[MAPREDUCE-2380] Multiple replace function call can be replaced with a single for loop to improve performance

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 0.21.0
• Component/s: tools/rumen
• Assignee: Unassigned
• Reporter: Xiaoming Shi
• Created: 13/Mar/11 03:15
• Updated: 13/May/16 23:11

Description

./hadoop-0.21.0/mapred/src/tools/org/apache/hadoop/tools/rumen/LoggedTaskAttempt.java  line:362
./chukwa-0.4.0/src/java/org/apache/hadoop/chukwa/datacollection/writer/localfs/LocalWriter.java   line:249

4 consecutive replace() is called to remove the special characters. It's 3+ times slower than using a for loop
replace them all.

e.g.
 - str.replace('a', '#');
 - str.replace('b', '%');

 + StringBuilder sb = new StringBuilder( str.length() );
 + for (int i=0; i < str.length(); i++)
 +  {
 +           char c = str.charAt(i);
 +         if ( c == 'a' )
 +               sb.append('#');
 +       else if ( c== 'b' )
 +               sb.append('%');
 +       else 
 +              sb.append(c); 
 +  }
 +  str  = sb.toString();

This bug has the same problem as the MySQL bug : http://bugs.mysql.com/bug.php?id=45699

Issue Links

• is duplicated by: MAPREDUCE-2343 repeated replace() function calls damage the performance