ddl_notifier: implement serialization and deserialization for SchemaChangeEvent

[fzzf678]

What problem does this PR solve?

Issue Number: ref #55722

Problem Summary:

What changed and how does it work?

Add Marshal and UnMarshal method for SchemaChangeEvent.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

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

[tiprow]

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[codecov]

Codecov Report

Attention: Patch coverage is 93.60000% with 8 lines in your changes missing coverage. Please review.

Project coverage is 56.7927%. Comparing base (b9a7d35) to head (be7d271).
Report is 15 commits behind head on master.

Additional details and impacted files

@@                Coverage Diff                @@
##             master     #56089         +/-   ##
=================================================
- Coverage   72.8966%   56.7927%   -16.1040%     
=================================================
  Files          1609       1762        +153     
  Lines        447141     635609     +188468     
=================================================
+ Hits         325951     360980      +35029     
- Misses       101132     249795     +148663     
- Partials      20058      24834       +4776     

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unit	72.0719% <92.0000%> (+0.0641%)	⬆️

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Components	Coverage Δ
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parser	∅ <ø> (∅)
br	63.0302% <ø> (+17.2388%)	⬆️

[lance6716]

What's the reason to change the column type?

[fzzf678]

I tried the JSON type and use row.GetJSON() and row.GetBytes() get the serialized data, but it can't be deserialized. I took a look at other system tables like tidb_global_task and tidb_background_subtask, they use LONGBLOB type save the meta and row.GetBytes() get the serialized data and I did so. Is it my way of operating the JSON type is wrong?

[lance6716]

diff --git a/pkg/ddl/notifier/publish_testkit_test.go b/pkg/ddl/notifier/publish_testkit_test.go
index 30f0c1170f..d5e01cbabf 100644
--- a/pkg/ddl/notifier/publish_testkit_test.go
+++ b/pkg/ddl/notifier/publish_testkit_test.go
@@ -35,7 +35,7 @@ func TestPublishToTableStore(t *testing.T) {
 CREATE TABLE ddl_notifier (
        ddl_job_id BIGINT,
        multi_schema_change_seq BIGINT COMMENT '-1 if the schema change does not belong to a multi-schema change DDL. 0 or positive numbers representing the sub-job index of a multi-schema change DDL',
-       schema_change LONGBLOB COMMENT 'SchemaChange at rest',
+       schema_change JSON COMMENT 'SchemaChange at rest',
        processed_by_flag BIGINT UNSIGNED DEFAULT 0 COMMENT 'flag to mark which subscriber has processed the event',
        PRIMARY KEY(ddl_job_id, multi_schema_change_seq)
 )
diff --git a/pkg/ddl/notifier/store.go b/pkg/ddl/notifier/store.go
index c652fd0052..f259277e0b 100644
--- a/pkg/ddl/notifier/store.go
+++ b/pkg/ddl/notifier/store.go
@@ -94,7 +94,12 @@ func (t *tableStore) List(ctx context.Context, se *sess.Session, limit int) ([]*
        ret := make([]*schemaChange, 0, len(rows))
        for _, row := range rows {
                event := SchemaChangeEvent{}
-               err = json.Unmarshal(row.GetBytes(2), &event)
+               binaryJSON := row.GetJSON(2)
+               jsonStr, err := binaryJSON.MarshalJSON()
+               if err != nil {
+                       return nil, errors.Trace(err)
+               }
+               err = json.Unmarshal(jsonStr, &event)
                if err != nil {
                        return nil, errors.Trace(err)
                }

However I don't have strong opinion about the column type. JSON type can add JSON syntax check in the SQL layer and readable SELECT output, LONGTEXT or LONGBLOB has readable SELECT output. LONGBLOB has no advantage. Maybe wait other reviewers' opinions.

[fzzf678]

I tried again and found that the JSON type in table is not equal to our internal json type in code, we need a conversion to use the JSON type in table like this:

j, err := row.GetJSON(2).MarshalJSON()
err = json.Unmarshal(j, &event)

https://github.com/pingcap/tidb/blob/master/pkg/types/json_binary.go#L151-L180

[lance6716]

rest lgtm

[lance6716]

Because other reviewers and me has no comment, I think you can choose the type as you like. Please /unhold after you choose it.

[lance6716]

/hold

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: CbcWestwolf, lance6716

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-09-18 03:46:04.802907408 +0000 UTC m=+1019234.543331347: ☑️ agreed by CbcWestwolf.
• 2024-09-18 06:24:21.987593871 +0000 UTC m=+1028731.728017810: ☑️ agreed by lance6716.

[fzzf678]

/retest

[fzzf678]

/unhold

[tiprow]

@fzzf678: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest

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