From 34978d0fde1a5aae8d4347a46729e9da6423b7c4 Mon Sep 17 00:00:00 2001
From: Jussi Saurio <jussi.saurio@gmail.com>
Date: Thu, 13 Nov 2025 09:32:37 +0200
Subject: [PATCH] Store Cow<&Expr> in expr_to_reg_cache

We will be storing owned expressions in it for RETURNING in a later commit.
---
 core/translate/aggregation.rs |  8 ++++----
 core/translate/emitter.rs     |  2 +-
 core/translate/group_by.rs    | 18 ++++++++++++------
 core/translate/window.rs      | 10 +++++-----
 4 files changed, 22 insertions(+), 16 deletions(-)

diff --git a/core/translate/aggregation.rs b/core/translate/aggregation.rs
index 52a19962b..d55a8927a 100644
--- a/core/translate/aggregation.rs
+++ b/core/translate/aggregation.rs
@@ -38,10 +38,10 @@ pub fn emit_ungrouped_aggregation<'a>(
     // we need to call translate_expr on each result column, but replace the expr with a register copy in case any part of the
     // result column expression matches a) a group by column or b) an aggregation result.
     for (i, agg) in plan.aggregates.iter().enumerate() {
-        t_ctx
-            .resolver
-            .expr_to_reg_cache
-            .push((&agg.original_expr, agg_start_reg + i));
+        t_ctx.resolver.expr_to_reg_cache.push((
+            std::borrow::Cow::Borrowed(&agg.original_expr),
+            agg_start_reg + i,
+        ));
     }
     t_ctx.resolver.enable_expr_to_reg_cache();
 
diff --git a/core/translate/emitter.rs b/core/translate/emitter.rs
index 49e2f485e..2a9ff3508 100644
--- a/core/translate/emitter.rs
+++ b/core/translate/emitter.rs
@@ -51,7 +51,7 @@ pub struct Resolver<'a> {
     pub schema: &'a Schema,
     pub symbol_table: &'a SymbolTable,
     pub expr_to_reg_cache_enabled: bool,
-    pub expr_to_reg_cache: Vec<(&'a ast::Expr, usize)>,
+    pub expr_to_reg_cache: Vec<(std::borrow::Cow<'a, ast::Expr>, usize)>,
 }
 
 impl<'a> Resolver<'a> {
diff --git a/core/translate/group_by.rs b/core/translate/group_by.rs
index aa5e5dcdc..4d0c12a18 100644
--- a/core/translate/group_by.rs
+++ b/core/translate/group_by.rs
@@ -646,7 +646,10 @@ pub fn group_by_process_single_group(
             {
                 if *in_result {
                     program.emit_column_or_rowid(*pseudo_cursor, sorter_column_index, next_reg);
-                    t_ctx.resolver.expr_to_reg_cache.push((expr, next_reg));
+                    t_ctx
+                        .resolver
+                        .expr_to_reg_cache
+                        .push((std::borrow::Cow::Borrowed(expr), next_reg));
                     next_reg += 1;
                 }
             }
@@ -669,7 +672,10 @@ pub fn group_by_process_single_group(
                     dest_reg,
                     &t_ctx.resolver,
                 )?;
-                t_ctx.resolver.expr_to_reg_cache.push((expr, dest_reg));
+                t_ctx
+                    .resolver
+                    .expr_to_reg_cache
+                    .push((std::borrow::Cow::Borrowed(expr), dest_reg));
             }
         }
     }
@@ -792,10 +798,10 @@ pub fn group_by_emit_row_phase<'a>(
             register: agg_result_reg,
             func: agg.func.clone(),
         });
-        t_ctx
-            .resolver
-            .expr_to_reg_cache
-            .push((&agg.original_expr, agg_result_reg));
+        t_ctx.resolver.expr_to_reg_cache.push((
+            std::borrow::Cow::Borrowed(&agg.original_expr),
+            agg_result_reg,
+        ));
     }
 
     t_ctx.resolver.enable_expr_to_reg_cache();
diff --git a/core/translate/window.rs b/core/translate/window.rs
index ad62e31fc..8a2bae2b3 100644
--- a/core/translate/window.rs
+++ b/core/translate/window.rs
@@ -526,10 +526,10 @@ pub fn init_window<'a>(
     let reg_acc_start = program.alloc_registers(window_function_count);
     let reg_acc_result_start = program.alloc_registers(window_function_count);
     for (i, func) in window.functions.iter().enumerate() {
-        t_ctx
-            .resolver
-            .expr_to_reg_cache
-            .push((&func.original_expr, reg_acc_result_start + i));
+        t_ctx.resolver.expr_to_reg_cache.push((
+            std::borrow::Cow::Borrowed(&func.original_expr),
+            reg_acc_result_start + i,
+        ));
     }
 
     // The same approach applies to expressions referencing the subquery (columns).
@@ -543,7 +543,7 @@ pub fn init_window<'a>(
         t_ctx
             .resolver
             .expr_to_reg_cache
-            .push((expr, reg_col_start + i));
+            .push((std::borrow::Cow::Borrowed(expr), reg_col_start + i));
     }
 
     t_ctx.meta_window = Some(WindowMetadata {