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From "Tore Andre Olmheim (JIRA)" <derby-...@db.apache.org>
Subject [jira] Created: (DERBY-1862) Simple hash improves performance
Date Mon, 18 Sep 2006 08:28:22 GMT
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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