add global system variable and session variable account isolation cases

[heni02]

User description

What type of PR is this?

• API-change
• BUG
• Improvement
• Documentation
• Feature
• Test and CI
• Code Refactoring

Which issue(s) this PR fixes:

issue #16047

What this PR does / why we need it:

add global system variable and session variable account isolation cases

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PR Type

Tests

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Description

• Added new test cases to verify the setting and isolation of global system variables.
• Added new test cases to verify the setting and isolation of session variables.
• Created SQL scripts to automate the testing of these variables across different accounts.

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Changes walkthrough 📝

Relevant files

Tests

system_variables_new.result Add test cases for global and session system variables      test/distributed/cases/database/system_variables_new.result Added test cases for setting and verifying global system variables. Added test cases for setting and verifying session variables. Included checks for variable isolation across different accounts. +352/-0  system_variables_new.sql Add SQL scripts for testing system variable isolation        test/distributed/cases/database/system_variables_new.sql Created accounts for testing variable settings. Added SQL commands to set and verify global system variables. Added SQL commands to set and verify session variables. Included SQL commands to confirm variable isolation across different accounts. +161/-0

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PR Review 🔍

⏱️ Estimated effort to review [1-5]	4, because the PR involves a significant number of new test cases and SQL commands that need to be thoroughly reviewed for syntax, logic, and potential side effects in different session and global settings. The complexity of the variable settings and their interactions across different accounts increases the review effort.
🧪 Relevant tests	Yes
⚡ Possible issues	Possible Bug: The test cases show some internal errors when setting session variables that are actually global. This might be intentional to test error handling, but it should be clearly documented to avoid confusion.
	Inconsistency: There are discrepancies in the expected values of some variables (e.g., max_connections, lower_case_table_names) after setting them, which might indicate either an issue with the test setup or the database system's variable handling.
🔒 Security concerns	No

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PR Code Suggestions ✨

Category	Suggestion	Score
Possible issue	Add checks to ensure accounts do not already exist before creating them Consider adding a check to ensure that the accounts acc1, acc2, and acc3 do not already exist before attempting to create them. This will prevent potential errors if the accounts already exist. test/distributed/cases/database/system_variables_new.sql [2-4] +drop account if exists acc1; +drop account if exists acc2; +drop account if exists acc3; create account acc1 ADMIN_NAME 'admin' IDENTIFIED BY '111'; create account acc2 ADMIN_NAME 'admin' IDENTIFIED BY '111'; create account acc3 ADMIN_NAME 'admin' IDENTIFIED BY '111'; Suggestion importance[1-10]: 8 Why: Adding checks for the existence of accounts before creating them is crucial to prevent errors and ensure the script's robustness.	8
	Add a check to ensure max_connections is set correctly after attempting to change it Add a check to ensure that the global variable max_connections is set correctly after attempting to set it to 65536, as the subsequent select shows it remains 151. test/distributed/cases/database/system_variables_new.sql [19-20] set global max_connections=65536; select @@max_connections; +-- Check if the value is set correctly +if @@max_connections != 65536 then + signal sqlstate '45000' set message_text = 'Failed to set max_connections to 65536'; +end if; Suggestion importance[1-10]: 6 Why: Adding a check for the correct setting of max_connections is important for validating the expected behavior of the system configuration.	6
Best practice	Reset global variables to their default values at the end of the test To ensure consistency and avoid potential conflicts, consider resetting the global variables to their default values at the end of the test. test/distributed/cases/database/system_variables_new.sql [159-161] +set global sql_mode = "DEFAULT"; +set global TIME_ZONE = "SYSTEM"; +set global autocommit = on; +set global enable_privilege_cache = on; +set global save_query_result = off; +set global max_connections = 151; +set global lower_case_table_names = 1; +set global keep_user_target_list_in_result = 1; +set global interactive_timeout = 28800; +set global net_write_timeout = 60; +set global wait_timeout = 28800; +set global sql_select_limit = 18446744073709551615; +set global max_allowed_packet = 67108864; +set global tx_isolation = "REPEATABLE-READ"; drop account acc1; drop account acc2; drop account acc3; Suggestion importance[1-10]: 7 Why: Resetting global variables to their default values at the end of the test is a best practice to avoid side effects on other tests or systems.	7
Robustness	Add error handling for setting session variables that are actually global Consider adding error handling for setting session variables that are actually global, to make the test more robust and informative. test/distributed/cases/database/system_variables_new.sql [80-81] set max_connections=1000; +if @@error then + signal sqlstate '45000' set message_text = 'Failed to set max_connections as it is a global variable'; +end if; select @@max_connections; Suggestion importance[1-10]: 6 Why: Adding error handling for incorrect scope variable settings increases the robustness and clarity of the test script.	6