Disable sql query cache in debug mode

[andrepereiradasilva]

Pull Request for Issue #13265.

Summary of Changes

This PR makes the query cache disabled when db driver runs in debug mode.
Only for mysql, because the profiling only seems to work there.

Also add checks for profiling in pdomysql (was missing), which meand pdo mysql driver now as the "Profile" in debug console too.

Testing Instructions

1. Apply patch
2. Enable debug mode in global config and system debug plugin
3. Test Mysql, MySqli and PDO Mysql drivers: Reload the pages and confirm in debug console "Database Queries" "Profile" that each query in run without using db cache

Example

With query cache

Without query cache

Documentation Changes Required

None.

Notes

• Didn't test "mysql" driver because is not available in my test server (only "mysqli" and "pdo (mysql)")
• before merging, this should be reviewed from a expert db person.
• More info http://dev.mysql.com/doc/refman/5.7/en/query-cache-configuration.html

[csthomas]

There is also option DEMAND which may add some flexibility.
http://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_query_cache_type
https://mariadb.com/kb/en/mariadb/server-system-variables/#query_cache_type

I do not know if anybody care but for mysql driver missing line:
mysql_query($this->connection, 'SET profiling_history_size = 100;');

[andrepereiradasilva]

Yeah i noticed that too. Didn't add it because i have no MySQL drivers to test. If anyone confirms it works i can add it.

[csthomas]

IMHO It does not depend on type of driver like mysql or mysqli or pdomysql.
http://stackoverflow.com/questions/8443674/profiling-and-optimising-php-mysql-websites

[andrepereiradasilva]

ok added to mysql too, but his needs to be tested in mysql also

[csthomas]

I have tested this item ✅ successfully on eecd48e

Code review + I have tested it before and after patch on mysql, mysqli and pdomysql with successful.
On debug mode is now with out checking query cache.

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[waader]

Profil comes with this message: "No SHOW PROFILE (maybe because there are more than 100 queries)"
But I have only 26 queries logged. The system plugin is enabled with each option set to yes.

Does somebody know what´s going on here?

[brianteeman]

The query cache is deprecated as of MySQL 5.7.20, and is removed in MySQL 8.0.

as of MySQL 5.6.8 query cache is now disabled by default
source https://dev.mysql.com/doc/refman/5.7/en/query-cache-configuration.html

[csthomas]

@brianteeman Is there any rule? How to become a new owner?

[mbabker]

Fork the source branch of the PR, make your changes, and open a new PR.

[brianteeman]

@csthomas will you be able to take over this?

[csthomas]

I created a new PR #20322.

[joomla-cms-bot]

Set to "closed" on behalf of @franz-wohlkoenig by The JTracker Application at issues.joomla.org/joomla-cms/13268

[ghost]

closed in favor of PR #20322 as stated above.

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