privilege, domain: reduce the memory jitter of privilege reload activity for 2M users

[tiancaiamao]

What problem does this PR solve?

Issue Number: close #59403, ref #55563

Problem Summary:

I create 2M users, and for example, make 10% or 50% of the users active (in-memory).

Then I observe that even when the workload is gone, the tidb-server memory usage jitter periodically.
For example, this one:

What changed and how does it work?

There are several changes.

1. Before this PR, loadAll() is used when the active user count > 1024 ... that's the direct root cause of the jitter.

That's because loadSomeUsers() does not support tooooo many filter condition.
The SQL "select * from user where user = 'a' or user = 'b' or user = 'c' or ..." works poorly when there are too many or conditions. This is a known issue #43885 that we write the code the recursive way and cause stackoverflow.

So the first change is to enhance loadSomeUsers() to support unlimited user count.

It works like this:

• if user count > 1024, use the 'or user = xx' filter condition to construct the SQL
• otherwise, use load all SQL but do the 'user = xx' filter condition in the user space.

2. Use this SQLExecutor.ExecuteInternal() streaming API to replace RestrictedSQLExec.ExecRestrictedSQL() API

The problem of ExecRestrictedSQL is that the API design not fit here.
Its drainRecordSet return []chunk.Row as result and here it can be 2M huge array.
What we need is a streaming API, doing the filter condition at the same time rather than take the whole data set and filter out later.

3. Use deep copy in the loadTable decode function.

I suspect there is a leak like #59403, the decode function may using a shallow copy and it references the chunk data.
So the whole chunk cannot be freed.

Check List

Tests

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

The memory usage now:

The privilege reload activity is every 10min and you can see that the max memory usage is much less than before:

• 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

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[tiancaiamao]

/test pull-br-integration-test

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[tiancaiamao]

/retest

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[tiancaiamao]

/unhold

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-02-15 09:25:24.867288698 +0000 UTC m=+694167.263510785: ☑️ agreed by CbcWestwolf.
• 2025-02-25 05:54:27.451768251 +0000 UTC m=+335215.404926517: ☑️ agreed by lcwangchao.

[tiancaiamao]

/test check-dev2

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[tiancaiamao]

/test check-dev2

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[tiancaiamao]

/test check-dev2

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[lance6716]

/approve

for domain part

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[APPROVALNOTIFIER] This PR is APPROVED

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

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #59812.
But this PR has conflicts, please resolve them!