Also important thing to note is that optimal query plan can be different based on the data you have. To get a good performance you will chose a different strat

Also important thing to note is that optimal query plan can be different based on the data you have. To get a good performance you will chose a different strategy when your query has 3 jorges out 1M records vs if you have 900k jorges in 1M records or when the table only contains 100 entries. Why indexes are not always a good idea? To use an index you need to make at least two lookups per entry, one for index and one to fetch the data. If your query will fetch 900k rows out of 1m rows table, much faster is just to read the data and just filter out values we are not interested in.