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From "Daniel John Debrunner (JIRA)" <derby-...@db.apache.org>
Subject [jira] Created: (DERBY-731) org.apache.derby.impl.sql.compile.StringSlice is an inefficient way to do substring
Date Tue, 29 Nov 2005 15:14:30 GMT
org.apache.derby.impl.sql.compile.StringSlice is an inefficient way to do substring
-----------------------------------------------------------------------------------

         Key: DERBY-731
         URL: http://issues.apache.org/jira/browse/DERBY-731
     Project: Derby
        Type: Improvement
  Components: SQL  
    Reporter: Daniel John Debrunner
 Assigned to: Daniel John Debrunner 
    Priority: Trivial
     Fix For: 10.2.0.0


StringSlicer is a class that is basically implementing String.substring() with an optional
trim in an inefficient manner.
It creates a char array from the original string and uses this new array to create sub strings.
This means one allocation
and copy for the original char array and another allocation and copy for every subsequent
slice operation.

String.substring performs the same functionality but it can create sub-strings without the
character array allocation
and copy by re-using the character arrray hidden within the original string.

I've been running tests with a additional code in StringSlicer that compares its output with
that of String.substring with
no differences. One minor annoyance is that StringSlicer uses an inclusive end offset while
String.substring uses an
exclusive end offset.

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