CODEWITHSUNDEEP
javaoracle-databasejdbc
hershey92
hershey92

Reputation: 773

Iterating a ResultSet using the JDBC for Oracle takes a lot of time about 16s?

while( result_set.next() )
{
  ...
}

I have use System.nanoTime() and calculated the time, for each iteration the time taken is in milliseconds but the overall loop takes about 16s. I am considering a possible reason that the condition test is taking a lot of time, the next() function.

FYI I am connecting to a remote database server and the select query that I make is completed in milliseconds again calculated using the above mentioned method. Any reasons about why it's happening and how I can bring the time to iterate the resultset down to at max a second?

EDIT:

I am dealing with about 4000 records and each record contians about 10 columns each having a size of about 10 chars

EDIT2 Thanks setFetchsize() did the magic, awesome, awesome

Upvotes: 18

Views: 15698

Answers (2)

Andreas Fester
Andreas Fester

Reputation: 36630

I have set up a table with 4000 rows and 10 columns with 10 characters each and made a simple performance test using the following approach (RealTimeCounter is a class which measures the real time between start() and stop()):

List<String> myResult = new ArrayList<>();
ResultSet rs = s.executeQuery("SELECT * FROM Performance");

RealTimeCounter rtc = new RealTimeCounter();
rtc.start();
while(rs.next()) {
    myResult.add(rs.getString(1));
}
rtc.stop();
System.out.println(rtc);

Results:

  • Default fetch size: execution time is approx. 20 sec
  • fetch size = 100: execution time is approx 2.2 sec
  • fetch size = 500: execution time is approx 450 msec
  • fetch size = 2000: execution time is approx 120 msec
  • fetch size = 4000: execution time is approx 50 msec
  • fetch size = 4001: execution time is approx 10 msec (!!)

So, the fetch size does have a significant impact on the execution speed.

Note that, on the other hand, the fetch size has some impact on memory consumption. Interestingly enough, a quick analysis using Runtime.getRuntime().freeMemory(); before and after the above code showed that the impact is much less than I would expect, though. The numbers I got are:

  • Default fetch size: 665k
  • fetch size = 100: 665k
  • fetch size = 500: 665k
  • fetch size = 2000: 743k
  • fetch size = 4000: 821k
  • fetch size = 4001: 861k

Upvotes: 35

Evgeniy Dorofeev
Evgeniy Dorofeev

Reputation: 136002

Try to change ResultSet fetch size. By default, Oracle JDBC driver receives the result set only 10 rows at a time from the database cursor. It may not significantly improve performance but there arent many other options to make driver work faster.

Upvotes: 27

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