When creating a table I am unable to use the ExctractValue function to create a column, despite it being deterministic:
mysql> create table xml_test (xml TEXT, virt CHAR(16) AS (ExtractValue(xml, '//some/@xpath')) PERSISTENT;
ERROR 1901 (HY000): Function or expression is not allowed for column 'virt'
This was discussed several years ago on the dev list at https://email@example.com/msg03488.html where it was added to Launchpad bug 608641 (https://bugs.launchpad.net/maria/+bug/608641). Bug 608641 contains other functions as well and was quietly closed as "won't fix" in 2012 with no explanation.
I have a use where being able to create and index columns off stored XML would be very useful. I need to use xpath searches, I cannot use simple string manipulation. I would appreciate if this could be reevaluated. If it is still "won't-fix" please document why. Thank you.