Simple hash improves performance
--------------------------------
Key: DERBY-1862
URL: http://issues.apache.org/jira/browse/DERBY-1862
Project: Derby
Issue Type: Improvement
Components: Performance
Affects Versions: 10.1.3.1, 10.1.2.1
Environment: WinXp, JRE 1.5_6., Hibernate 3.1
Reporter: Tore Andre Olmheim
We are currently developing a system where we load between 1000 and 5000
objects in one go. The user can load different chunks of objects at any time as
he/she is navigating.
The system consist of a java application which accesses derby via hibernate.
During profiling we discovered that the org.apache.derby.iapi.util.StringUtil
is the biggest bottleneck in the system.
The method SQLEqualsIgnoreCase(String s1, String s2) is doing upperCase on both
s1 and s2, all the time.
By putting the uppcase value into a Hashtable and using the input-string as key
we increates the performance with about 40%.
Our test-users report that the system now seems to run at "double speed".
The class calling the StringUtil.SQLEqualsIgnoreCase in this case is
org.apache.derby.impl.jdbc.EmbedResultSet
This class should also be checked as it seems to do a lot of looping.
It might be a canditate for hashing, as it is stated in the code:
"// REVISIT: we might want to cache our own info..."
Here is a diff agains the 10.1.3.1 source for
org.apache.derby.iapi.util.StringUtil
22a23
> import java.util.Hashtable;
319c320,326
< return
s1.toUpperCase(Locale.ENGLISH).equals(s2.toUpperCase(Locale.ENGLISH));
---
> {
> String s1Up = (String) uppercaseMap.get(s1);
> if (s1Up == null)
> {
> s1Up = s1.toUpperCase(Locale.ENGLISH);
> uppercaseMap.put(s1,s1Up);
> }
320a328,332
> String s2Up = (String) uppercaseMap.get(s2);
> if (s2Up == null)
> {
> s2Up = s2.toUpperCase(Locale.ENGLISH);
> uppercaseMap.put(s2,s2Up);
321a334
> return s1Up.equals(s2Up);
322a336,339
> //return
> s1.toUpperCase(Locale.ENGLISH).equals(s2.toUpperCase(Locale.ENGLISH));
> }
> }
> private static Hashtable uppercaseMap = new Hashtable();
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