*: insufficient bytes decode value reported when adding index for some split common-handled tables.

[bb7133]

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:

tidb/ddl/backfilling.go

Line 359 in 937949f

func decodeHandleRange(keyRange kv.KeyRange) (kv.Handle, kv.Handle, error) {

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 TABLE for clustered index.

[ti-srebot]

Please edit this comment to complete the following information

Bug

1. Root Cause Analysis (RCA) (optional)

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:

tidb/ddl/backfilling.go

Line 359 in 937949f

func decodeHandleRange(keyRange kv.KeyRange) (kv.Handle, kv.Handle, error) {

2. Symptom (optional)

Report error: insufficient bytes to decode value.

3. All Trigger Conditions (optional)

• Enable clustered index.
• Split table with SPLIT ... BETWEEN ... statement.
• Add index / Change column type / Drop partition with global index

4. Workaround (optional)

No workaround.

5. Affected versions

unreleased

6. Fixed versions

master

[ti-srebot]

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