From 192ccba88fb513956e0668b7783c69b8016f888b Mon Sep 17 00:00:00 2001
From: Igor Aleksanov <popzxc@yandex.ru>
Date: Fri, 16 Apr 2021 10:41:24 +0300
Subject: [PATCH 1/2] Fix loading the last block number in state keeper

---
 core/bin/zksync_core/src/state_keeper/mod.rs | 11 +++++++++++
 core/lib/storage/sqlx-data.json              | 18 ++++++++++++++++++
 core/lib/storage/src/chain/block/mod.rs      | 14 +++++++++++++-
 3 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/core/bin/zksync_core/src/state_keeper/mod.rs b/core/bin/zksync_core/src/state_keeper/mod.rs
index ba024885a9..4b6f14dd66 100644
--- a/core/bin/zksync_core/src/state_keeper/mod.rs
+++ b/core/bin/zksync_core/src/state_keeper/mod.rs
@@ -289,6 +289,17 @@ impl ZkSyncStateInitParams {
                 "restored root_hash is different"
             );
         }
+
+        // We have to load actual number of the last committed block, since above we load the block number from state,
+        // and in case of empty block being sealed (that may happen because of bug).
+        let last_actually_committed_block_number = storage
+            .chain()
+            .block_schema()
+            .get_last_saved_block()
+            .await?;
+
+        let block_number = std::cmp::max(last_actually_committed_block_number, block_number);
+
         Ok(block_number)
     }
 
diff --git a/core/lib/storage/sqlx-data.json b/core/lib/storage/sqlx-data.json
index 1761eb8589..b2b78fa306 100644
--- a/core/lib/storage/sqlx-data.json
+++ b/core/lib/storage/sqlx-data.json
@@ -3428,6 +3428,24 @@
       ]
     }
   },
+  "bf88992c521353535925401702028307ba3d79dfa2e60d939a117e7aae5a6403": {
+    "query": "SELECT MAX(number) FROM blocks",
+    "describe": {
+      "columns": [
+        {
+          "ordinal": 0,
+          "name": "max",
+          "type_info": "Int8"
+        }
+      ],
+      "parameters": {
+        "Left": []
+      },
+      "nullable": [
+        null
+      ]
+    }
+  },
   "c0bc09d944da0d6a2eb2108185c757ff16440ed9c3d1fb2835cf3d4f552078f2": {
     "query": "SELECT * FROM executed_priority_operations WHERE block_number = $1",
     "describe": {
diff --git a/core/lib/storage/src/chain/block/mod.rs b/core/lib/storage/src/chain/block/mod.rs
index d296a20656..5b8d95614b 100644
--- a/core/lib/storage/src/chain/block/mod.rs
+++ b/core/lib/storage/src/chain/block/mod.rs
@@ -491,7 +491,19 @@ impl<'a, 'c> BlockSchema<'a, 'c> {
         result
     }
 
-    /// Returns the number of last block
+    /// Returns the number of last block saved to the database.
+    pub async fn get_last_saved_block(&mut self) -> QueryResult<BlockNumber> {
+        let start = Instant::now();
+        let count = sqlx::query!("SELECT MAX(number) FROM blocks")
+            .fetch_one(self.0.conn())
+            .await?
+            .max
+            .unwrap_or(0);
+        metrics::histogram!("sql.chain.block.get_last_committed_block", start.elapsed());
+        Ok(BlockNumber(count as u32))
+    }
+
+    /// Returns the number of last block for which an aggregated operation exists.
     pub async fn get_last_committed_block(&mut self) -> QueryResult<BlockNumber> {
         let start = Instant::now();
         let result = OperationsSchema(self.0)

From 1b149c50721e1e0b5941cf8328b50bf370a4c67b Mon Sep 17 00:00:00 2001
From: Igor Aleksanov <popzxc@yandex.ru>
Date: Fri, 16 Apr 2021 10:43:46 +0300
Subject: [PATCH 2/2] Move loading actual block number before checking the root
 hash

---
 core/bin/zksync_core/src/state_keeper/mod.rs | 23 +++++++++++---------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/core/bin/zksync_core/src/state_keeper/mod.rs b/core/bin/zksync_core/src/state_keeper/mod.rs
index 4b6f14dd66..5572c2c54f 100644
--- a/core/bin/zksync_core/src/state_keeper/mod.rs
+++ b/core/bin/zksync_core/src/state_keeper/mod.rs
@@ -276,6 +276,19 @@ impl ZkSyncStateInitParams {
                 }
             }
         }
+
+        // We have to load actual number of the last committed block, since above we load the block number from state,
+        // and in case of empty block being sealed (that may happen because of bug).
+        // Note that if this block is greater than the `block_number`, it means that some empty blocks were committed,
+        // so the root hash has not changed and we don't need to update the tree in order to get the right root hash.
+        let last_actually_committed_block_number = storage
+            .chain()
+            .block_schema()
+            .get_last_saved_block()
+            .await?;
+
+        let block_number = std::cmp::max(last_actually_committed_block_number, block_number);
+
         if *block_number != 0 {
             let storage_root_hash = storage
                 .chain()
@@ -290,16 +303,6 @@ impl ZkSyncStateInitParams {
             );
         }
 
-        // We have to load actual number of the last committed block, since above we load the block number from state,
-        // and in case of empty block being sealed (that may happen because of bug).
-        let last_actually_committed_block_number = storage
-            .chain()
-            .block_schema()
-            .get_last_saved_block()
-            .await?;
-
-        let block_number = std::cmp::max(last_actually_committed_block_number, block_number);
-
         Ok(block_number)
     }