What are the disadvantages if indexes are added on all columns?

I know, that it is not a good design to set too many indexes, but just for understanding the theory:

What exactly are the disadvantages if you add an index on all columns in a table in MySQL?

• Are the queries getting slower if I have indexes on columns, that i

rarely use?

• Are the inserts somewhat slower?

• Is MySQL able to pick out the best index that speeds up the query?

• Insert/Updates/Delete speed will degrade. The index has to be updated on data modification.

• I don't know mysql in fine details but it also means more time spent by the query planner to determine the indexes to use.

• More disk space.

These are the key disadvantages.

StackExchange Database Administrators Q#39966, answer score: 5