Problem with adding new field

no, you dont understand me.

I changed storage engine from MyISAM to InnoDB for all _comprofiler tables, thats alright, but i still cant add new field in joomla.

But when I click on operation tab in phpmyadmin, its shows me a warning:

PhpMyAdmin configuration storage has been deactivated.

But i am not sure, what it means.

I ask my host provider if mysql database is running correctly, because in status is, that mysql server is running just a 5 days, but my web has two months, so maybe he made any restart or sometnihg else? I will write back.

For now very thanks.

Ensure debug mode and maximum error reporting are both configured within Joomla global configuration. Once done try to create a new field and see if the error provides any further information. It's not providing a callstack or what part of the query is erroring specifically so I don't know what to tell you.

maybe this will better?

I see no issues in the source code where the error is coming from. The error doesn't make much sense either as there's absolutely nothing wrong with the query. Try running the alter table query after "SQL=" directly on your database using phpmyadmin or whatever database management software your host provides.

Is this what you think?

Ok, you are indeed hitting column size limits. Are you sure _comprofiler is changed to InnoDB engine? Click the _comprofiler table in your table list. Then click "Operations" and change the "Storage Engine" to "InnoDB".