[ http://issues.apache.org/jira/browse/DERBY-1862?page=all ]
Andreas Korneliussen updated DERBY-1862:
----------------------------------------
Attachment: DERBY-1862.diff
Attached is a patch which uses another approach to improve the
SQLEqualsIgnoreCase method. The patch check the identity and length of the
strings to be compared, before doing conversions to uppercase with english
locale.
String.toUpperCase(..) with english locale, should return a string with the
same number of characters, and it should therefore be valid to do a check of
number of characters before doing any conversions.
The patch which is posted as part of the description, will leak memory, since
strings are never removed from the upperCaseMap.
> 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
> Attachments: DERBY-1862.diff
>
>
> 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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