diff --git a/core/translate/emitter.rs b/core/translate/emitter.rs
index 11b0110ae..cf6526fdf 100644
--- a/core/translate/emitter.rs
+++ b/core/translate/emitter.rs
@@ -963,6 +963,9 @@ fn inner_loop_source_emit(
                         }
                     }
                     ResultSetColumn::Agg(agg) => {
+                        // TODO: implement a custom equality check for expressions
+                        // there are lots of examples where this breaks, even simple ones like
+                        // sum(x) != SUM(x)
                         let found = order_by
                             .iter()
                             .enumerate()
@@ -1525,6 +1528,9 @@ fn group_by_emit(
                     }
                 }
                 ResultSetColumn::Agg(agg) => {
+                    // TODO: implement a custom equality check for expressions
+                    // there are lots of examples where this breaks, even simple ones like
+                    // sum(x) != SUM(x)
                     let found = order_by
                         .iter()
                         .enumerate()
diff --git a/core/translate/expr.rs b/core/translate/expr.rs
index a2f373e82..5ce5b5537 100644
--- a/core/translate/expr.rs
+++ b/core/translate/expr.rs
@@ -568,6 +568,9 @@ pub fn translate_expr(
 ) -> Result<usize> {
     if let Some(precomputed_exprs_to_registers) = precomputed_exprs_to_registers {
         for (precomputed_expr, reg) in precomputed_exprs_to_registers.iter() {
+            // TODO: implement a custom equality check for expressions
+            // there are lots of examples where this breaks, even simple ones like
+            // sum(x) != SUM(x)
             if expr == *precomputed_expr {
                 program.emit_insn(Insn::Copy {
                     src_reg: *reg,