I create a table on an empty database. Table is called Detail, has 4 columns with first one as a primary key:
I insert a single record and display column info:
There is PRI in KEY column of idDetail (as it should be). I then create a trigger on INSERT and display column info again:
No change, PRI is still where it should be. I then execute an update on a single and only row. Update should neither activate the trigger, nor actually change anything (since the value in the row is the same as in the update).
After update I display column info once again:
Suddenly PRI is missing from KEY column. I execute the very same update again and then show columns again.
PRI is back in the KEY column. If I then again execute update, PRI is gone, and then after another one is back. Same behaviour when I execute INSERT.
I then DROP the trigger, update the record and show columns again twice :
After the trigger is dropped, SHOW columns always correctly lists PRI in Key column for idDetail.
Ubuntu 15.10, Brfs filesystem, InnoDB (XtraDB), single database server, no replication, root access, all commands entered separately through the command line (bash) after logging through mysql command