*: adapt the show columns, show index and rename for column privilege

[CbcWestwolf]

What problem does this PR solve?

Issue Number: ref #61706

Problem Summary:

What changed and how does it work?

Adapt the show columns, show index and rename for column privilege
This PR pick pkg/executor/show.go, pkg/executor/simple.go, pkg/parser/auth/auth.go, tests/integrationtest/t/executor/show.test and tests/integrationtest/r/executor/show.result in #61638

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.

None

[codecov]

Codecov Report

Attention: Patch coverage is 81.57895% with 7 lines in your changes missing coverage. Please review.

Please upload report for BASE (release-8.5-20250606-v8.5.2@f43a133). Learn more about missing BASE report.

Additional details and impacted files

@@                       Coverage Diff                        @@
##             release-8.5-20250606-v8.5.2     #61679   +/-   ##
================================================================
  Coverage                               ?   57.0151%           
================================================================
  Files                                  ?       1770           
  Lines                                  ?     629075           
  Branches                               ?          0           
================================================================
  Hits                                   ?     358668           
  Misses                                 ?     246281           
  Partials                               ?      24126           

Flag	Coverage Δ
integration	36.8581% <65.7894%> (?)
unit	72.6709% <71.0526%> (?)

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

Components	Coverage Δ
dumpling	52.9278% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	52.3308% <0.0000%> (?)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[CbcWestwolf]

/retest

[CbcWestwolf]

/retest

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign bornchanger for approval. For more information see the Code Review Process.
Please ensure that each of them provides their approval before proceeding.

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

Needs approval from an approver in each of these files:

• OWNERS
• pkg/parser/OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[Copilot]

Pull Request Overview

This PR adapts the behavior of the "show columns", "show index", and "rename" functionalities to properly enforce column-specific privileges. It updates integration tests, error expectations, privilege checking logic in executor code, and refactors user/host retrieval in the authentication module.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/integrationtest/t/executor/show.test	Adds integration tests for column and index privilege enforcement.
tests/integrationtest/r/executor/show.result	Updates expected outputs for the new privilege behaviors.
pkg/parser/auth/auth.go	Introduces GetUserAndHostName for consistent user/host extraction.
pkg/executor/simple.go	Renames user privileges in the mysql.columns_priv table.
pkg/executor/show.go	Implements column-level privilege checks for SHOW queries.

[Copilot]

[nitpick] The connection command contains a double comma which may indicate an empty parameter (such as an empty password). Consider adding a clarifying comment if this is intentional to improve readability.

Suggested change

	connect (test_show_columns_user, localhost, test_show_columns_user,,);
	connect (test_show_columns_user, localhost, test_show_columns_user,,); -- The double comma indicates an empty password for the connection.

[Copilot]

[nitpick] Clarify via an inline comment that when table-level privileges are not granted, the code proceeds to check each column for specific privileges, with passColPrivCheck set when at least one column passes. This will help future maintainers understand the dual privilege check logic.

Suggested change

	}
	}
	// If table-level privileges are not granted, proceed to check column-level privileges.
	// Set passColPrivCheck to true if at least one column passes the privilege check.