Pull Request for Issue # .

Summary of Changes

This PR fixes all datetime columns of the #__redirect_links database table so there will not be any Invalid value '0000-00-00 00:00:00' for datetime error anymore on MySQL 5.7 or later when strict mode is enabled.

In opposite to PR #26372 , this PR here does not depend on PR #26295 , because this one here does not have anything to change in table #__ucm_content.

Currently the #__redirect_links table only contains 2 datetime columns, created_date and modified_date. Those will be handled like the same columns of the #__banners table in PR #26372 , i.e. they will get no default value.

The default value is only used when inserting new records without specifying values for that particular column. Not having a default will enforce to insert new records with values for these columns being provided and throw an SQL error if some of these values is not specified, i.e. such errors will not be hidden anymore.

Old data will be updated as little as possible. The created_date column will be not touched at all. We can assume that for core components there is no data with values '0000-00-00 00:00:00' on MySQL or '1970-01-01 00:00:00' on PostgreSQL, and data created by 3rd party components should not be modified. The modified_date column will be set to the value of the created_date column only on MySQL if it has value '0000-00-00 00:00:00'. Our PHP already sets the modified time to the created time when saving new records, i.e. modified = created means never modified. On PosgreSQL we do not need to update the modified column because there is no invalid datetime value '0000-00-00 00:00:00' problem.

Testing Instructions

Testers please report back the database kind (MySQL or PostgreSQL) on which you have tested.

If you have both MySQL and PostgreSQL, please test on both if possible.

Test 1: New installation

1. Apply the patch on a clean 4.0-dev branch using git or merging manually, or apply it on an installation of current 4.0-dev using patchtester.
2. If used patchtester on an existing installation in step 1, delete file configuration.php and delete all Joomla database tables in PhpMyAdmin or PhpPgAdmin (depending on your database type).
3. Do a new installation, login to backend, confirm the statistics dialog, go to global config and set error reporting to maximum or development in server settings.
4. Play around with com_redirect, create some links, modify some, ...
5. After any action, check in your database the relevant datetime/timestamp without timezone columns.

Result: See section "Expected result" below.

Test 2: Update sql script

1. Install a clean clean 4.0-dev, login to backend, confirm the statistics dialog, go to global config and set error reporting to maximum or development in server settings.
2. Apply the changes from this PR e.g. manually or with patch tester.
3. Open PhpMyAdmin or PhpPgAdmin (depending on your database type), select your database and then go to the SQL command input.
4. On MySQL copy the first line of file installation/sql/mysql/joomla.sql into the SQL command window but don't execute the commands yet:

SET SQL_MODE = "NO_AUTO_VALUE_ON_ZERO";

This switches off strict mode to the SQL will run on MySQL 5.7 or later.

5. Copy the content of file administrator/components/com_admin/sql/updates/mysql/4.0.0-2019-09-23.sql or administrator/components/com_admin/sql/updates/postgresql/4.0.0-2019-09-23.sql (depending on your database type) into the SQL command window, in case of MySQL below the previously pasted commands, but don't execute the commands yet.
6. Replace #__ by your database prefix in the SQL statements pasted before in the SQL input window.
7. Put the cursor to the beginning of the 1st SQL statement in the SQL input window and now execute all SQL commands.
8. Play around with com_redirect, create some links, modify some, ...
9. After any action, check in your database the relevant datetime/timestamp without timezone columns.

Result: See section "Expected result" below.

Expected result

The Redirect component works as well as before. In database there are no columns of type datetime having value '0000-00-00 00:00:00' in a MySQL database, and there is no invalid default value anymore in MySQL >= 5.7 with strict mode on in that kind of database.

Actual result

The Redirect component works. In a MySQL database there might be columns of type datetime having value '0000-00-00 00:00:00', and the default value of these database columns is invalid in MySQL >= 5.7 with strict mode on.

Documentation Changes Required

Maybe core developer docs and extension developer docs should be updated to encourage them not to use '0000-00-00 00:00:00' on MySQL anymore but use real NULL and not abuse '1970-01-01 00:00:00' on PostgreSQL as a speudo null date anymore and use real NULL values also there.