I found out recently that there's no Moodle equivalent for the SQL syntax:
UPDATE tablename SET fieldname = fieldname+1
So I sat down and wrote a new function which I called "renumber_field" that does just that.
It gets table name, fiend name, amount, increase/decrease indicator and the usual conditions array.
I created an issue with an implementation for mysqli and it was suggested that I post it here to see if there's any need for the new functionality, so i'll be happy for any feedback
Would it be worth explaining the scenarios in which this functionality is useful. Off the top of my head, I am struggling to come up with times that I've wanted to do something like this, but if there are legitimate uses then this could be helpful.
Suppose there's a parent table with a child table (for example a discussion and a post).
The parent table has a column that holds the amount of its children. When adding or removing one or more children, that counter needs to be updated.
The only two available options (except the sql execute function) are update_record or set_field, both require a DB query to get the original value in order to update it, while telling the DB engine to simply update the field with the new offset saves at least one query and also a few lines of code.
Another example: You have a group of quizzes, each with a different duration, and you want to add, let's say, 30 minutes for each one. Instead of looping though all of them and updating each one separately you can run one query that adds the extra time for all quizzes in a given condition.
You should not update counts by doing +1 or -1 like that, for several reasons:
