SQL（例如 mysql、postgresql）与 java8 流性能和更快？

Question

eg `

 where like '%str%' vs stream().filter(i -> i.contains(str))
    group by column a vs stream().groupingby(column_a)
    group by column_a, column_b vs stream().groupingby(column_a, groupingby(column_b))
    count vs stream().count
    sum vs stream().sum
    order by vs stream().sort

... `

I'd like to know which is faster and performance is better when it is performed in same spec server or different, thinks.

Answer 1

Those are different usecases. Database were designed to work with persisted data, streams traverse given data structures. So to use streams, you would need to read the data somehow first, that is where you use the database with indexes that helps especially with %like% .

So should the question be whether it is faster to do sum, group by, count, order by in database as part of the query or fetch the data from database and do those operations with java, then you hardly find a case where you doing it by streams would be preferable.

The database is made to be fast, streams are made to be sexy to work with. You can find stream performance related questions ( here , here , and you can find others) that shows that the streams are really slow. The streams can work in parallel to become faster, but the the database do that as well.