fix: error occurred when retrying transaction on empty table (#18703)

* fix: error occurred when retrying transaction on empty table

* add stateless test case

* refine stateless test

* fix typo

---------

Co-authored-by: dantengsky <[email protected]>

Author: SkyFan2002

src/query/storages/fuse/src/retry/commit.rs

@@ -153,48 +153,50 @@ async fn try_rebuild_req(
             if let Some(txn_begin_timestamp) =
                 txn_mgr.get_table_txn_begin_timestamp(latest_table.get_id())
             {
-                let Some(latest_snapshot_timestamp) = latest_snapshot.timestamp() else {
-                    return Err(ErrorCode::UnresolvableConflict(format!(
+                if let Some(latest_snapshot) = latest_snapshot.as_ref() {
+                    let Some(latest_snapshot_timestamp) = latest_snapshot.timestamp else {
+                        return Err(ErrorCode::UnresolvableConflict(format!(
                         "Table {} snapshot lacks required timestamp. This table was created with a significantly outdated version that is no longer directly supported by the current version and requires migration.
                          Please contact us at https://www.databend.com/contact-us/ or email [email protected]",
                         tid
                     )));
-                };
-
-                // By enforcing txn_begin_timestamp >= latest_snapshot_timestamp, we ensure that
-                // vacuum operations won't remove table data (segment, blocks, etc.) that newly
-                // created in the current active transaction.
-
-                // In the current transaction, all the newly created table data (segments, blocks, etc.)
-                // has timestamps that are greater than or equal to txn_begin_timestamp, but the
-                // final snapshot which contains those data (and is yet to be committed) may have a timestamp
-                // that is larger than txn_begin_timestamp.
-
-                // To maintain vacuum safety, we must ensure that if the latest snapshot's timestamp
-                // (latest_snapshot_timestamp) is larger than txn_begin_timestamp, we abort the transaction
-                // to prevent potential data loss during vacuum operations.
-
-                // Example:
-                // session1:                                      session2:                    session3:
-                // begin;
-                // -- newly created table data
-                // -- timestamped as A
-                // insert into t values (1);
-                //                                              -- new snapshot S's ts is B
-                //                                              insert into t values (2);
-                //                                                                             -- using S as gc root
-                //                                                                             -- if B > A, then newly created table data
-                //                                                                             -- in session1 will be purged
-                //                                                                             call fuse_vacuum2('db', 't');
-                // -- while merging with S
-                // -- if A < B, this txn should abort
-                // commit;
-
-                if txn_begin_timestamp < latest_snapshot_timestamp {
-                    return Err(ErrorCode::UnresolvableConflict(format!(
+                    };
+
+                    // By enforcing txn_begin_timestamp >= latest_snapshot_timestamp, we ensure that
+                    // vacuum operations won't remove table data (segment, blocks, etc.) that newly
+                    // created in the current active transaction.
+
+                    // In the current transaction, all the newly created table data (segments, blocks, etc.)
+                    // has timestamps that are greater than or equal to txn_begin_timestamp, but the
+                    // final snapshot which contains those data (and is yet to be committed) may have a timestamp
+                    // that is larger than txn_begin_timestamp.
+
+                    // To maintain vacuum safety, we must ensure that if the latest snapshot's timestamp
+                    // (latest_snapshot_timestamp) is larger than txn_begin_timestamp, we abort the transaction
+                    // to prevent potential data loss during vacuum operations.
+
+                    // Example:
+                    // session1:                                      session2:                    session3:
+                    // begin;
+                    // -- newly created table data
+                    // -- timestamped as A
+                    // insert into t values (1);
+                    //                                              -- new snapshot S's ts is B
+                    //                                              insert into t values (2);
+                    //                                                                             -- using S as gc root
+                    //                                                                             -- if B > A, then newly created table data
+                    //                                                                             -- in session1 will be purged
+                    //                                                                             call fuse_vacuum2('db', 't');
+                    // -- while merging with S
+                    // -- if A < B, this txn should abort
+                    // commit;
+
+                    if txn_begin_timestamp < latest_snapshot_timestamp {
+                        return Err(ErrorCode::UnresolvableConflict(format!(
                        "Unresolvable conflict detected for table {} while resolving conflicts: txn started with logical timestamp {}, which is less than the latest table timestamp {}. Transaction must be aborted.",
                         tid, txn_begin_timestamp, latest_snapshot_timestamp
                     )));
+                    }
                 }
             }
         }

tests/suites/0_stateless/01_transaction/01_03_issue_18705.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python3
+
+import mysql.connector
+
+# https://github.com/databendlabs/databend/issues/18705
+if __name__ == "__main__":
+    # Session 1:
+    # Insert into empty table
+    mdb = mysql.connector.connect(host="127.0.0.1", user="root", passwd="root", port="3307")
+    mycursor = mdb.cursor()
+    mycursor.execute("create or replace table t_18705(c int)")
+    mycursor.fetchall()
+    mycursor.execute("begin")
+    mycursor.fetchall()
+    mycursor.execute("insert into t_18705 values (1)")
+    mycursor.fetchall()
+
+    # Session 2:
+    # Alter table in another session, so that the new table after alter operation will still be empty
+    mydb_alter_tbl = mysql.connector.connect(host="127.0.0.1", user="root", passwd="root", port="3307")
+    mycursor_alter_tbl = mydb_alter_tbl.cursor()
+    mycursor_alter_tbl.execute("alter table t_18705 SET OPTIONS (block_per_segment = 500)")
+    mycursor_alter_tbl.fetchall()
+
+    # Session 1:
+    # Try commit the txn in session one
+    mycursor.execute("commit")
+    mycursor.fetchall()
+
+    # Will not reach here, if `commit` failed
+    print("Looks good")

tests/suites/0_stateless/01_transaction/01_03_issue_18705.result

@@ -0,0 +1 @@
+Looks good