drainer: fix failure to update BIT columns with downstream TiDB

drainer/translator/mysql.go

@@ -256,7 +256,12 @@ func formatData(data types.Datum, ft types.FieldType) (types.Datum, error) {
 	case mysql.TypeSet:
 		data = types.NewDatum(data.GetMysqlSet().Value)
 	case mysql.TypeBit:
-		data = types.NewDatum(data.GetBytes())
+		// Encode bits as integers to avoid pingcap/tidb#10988 (which also affects MySQL itself)
+		val, err := data.GetBinaryLiteral().ToInt(nil)
+		if err != nil {
+			return types.Datum{}, err
+		}
+		data = types.NewUintDatum(val)
 	}
 
 	return data, nil

tests/update_bit1/drainer.toml

@@ -0,0 +1,18 @@
+detect-interval = 10
+data-dir = '/tmp/tidb_binlog_test/update_bit1'
+pd-urls = 'http://127.0.0.1:2379'
+
+[syncer]
+ignore-schemas = 'INFORMATION_SCHEMA,PERFORMANCE_SCHEMA,mysql'
+txn-batch = 1
+worker-count = 1
+disable-dispatch = false
+safe-mode = false
+db-type = 'mysql'
+replicate-do-db = ['update_bit1']
+
+[syncer.to]
+host = '127.0.0.1'
+user = 'root'
+password = ''
+port = 3306

tests/update_bit1/run.sh

@@ -0,0 +1,28 @@
+#!/bin/sh
+
+set -e
+
+cd "$(dirname "$0")"
+
+run_drainer &
+
+run_sql 'DROP DATABASE IF EXISTS update_bit1;'
+run_sql 'CREATE DATABASE update_bit1;'
+run_sql 'CREATE TABLE update_bit1.t(a BIT(1) NOT NULL);'
+run_sql 'INSERT INTO update_bit1.t VALUES (0x01);'
+
+sleep 3
+
+down_run_sql 'SELECT HEX(a) FROM update_bit1.t;'
+check_contains 'HEX(a): 1'
+
+# Verify fix for TOOL-1346.
+
+run_sql 'UPDATE update_bit1.t SET a = 0x00;'
+
+sleep 3
+
+down_run_sql 'SELECT HEX(a) FROM update_bit1.t;'
+check_contains 'HEX(a): 0'
+
+killall drainer