ddl: Remove explicit exclude for "engine" notIn "tiflash" (#58637)

[ti-chi-bot]

This is an automated cherry-pick of #58637

What problem does this PR solve?

Issue Number: close #58633

Problem Summary:

When creating a placement policy through tidb, tidb will create a placement-rule with "engine" notIn "tiflash" #22065
However, under tiflash disaggregated compute and storage arch, the compute node will register store with label {"engine": "tiflash_compute"}.

The logic in PD of choosing store for rule: pkg/schedule/placement/label_constraint.go @ pd

1. If the store's label.key is equal to "engine" (or "exclusive," or starts with '$'), and the rule's constraint does not contain a rule with the same label.key, then do not schedule the peer to this store.
2. Otherwise, further check if the rule's constraint matches the store's label. If it matches, schedule the peer to this store.

So the PD would pick tiflash compute node as target store to place the Region peer.

What changed and how does it work?

Remove the explicit exclude rule "engine" notIn "tiflash" when generating rule

Check List

Tests

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

1. Deploy a cluster with tikv and disaggregated tiflash (1 tiflash compute node and 1 tiflash storage node)
2. Load TPC-H dataset into the cluster and create tiflash replica
3. Create placement policy

CREATE PLACEMENT POLICY evict_sata_dw CONSTRAINTS="[-disk=sata-new, -disk=dw-ssd]" SURVIVAL_PREFERENCES="[host]";
ALTER TABLE test.region PLACEMENT POLICY=evict_sata_dw;
ALTER RANGE global PLACEMENT POLICY evict_sata_dw;

4. Check the cluster status, no node crashes

• 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.

Fix a bug that after executing `ALTER TABLE ... PLACEMENT POLICY ...` Region peers may be unexpectedly added to the TiFlash Compute Node in the disaggregated storage and compute architecture

[ti-chi-bot]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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Additional details and impacted files

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##             release-8.1     #59038   +/-   ##
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Flag	Coverage Δ
unit	71.2078% <100.0000%> (?)

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Components	Coverage Δ
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parser	∅ <0.0000%> (?)
br	41.3712% <0.0000%> (?)

[JaySon-Huang]

@tangenta @xhebox PTAL