fix: close issue 59446 make oct("") same as mysql

[yihong0618]

What problem does this PR solve?

• [ ] Unit test
• [x] 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

[ti-chi-bot[bot]]

Hi @yihong0618. Thanks for your PR.

I'm waiting for a pingcap member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[tiprow[bot]]

Hi @yihong0618. Thanks for your PR.

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[yihong0618]

/ok-to-test

[ti-chi-bot[bot]]

@yihong0618: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/ok-to-test

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[tiprow[bot]]

@yihong0618: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/ok-to-test

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[lance6716]

/ok-to-test

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 73.0014%. Comparing base (e8aa60d) to head (5cdb301). Report is 176 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #61767        +/-   ##
================================================
- Coverage   73.0655%   73.0014%   -0.0642%     
================================================
  Files          1730       1756        +26     
  Lines        481483     511171     +29688     
================================================
+ Hits         351798     373162     +21364     
- Misses       108134     115965      +7831     
- Partials      21551      22044       +493     

Flag	Coverage Δ
integration	42.3355% <100.0000%> (?)
unit	72.1757% <14.2857%> (-0.1307%)	:arrow_down:

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	52.6673% <ø> (-0.1132%)	:arrow_down:
parser	∅ <ø> (∅)
br	44.6952% <ø> (-1.9919%)	:arrow_down:

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[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2025-06-20 05:08:29.407539656 +0000 UTC m=+421162.130718637: :ballot_box_with_check: agreed by lance6716.
• 2025-06-23 08:51:33.495460717 +0000 UTC m=+693746.218639699: :ballot_box_with_check: agreed by YangKeao.

[lance6716]

/assign @zanmato1984

[hawkingrei]

/retest

[yihong0618]

Thank you @yihong0618 for contributing! This change looks good. However generally we want to update the vectorized version as well: https://github.com/pingcap/tidb/blob/6e13f827fcd924c8c791d327c7148b4377285d6e/pkg/expression/builtin_string_vec.go#L1760

Would you mind to do that as well?

of course but for now I am on vacation will fix it this weekend

[lance6716]

ping @yihong0618

[yihong0618]

ping @yihong0618

pong, foud it used append('0') in vector here

so I thought it maybe right, but still try to full understand it

https://github.com/pingcap/tidb/blob/6e13f827fcd924c8c791d327c7148b4377285d6e/pkg/expression/builtin_string_vec.go#L1781

will fix it later

[yihong0618]

ping @yihong0618

pong and address

[lance6716]

ping @zanmato1984

[yihong0618]

addressed comments

[tiprow[bot]]

@yihong0618: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
tidb_parser_test	5cdb30172ba0f547c48edbd428aa287814ffe0aa	link	true	/test tidb_parser_test
fast_test_tiprow	5cdb30172ba0f547c48edbd428aa287814ffe0aa	link	true	/test fast_test_tiprow

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[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lance6716, YangKeao, zanmato1984

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Needs approval from an approver in each of these files:

• ~~OWNERS~~ [YangKeao,lance6716,zanmato1984]
• ~~pkg/expression/OWNERS~~ [zanmato1984]

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[zanmato1984]

Thank you @yihong0618 for your contribution!