schema: &Schema) -> Result<()> {
         &mut plan.order_by,
         &mut None,
     )?;
+
+    let table_ref = &mut plan.table_references.joined_tables_mut()[0];
+    // It is not safe to use an index that is going to be updated as the iteration index for a table.
+    // In these cases, we will fall back to a table scan.
+    // FIXME: this should probably be incorporated into the optimizer itself, but it's a smaller fix this way.
+    if table_ref
+        .op
+        .index()
+        .is_some_and(|index| plan.indexes_to_update.iter().any(|i| Arc::ptr_eq(index, i)))
+    {
+        table_ref.op = Operation::Scan(Scan::BTreeTable {
+            iter_dir: IterationDirection::Forwards,
+            index: None,
+        });
+        // Revert the decision to use a WHERE clause term as an index constraint.
+        plan.where_clause
+            .iter_mut()
+            .for_each(|term| term.consumed = false);
+    }
+
     Ok(())
 }