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  1. Derby
  2. DERBY-1862

Simple hash improves performance

    Details

    • Type: Improvement
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 10.1.2.1, 10.1.3.1
    • Fix Version/s: 10.2.1.6, 10.2.2.0, 10.3.1.4
    • Component/s: SQL
    • Labels:
      None
    • Environment:
      WinXp, JRE 1.5_6., Hibernate 3.1
    • Urgency:
      Normal
    • Bug behavior facts:
      Performance

      Description

      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();

        Attachments

        1. DERBY-1696v2.diff
          11 kB
          Andreas Korneliussen
        2. DERBY-1862.diff
          1 kB
          Andreas Korneliussen
        3. DERBY-1862v2.diff
          3 kB
          Andreas Korneliussen
        4. DERBY-1862v3.diff
          3 kB
          Andreas Korneliussen

          Activity

            People

            • Assignee:
              andreask Andreas Korneliussen
              Reporter:
              taoman Tore Andre Olmheim
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              Dates

              • Created:
                Updated:
                Resolved: