crash when truncate table in transcation

[lysu]

Bug Report

1. What did you do?
   If possible, provide a recipe for reproducing the error.

mysql> create table ut(a int, primary key(a));
Query OK, 0 rows affected (0.04 sec)

mysql> insert into ut values (1);
Query OK, 1 row affected (0.00 sec)

mysql> begin;
Query OK, 0 rows affected (0.00 sec)

mysql> insert into ut values (1);
Query OK, 1 row affected (0.01 sec)

mysql> truncate ut;
ERROR 2013 (HY000): Lost connection to MySQL server during query
mysql> 

2. What did you expect to see?

should not crash

3. What did you see instead?

process crashed with

2018/10/31 22:18:41.403 session.go:368: [warning] con:1 finished txn:{<nil> <nil> 0xc0083c8a60 map[] [] <nil>}, [kv:1062]Duplicate entry '1' for key 'PRIMARY'
2018/10/31 22:18:41.404 conn.go:427: [error] lastCmd truncate ut, runtime error: invalid memory address or nil pointer dereference, goroutine 1313 [running]:
github.com/pingcap/tidb/server.(*clientConn).Run.func1(0xc00806d860, 0xc000767bf0)
	/home/robi/Code/go/src/github.com/pingcap/tidb/server/conn.go:425 +0xc2
panic(0x175ca40, 0x2a3abc0)
	/home/robi/go1.11.1/src/runtime/panic.go:513 +0x1e6
github.com/pingcap/tidb/executor.(*DDLExec).toErr(0xc009675180, 0x1c0cd60, 0xc0086d7f40, 0x0, 0x0)
	/home/robi/Code/go/src/github.com/pingcap/tidb/executor/ddl.go:57 +0x183
github.com/pingcap/tidb/executor.(*DDLExec).Next(0xc009675180, 0x7f067eafa0c0, 0xc008e5bfc0, 0xc008e80b40, 0x1c0cd60, 0xc0086d7f40)
	/home/robi/Code/go/src/github.com/pingcap/tidb/executor/ddl.go:94 +0x2d3
github.com/pingcap/tidb/executor.(*ExecStmt).handleNoDelayExecutor(0xc00a121f80, 0x7f067eafa0c0, 0xc008e5bfc0, 0x1c43600, 0xc0083c5ea0, 0x1c24d80, 0xc009675180, 0x0, 0x0, 0x0, ...)
	/home/robi/Code/go/src/github.com/pingcap/tidb/executor/adapter.go:270 +0x23d
github.com/pingcap/tidb/executor.(*ExecStmt).Exec(0xc00a121f80, 0x7f067eafa0c0, 0xc008e5bfc0, 0x0, 0x0, 0x0, 0x0)
	/home/robi/Code/go/src/github.com/pingcap/tidb/executor/adapter.go:234 +0xb10
github.com/pingcap/tidb/session.runStmt(0x7f067eafa0c0, 0xc008e5bfc0, 0x1c43600, 0xc0083c5ea0, 0x1c21500, 0xc00a121f80, 0x0, 0x0, 0x0, 0x0)
	/home/robi/Code/go/src/github.com/pingcap/tidb/session/tidb.go:148 +0xd0
github.com/pingcap/tidb/session.(*session).executeStatement(0xc0083c5ea0, 0x7f067eafa0c0, 0xc008e5bfc0, 0x1, 0x1c201c0, 0xc0086d7880, 0x1c21500, 0xc00a121f80, 0x0, 0x0, ...)
	/home/robi/Code/go/src/github.com/pingcap/tidb/session/session.go:734 +0x24d
github.com/pingcap/tidb/session.(*session).execute(0xc0083c5ea0, 0x7f067eafa0c0, 0xc008e5bfc0, 0xc00976c7c1, 0xb, 0x0, 0x0, 0x0, 0x0, 0x0)
	/home/robi/Code/go/src/github.com/pingcap/tidb/session/session.go:805 +0xf1d
github.com/pingcap/tidb/session.(*session).Execute(0xc0083c5ea0, 0x7f067eafa0c0, 0xc008e5bfc0, 0xc00976c7c1, 0xb, 0x0, 0x0, 0x0, 0x0, 0x0)
	/home/robi/Code/go/src/github.com/pingcap/tidb/session/session.go:755 +0xa4
github.com/pingcap/tidb/server.(*TiDBContext).Execute(0xc0083ee450, 0x7f067eafa0c0, 0xc008e5bfc0, 0xc00976c7c1, 0xb, 0x0, 0x0, 0x0, 0x0, 0x0)
	/home/robi/Code/go/src/github.com/pingcap/tidb/server/driver_tidb.go:239 +0xc4
github.com/pingcap/tidb/server.(*clientConn).handleQuery(0xc00806d860, 0x7f067eafa0c0, 0xc008e5bfc0, 0xc00976c7c1, 0xb, 0x0, 0x0)
	/home/robi/Code/go/src/github.com/pingcap/tidb/server/conn.go:874 +0xb7
github.com/pingcap/tidb/server.(*clientConn).dispatch(0xc00806d860, 0xc00976c7c1, 0xb, 0xb, 0x0, 0x0)
	/home/robi/Code/go/src/github.com/pingcap/tidb/server/conn.go:626 +0x88d
github.com/pingcap/tidb/server.(*clientConn).Run(0xc00806d860)
	/home/robi/Code/go/src/github.com/pingcap/tidb/server/conn.go:470 +0x458
github.com/pingcap/tidb/server.(*Server).onConn(0xc0071324e0, 0x1c29220, 0xc007a3b958)
	/home/robi/Code/go/src/github.com/pingcap/tidb/server/server.go:324 +0x3b4
created by github.com/pingcap/tidb/server.(*Server).Run
	/home/robi/Code/go/src/github.com/pingcap/tidb/server/server.go:264 +0x7e1

4. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?

+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: None
Git Commit Hash: None
Git Branch: None
UTC Build Time: None
GoVersion: None
Race Enabled: false
TiKV Min Version: 2.1.0-alpha.1-ff3dd160846b7d1aed9079c389fc188f7f5ea13e
Check Table Before Drop: false |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.02 sec)

[zz-jason]

already fixed in: #8056

[lysu]

ok, we meet same question...2333