What are the disadvantages of having many indices?

Question

I recently sped up a complicated query by an order of magnitude by giving SQLite a good index to work with. Results like this make me wonder if I should index a lot of other

Answer 1

Indexes use up disc space to store, and take time to create and maintain. Unused ones don't give any benefit. If there are lots of candidate indexes for a query, the query may be slowed down by having the server choose the "wrong" one for the query.

Use those factors to decide whether you need an index.

It is usually possible to create indexes which will NEVER be used - for example, and index on a (not null) field with only two possible values, is almost certainly going to be useless.

You need to explain your own application's queries to make sure that the frequently-performed ones are using sensible indexes if possible, and create no more indexes than required to do that.