statistics: update some vars for internal sessions correctly (#53977)

[ti-chi-bot]

This is an automated cherry-pick of #53977

What problem does this PR solve?

Issue Number: close #53972

Problem Summary:

What changed and how does it work?

We need to always update these vars for internal sessions. Otherwise, it won't work. And we will use the wrong default value.

See more at the issue.

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.

修复 tidb_analyze_partition_concurrency 在自动分析无法生效的问题
Fix tidb_analyze_partition_concurrency not working in auto-analysis

[fixdb]

@hi-rustin Do we really need it for 7.1?

[Rustin170506]

Tesed locally:
Before change:

[2024/11/11 17:15:45.239 +08:00] [INFO] [analyze.go:288] ["analyze partition concurrency"] [concurrency=0]

After change:

[2024/11/11 17:26:16.875 +08:00] [INFO] [analyze.go:295] ["analyze partition concurrency"] [concurrency=1]

Test step:

1. Start the cluster: tiup playground v7.1.0 --db.binpath /Users/rustin/code/tidb/bin/tidb-server
2. Print the var

	logutil.BgLogger().Info("analyze partition concurrency", zap.Int("concurrency", partitionStatsConcurrency))

3. Insert data and set the var:

SET @@global.tidb_analyze_partition_concurrency = 4;
CREATE TABLE test.my_table (
    id INT PRIMARY KEY,
    name VARCHAR(255),
    value INT,
    big_number BIGINT,
    INDEX idx_big_number (big_number)
);

INSERT INTO test.my_table (id, name, value, big_number)
WITH RECURSIVE numbers AS (
    SELECT 1 as n
    UNION ALL
    SELECT n + 1 FROM numbers WHERE n < 1000
)
SELECT
    n as id,
    CONCAT('Name_', n) as name,
    FLOOR(RAND() * 1000) as value,
    n * 1000000000 + FLOOR(RAND() * 1000000000) as big_number
FROM numbers;
SELECT @@global.tidb_analyze_partition_concurrency;

4. Check the log

[2024/11/11 17:51:57.280 +08:00] [INFO] [analyze.go:298] ["analyze partition concurrency"] [concurrency=4]

[Rustin170506]

7.1 doesn't have tidb_enable_async_merge_global_stats.

[Rustin170506]

/retest

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AilinKid, Rustin170506

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-11-11 09:46:10.34308131 +0000 UTC m=+263132.533950305: ☑️ agreed by Rustin170506.
• 2024-11-11 09:51:43.415152836 +0000 UTC m=+263465.606021831: ☑️ agreed by AilinKid.

[Rustin170506]

/retest

[codecov]

Codecov Report

Attention: Patch coverage is 45.45455% with 6 lines in your changes missing coverage. Please review.

Please upload report for BASE (release-7.1@8003f50). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.1     #53986   +/-   ##
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