does indexing tables have a bad effect on drupal? I have one or two views which has a lot of fields to show and all of this fields are in filter criteria as exposed filter. now the problem is acting in low speed.

the solution I am now thinking about is to index some fields which are more in use as filter criteria. But I don't know if it has any bad effect on performance or not. Or does it effect views automatically or I should rebuild all views to see the indexing result.

please let me know more about indexing tables in drupal or if you know any better solution let me know!
The gains far outweigh any drawbacks; I'd add the index.