Pull Request for #25258 (comment).

Summary of Changes

With PR #25258 meta keywords have been removed from diverse forms and views.

This is a good thing.

But the fields in database tables still exist, have a NOT NULL constraint and partly no default value, e.g. in the #__languages table.

This leads to content language not being installed when installing a language, see #25258 (comment).

Furthermore I saw fields metakey are still used by diverse sample data, so we can't just remove those columns, not yet.

So this PR removes the NOT NULL constraint from metakey columns where they are of type text, because for such columns default values are not allowed in strict mode, and adds missing default value empty string to those columns where they are of type VARCHAR, so things don't fail and stay BC.

Later when all metaky removal has been completed we can remove those columns from database tables with another PR, wherever appropriate (BC?).

Testing Instructions

Update

1. On a current 4.0-dev installation, apply the changes in the update sql script 4.0.0-2020-02-08.sql added by this PR e.g. with PhpMyAdmin or PhpPgAdmin, replacing #___ by your actual db prefix.

2. Install Persian language.
   Result: Content language created, no notice like shown in comment #25258 (comment).

3. Verify that following still works:

• Creating and editing banners and banner clients
• Creating and editing contacts
• Creating and editing articles
• Creating and editing newsfeeds
• Creating and editing tags

New installation

1. Apply PR on a clean current 4.0-dev and then make new installation.

2. to 3. Same as for update above.

Expected result

Code review/database check: All database columns for meta keywords have default value '' where they are of type VARCHAR and have no default and allow NULL values where they are of type TEXT.

Language installation test (step 2): No notice, and content language is created.

Other tests (step 3): Things work.

Actual result

Code review/database check: There are some database columns for meta keywords having a NOT NULL constraint and no default value.

Language installation test (step 2): Notice shown, and content language not created.

Other tests (step 3): Things work.

Documentation Changes Required

None.