Backticks in dbDelta cause warning and actually causes a query to alter all columns and indexes to run even if none have changed

[Driskell]

Backticks in a CREATE TABLE in a dbDelta call are causing the below warning, and running a query to alter all columns and indexes with backticks even if they haven't changed:
Notice: Undefined offset: 1 in /home/backuptechnology/public_html/wp-admin/includes/upgrade.php on line 1544

Seems this started a long long time ago after this was fixed:
http://core.trac.wordpress.org/ticket/8014

Seems there is a match on line 1587 of WordPress 3.3.1 wp-admin/includes/upgrade.php:

               // For every field in the table
                foreach ($tablefields as $tablefield) {
                        // If the table field exists in the field array...
                        if (array_key_exists(strtolower($tablefield->Field), $cfields)) {
                                // Get the field type from the query
                                preg_match("|".$tablefield->Field." ([^ ]*( unsigned)?)|i", $cfields[strtolower($tablefield->Field)], $matches);

The preg_match bit is what fails to match because it is looking for "fieldname" instead of "fieldname".
So this is where the warning occurs, and why it assumes the type of the field is wrong.
This means the previous patch 3 years ago probably meant when you have backticks in your CREATE TABLE, when you run dbDelta it actually runs an ALTER TABLE for every single column in the table, and then an ALTER TABLE ADD INDEX / PRIMARY for every single KEY and PRIMARY (there's more than just the above code that needs adjusting), causing duplicate key errors, but ignored. Guess it kinda works though...

Also seems during the DESCRIBE it doesn't use backticks so if someone has a table with a reserved name (stupid I know) it would break dbDelta completely, but that's me digressing I just think getting rid of the warnings for CREATE TABLES with backticks will be good.

But explains why my plugin takes a few seconds to activate hahaha. :-)

I'll provide a patch at some point this week or next unless someone has already done so.

Remove backticks when comparing fields and indexes

I can replicate the original problem. Here's the sample plugin I used to test this:

​https://gist.github.com/2151282

Just activate the plugin and look for errors. Deactivate the plugin to reset.

Definitely not new, setting version to 1.5 when dbDelta came around.

Adding ` to the list of characters to trim() might be enough, yes?

Adding ` to the trim list won't fix it because a backtick can occur in the middle of the string:

`user_ip` int(11) DEFAULT 0,

What's so complicated? Took me 10 seconds:

preg_match("|`?" . preg_quote($tablefield->Field, '|') . "`? ([^ ]*( unsigned)?)|i", $cfields[strtolower($tablefield->Field)], $matches);

This also fixes problems with tablenames that contain "special" characters, in MySQL for example foo.bar.[b-a-z] is a perfectly valid tablename, besides using non-sanitized external input is always a very bad idea.

However, this Regex is pretty fragile anyways, it can't handle multiple spaces, it can't handle tabs, it can't handle spaces between the parentheses enclosing the column length, etc... someone should really rewrite that whole stuff, it might explode by a slight sneeze.