lightning: remove the unnecessary offset field in the key encoding for duplicate detection

[sleepymole]

What problem does this PR solve?

Part of #29588.
Split from #30203.

Problem Summary:

The rowID that allocated by lightning is guaranteed to be unique, so we can remove the unnecessary offset field in the key encoding for duplicate detection.

What is changed and how it works?

Remove the unnecessary offset field in the key encoding for duplicate detection.

I tested about 5 million rows for TPCC's order_line schema.

CREATE TABLE `order_line` (
  `ol_o_id` int(11) NOT NULL,
  `ol_d_id` int(11) NOT NULL,
  `ol_w_id` int(11) NOT NULL,
  `ol_number` int(11) NOT NULL,
  `ol_i_id` int(11) NOT NULL,
  `ol_supply_w_id` int(11) DEFAULT NULL,
  `ol_delivery_d` datetime DEFAULT NULL,
  `ol_quantity` int(11) DEFAULT NULL,
  `ol_amount` decimal(6,2) DEFAULT NULL,
  `ol_dist_info` char(24) DEFAULT NULL,
  PRIMARY KEY (`ol_w_id`,`ol_d_id`,`ol_o_id`,`ol_number`) /*T![clustered_index] NONCLUSTERED */
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;

	index-engine	data-engine
duplicate-resolution="none"	31 M	194 M
duplicate-resolution="record"(master)	71 M	238 M
duplicate-resolution="record"(this PR)	52 M	218 M

The results show that the write amplification of the index engine and data engine is significantly reduced.

Check List

Tests

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

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• Little-Wallace
• glorv

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[sleepymole]

/component lightning

[sleepymole]

/run-integration-br-test

[sleepymole]

/cc @kennytm @glorv

[glorv]

rest LGTM

[glorv]

LGTM

[sleepymole]

@kennytm Could you please take a look? Thanks

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/12dcd01c88007d6dc7aca77da2bd021244621ed9

[sleepymole]

/run-unit-test

[Little-Wallace]

LGTM

[glorv]

/merge

[ti-chi-bot]

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

Commit hash: 3fb2f2e

[ti-chi-bot]

@gozssky: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

If the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.