From 6a2e7d2327e45b411f9ce93f592dd065b7cb7206 Mon Sep 17 00:00:00 2001
From: Mason Liang <mason@scroll.io>
Date: Mon, 6 Nov 2023 15:41:23 -0500
Subject: [PATCH] Add fixed column to lookup_exprs for mpt circuit

---
 src/gadgets/mpt_update.rs |  7 ++++---
 src/mpt.rs                | 10 +++++++---
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/src/gadgets/mpt_update.rs b/src/gadgets/mpt_update.rs
index cedd72c4..5a35e517 100644
--- a/src/gadgets/mpt_update.rs
+++ b/src/gadgets/mpt_update.rs
@@ -45,7 +45,7 @@ lazy_static! {
 }
 
 pub trait MptUpdateLookup<F: FieldExt> {
-    fn lookup(&self) -> [Query<F>; 8];
+    fn lookup(&self) -> [Query<F>; 7];
 }
 
 #[derive(Clone)]
@@ -77,8 +77,10 @@ pub struct MptUpdateConfig {
 }
 
 impl<F: FieldExt> MptUpdateLookup<F> for MptUpdateConfig {
-    fn lookup(&self) -> [Query<F>; 8] {
+    fn lookup(&self) -> [Query<F>; 7] {
         let is_start = || self.segment_type.current_matches(&[SegmentType::Start]);
+        // Note that one non-start rows, all 7 queries will be 0. This corresponds to a valid
+        // mpt proof in that in an empty trie, the zero address has nonce = 0.
         let old_root_rlc = self.second_phase_intermediate_values[0].current() * is_start();
         let new_root_rlc = self.second_phase_intermediate_values[1].current() * is_start();
         let proof_type = self.proof_type.current() * is_start();
@@ -90,7 +92,6 @@ impl<F: FieldExt> MptUpdateLookup<F> for MptUpdateConfig {
             * is_start();
         let storage_key_rlc = self.storage_key_rlc.current() * is_start();
         [
-            is_start().into(),
             address,
             storage_key_rlc,
             proof_type,
diff --git a/src/mpt.rs b/src/mpt.rs
index 12ce206c..da923762 100644
--- a/src/mpt.rs
+++ b/src/mpt.rs
@@ -1,5 +1,5 @@
 use crate::{
-    constraint_builder::{ConstraintBuilder, SelectorColumn},
+    constraint_builder::{ConstraintBuilder, Query, SelectorColumn},
     gadgets::{
         byte_bit::ByteBitGadget,
         byte_representation::ByteRepresentationConfig,
@@ -76,7 +76,6 @@ impl MptCircuitConfig {
         // exist in an mpt with root = 0 (i.e. the mpt is empty).
         let is_final_row = SelectorColumn(cs.fixed_column());
         let padding_row_expressions = [
-            1.into(),
             0.into(),
             0.into(),
             (MPTProofType::AccountDoesNotExist as u64).into(),
@@ -173,7 +172,12 @@ impl MptCircuitConfig {
     }
 
     pub fn lookup_exprs<F: FieldExt>(&self, meta: &mut VirtualCells<'_, F>) -> [Expression<F>; 8] {
-        self.mpt_update.lookup().map(|q| q.run(meta))
+        std::iter::once(Query::from(self.selector.current()))
+            .chain(self.mpt_update.lookup().into_iter())
+            .map(|q| q.run(meta))
+            .collect::<Vec<_>>()
+            .try_into()
+            .unwrap()
     }
 
     /// The number of minimum number of rows required for the mpt circuit.