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I hava an ArrayList that got filled from an SQL query and contains all the rows of a table.
If I want a subset of this ArrayList (say WHERE column1 = x)
Is it faster to remake an SQL connection and fetch a query with this condition, or loop through the arraylist and filter the data ? (considering an arraylist of 1000 rows)
If the loop through the arraylist is faster, until what size is it still appliable ?
Thank you
It should be always faster to do this in Java. Java filtering of a memory array is as fast as, or faster, than SQL. And you also have to consider the overhead of connecting to the database, sending the command, and decoding the answer.
For really complex queries it could be simpler to have this done by SQL, and it probably scales better regarding to database size (think one million rows: are you going to keep them all in memory?). Also, the SQL query optimizer might have more information on column cardinality and be able to perform more efficiently, and therefore faster, overall, than your merely-faster-on-a-check-by-check-basis Java code.
On the other hand, also consider maintainability of the code. Some things are better left to SQL even if they’re a mite slower that way.