cop task runtime information is wrong in the index join

[crazycs520]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

As you can see in the upper picture, The inner worker of IndexJoin_17 spend 2.89010439s to fetch data, but the child IndexReader_37(Build) only spend 1.999111ms, It must be something wrong.

The reason is the inner worker maybe use multiple IndexReader_37 executor to fetch data, but finally, TiDB only record the last executor time cost.

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

3. What did you see instead (Required)

4. What is your TiDB version? (Required)

master

[wshwsh12]

/label sig/execution

[sre-bot]

Integrity check：
component RCA symptom affect_version fix_version fields are empty
@crazycs520

[crazycs520]

/info

[ti-srebot]

Please edit this comment to complete the following information

Bug

1. Root Cause Analysis (RCA)

As the Issue description said, the inner worker maybe use multiple IndexReader_37 executor to fetch data, but finally, TiDB only records the last executor time cost.

2. Symptom

• N/A

3. All Trigger Conditions

• N/A

4. Workaround (optional)

• N/A

5. Affected versions

[v4.0.0:v4.0.6]

6. Fixed versions

v4.0.7