*: insufficient bytes decode value reported when adding index for some split common-handled tables. #20727
Description
Bug Report
Please answer these questions before submitting your issue. Thanks!
1. Minimal reproduce step (Required)
tidb> show variables like '%clustered%';
+-----------------------------+-------+
| Variable_name | Value |
+-----------------------------+-------+
| tidb_enable_clustered_index | ON |
+-----------------------------+-------+
1 row in set (0.02 sec)
tidb> create table t (a varchar(255), b int, primary key(a));
Query OK, 0 rows affected (0.02 sec)
tidb> insert into t values ('a', 1), ('b', 2), ('c', 3), ('u', 1);
Query OK, 4 rows affected (0.00 sec)
Records: 4 Duplicates: 0 Warnings: 0
tidb> split table t between ('a') and ('z') regions 5;
+--------------------+----------------------+
| TOTAL_SPLIT_REGION | SCATTER_FINISH_RATIO |
+--------------------+----------------------+
| 4 | 1 |
+--------------------+----------------------+
1 row in set (0.01 sec)
tidb> create index idx on t (b);
2. What did you expect to see? (Required)
The job ran successfully.
3. What did you see instead (Required)
Error reported when executing the DDL job:
[worker="worker 2, tp add index"] [error="insufficient bytes to decode value"] [errorVerbose="insufficient bytes to decode value
github.com/pingcap/tidb/util/codec.peekBytes
/home/bb7133/Projects/gopath/src/github.com/pingcap/tidb/util/codec/codec.go:958
github.com/pingcap/tidb/util/codec.peek
/home/bb7133/Projects/gopath/src/github.com/pingcap/tidb/util/codec/codec.go:933
github.com/pingcap/tidb/util/codec.CutOne
/home/bb7133/Projects/gopath/src/github.com/pingcap/tidb/util/codec/codec.go:887
github.com/pingcap/tidb/kv.NewCommonHandle
/home/bb7133/Projects/gopath/src/github.com/pingcap/tidb/kv/key.go:248
github.com/pingcap/tidb/tablecodec.DecodeRowKey
/home/bb7133/Projects/gopath/src/github.com/pingcap/tidb/tablecodec/tablecodec.go:269
github.com/pingcap/tidb/ddl.decodeHandleRange
/home/bb7133/Projects/gopath/src/github.com/pingcap/tidb/ddl/backfilling.go:364
github.com/pingcap/tidb/ddl.(*worker).sendRangeTaskToWorkers
/home/bb7133/Projects/gopath/src/github.com/pingcap/tidb/ddl/backfilling.go:380
github.com/pingcap/tidb/ddl.(*worker).writePhysicalTableRecord
/home/bb7133/Projects/gopath/src/github.com/pingcap/tidb/ddl/backfilling.go:563
github.com/pingcap/tidb/ddl.(*worker).addPhysicalTableIndex
/home/bb7133/Projects/gopath/src/github.com/pingcap/tidb/ddl/index.go:1142
github.com/pingcap/tidb/ddl.(*worker).addTableIndex
/home/bb7133/Projects/gopath/src/github.com/pingcap/tidb/ddl/index.go:1165
github.com/pingcap/tidb/ddl.(*worker).onCreateIndex.func1
/home/bb7133/Projects/gopath/src/github.com/pingcap/tidb/ddl/index.go:564
github.com/pingcap/tidb/ddl.(*worker).runReorgJob.func1
/home/bb7133/Projects/gopath/src/github.com/pingcap/tidb/ddl/reorg.go:190
runtime.goexit
/home/bb7133/Softwares/go/src/runtime/asm_amd64.s:1374"]
4. What is your TiDB version? (Required)
This can be reproduced in the master version
Root Cause
For now, ADD INDEX(as well as some other DDL jobs that need data-reorganization) assume that the 'startKey' and 'endKey' of a region can always be decoded:
Line 359 in 937949f
But it is not the case for:
- The previous versions of TiDB-Lightning(backend/local: use range properties to optimize region range estimate tidb-lightning#422)
- Explicit
SPLIT TABLEfor clustered index.