What is the main disadvantage of indexes? Why can't we just cover the entire table with indexes?

The main downside of indexes is the additional resource consumption when data is modified. Each index requires disk space and memory, and also slows down insert, update, and delete operations because indexes need to be maintained in an up-to-date state.

You cannot simply cover the entire table with indexes because:

• It will significantly increase the space used.
• The performance of write operations will decrease considerably.
• Redundant indexes can lead to degraded query performance due to the selection of inefficient execution plans.

Indexes should be created consciously, based on actual queries and load.