Aggregation distinct function panic when distinct_agg_push_down and enable_cascades_planner

[lilinghai]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create table t(a int);
insert into t values(-1);
set @@tidb_opt_distinct_agg_push_down=on;
set @@tidb_enable_cascades_planner=on;
select count(*) from t group by a having avg(distinct a)>1;

The query plan is

+--------------------------------+---------+-----------+---------------+----------------------------------------------------------------------------------------+
| id                             | estRows | task      | access object | operator info                                                                          |
+--------------------------------+---------+-----------+---------------+----------------------------------------------------------------------------------------+
| Projection_12                  | 0.80    | root      |               | Column#3                                                                               |
| └─Selection_13                 | 0.80    | root      |               | gt(Column#4, 1)                                                                        |
|   └─HashAgg_18                 | 1.00    | root      |               | group by:rs.t.a, funcs:count(Column#6)->Column#3, funcs:avg(distinct rs.t.a)->Column#4 |
|     └─TableReader_19           | 1.00    | root      |               | data:HashAgg_20                                                                        |
|       └─HashAgg_20             | 1.00    | cop[tikv] |               | group by:rs.t.a, funcs:count(1)->Column#6                                              |
|         └─TableFullScan_17     | 1.00    | cop[tikv] | table:t       | keep order:false, stats:pseudo                                                         |
+--------------------------------+---------+-----------+---------------+----------------------------------------------------------------------------------------+

2. What did you expect to see? (Required)

successfully

3. What did you see instead (Required)

ERROR 1105 (HY000): runtime error: index out of range [-1]
Panic log

err="runtime error: index out of range [-1]
github.com/pingcap/tidb/executor.(*recordSet).Next.func1
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/executor/adapter.go:138
runtime.gopanic
\t/usr/local/go/src/runtime/panic.go:679
runtime.goPanicIndex
\t/usr/local/go/src/runtime/panic.go:75
github.com/pingcap/tidb/types.(*MyDecimal).WriteBin
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/types/mydecimal.go:1197
github.com/pingcap/tidb/types.(*MyDecimal).ToBin
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/types/mydecimal.go:1174
github.com/pingcap/tidb/types.(*MyDecimal).ToHashKey
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/types/mydecimal.go:1306
github.com/pingcap/tidb/executor/aggfuncs.(*avgOriginal4DistinctDecimal).UpdatePartialResult
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/executor/aggfuncs/func_avg.go:228
github.com/pingcap/tidb/executor.(*HashAggExec).execute
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/executor/aggregate.go:930
github.com/pingcap/tidb/executor.(*HashAggExec).unparallelExec
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/executor/aggregate.go:858
github.com/pingcap/tidb/executor.(*HashAggExec).Next
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/executor/aggregate.go:711
github.com/pingcap/tidb/executor.Next
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/executor/executor.go:280
github.com/pingcap/tidb/executor.(*SelectionExec).Next
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/executor/executor.go:1272
github.com/pingcap/tidb/executor.Next
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/executor/executor.go:280
github.com/pingcap/tidb/executor.(*ProjectionExec).unParallelExecute
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/executor/projection.go:193
github.com/pingcap/tidb/executor.(*ProjectionExec).Next
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/executor/projection.go:179
github.com/pingcap/tidb/executor.Next
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/executor/executor.go:280
github.com/pingcap/tidb/executor.(*recordSet).Next
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/executor/adapter.go:142
github.com/pingcap/tidb/server.(*tidbResultSet).Next
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/server/driver_tidb.go:304
github.com/pingcap/tidb/server.(*clientConn).writeChunks
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/server/conn.go:1881
github.com/pingcap/tidb/server.(*clientConn).writeResultset
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/server/conn.go:1829
github.com/pingcap/tidb/server.(*clientConn).handleStmt
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/server/conn.go:1723
github.com/pingcap/tidb/server.(*clientConn).handleQuery
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/server/conn.go:1569
github.com/pingcap/tidb/server.(*clientConn).dispatch
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/server/conn.go:1103
github.com/pingcap/tidb/server.(*clientConn).Run
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/server/conn.go:861
github.com/pingcap/tidb/server.(*Server).onConn
\t/home/jenkins/agent/workspace/tidb_master/go/src/github.com/pingcap/tidb/server/server.go:481
runtime.goexit
\t/usr/local/go/src/runtime/asm_amd64.s:1357

4. What is your TiDB version? (Required)

Release Version: v4.0.0-beta.2-2807-g289dcfefd-dirty
Edition: Community
Git Commit Hash: 289dcfe
Git Branch: master
UTC Build Time: 2021-05-06 15:11:16
GoVersion: go1.13
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false

[ichn-hu]

@aytrack this should be a planner's bug, and note also cascades_planner is not GAed yet, so I doubt if this bug should be a major bug.

[aytrack]

I will change the sig label to planner, but I think it's a major bug because the TiDB was panic.

[blacktear23]

Seems planner missing a Projection between HashAgg_18 and TableReader_19

[zoomxi]

/assign