ddl: reuse chunk for copr-read and check context done

[tangenta]

What problem does this PR solve?

Issue Number: close #39468, close #39470

Problem Summary:

For #39468, when ADMIN CANCEL DDL JOBS is executed, the context is cancelled. However, the cop-request senders does not aware of this and keep sending to the results channel. As a result, WaitGroup.Wait() blocks forever because the cop-request senders never exit.

For #39470, I found that the chunk introduced in #39382 is never reused and the runtime GC worker cannot collect it because sync.Pool keeps the reference. This PR uses a different way to fix #39308: it clones everything for each datum to prevent sharing the same memory.

What is changed and how it works?

See the problem summary.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

Before this PR:

After this PR:

Before this PR:

+--------+---------+------------+------------------------+----------------------+-----------+----------+-----------+---------------------+---------------------+---------------------+---------------+
| JOB_ID | DB_NAME | TABLE_NAME | JOB_TYPE               | SCHEMA_STATE         | SCHEMA_ID | TABLE_ID | ROW_COUNT | CREATE_TIME         | START_TIME          | END_TIME            | STATE         |
+--------+---------+------------+------------------------+----------------------+-----------+----------+-----------+---------------------+---------------------+---------------------+---------------+
|     85 | sbtest  | sbtest1    | add index /* ingest */ | write reorganization |        76 |       78 |  39063370 | 2022-11-29 21:19:31 | 2022-11-29 21:19:31 | NULL                | cancelling    |
+--------+---------+------------+------------------------+----------------------+-----------+----------+-----------+---------------------+---------------------+---------------------+---------------+

After this PR:

+--------+---------+------------+------------------------+--------------+-----------+----------+-----------+---------------------+---------------------+---------------------+---------------+
| JOB_ID | DB_NAME | TABLE_NAME | JOB_TYPE               | SCHEMA_STATE | SCHEMA_ID | TABLE_ID | ROW_COUNT | CREATE_TIME         | START_TIME          | END_TIME            | STATE         |
+--------+---------+------------+------------------------+--------------+-----------+----------+-----------+---------------------+---------------------+---------------------+---------------+
|     88 | sbtest  | sbtest1    | add index /* ingest */ | none         |        76 |       78 |         0 | 2022-11-29 21:55:55 | 2022-11-29 21:55:55 | 2022-11-29 21:56:34 | rollback done |
+--------+---------+------------+------------------------+--------------+-----------+----------+-----------+---------------------+---------------------+---------------------+---------------+

ERROR 8214 (HY000) at line 2: Cancelled DDL job

• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• Benjamin2037
• hawkingrei

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[Benjamin2037]

LGTM

[hawkingrei]

it work. But we maybe have a better method to solve. We have possiblity to use pool to resue object. It can be removed from binding and set Finalizer to put into pool after use. We can try it after releasing v6.5.

[tangenta]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 8bda001

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 360f4ad

[tangenta]

/run-check_dev_2

[hawkingrei]

/run-check_dev_2

I have try to revert #39503 by #39521. But this task still fail.

[tangenta]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 9a4d264

[ti-chi-bot]

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[sre-bot]

TiDB MergeCI notify

✅ Well Done! New fixed [1] after this pr merged.

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci-tidb/integration-common-test	🔴 failed 2, success 15, total 17	1 hr 2 min	Existing failure
idc-jenkins-ci/integration-cdc-test	🔴 failed 1, success 39, total 40	25 min	Existing failure
idc-jenkins-ci-tidb/sqllogic-test-1	✅ all 26 tests passed	4 min 6 sec	Fixed
idc-jenkins-ci-tidb/common-test	🟢 all 11 tests passed	10 min	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	5 min 55 sec	Existing passed
idc-jenkins-ci-tidb/integration-ddl-test	🟢 all 6 tests passed	5 min 16 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	4 min 50 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	3 min 59 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	3 min 6 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed