Oftentimes, you can make such queries run faster by working around the distinct by using a group by instead: select my_table.foo from my_table where [whatever where conditions you want] group by foo;
Things that can cause a delete to be slow: deleting a lot of records many indexes missing indexes on foreign keys in child tables. (thank you to @CesarAlvaradoDiaz for mentioning this in the comments) deadlocks and blocking triggers cascade delete (those ten parent records you are deleting could mean millions of child records getting deleted) … Read more