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From: paul-rogers <git@git.apache.org>
To: dev@drill.apache.org
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References: <git-pr-1001-drill@git.apache.org>
In-Reply-To: <git-pr-1001-drill@git.apache.org>
Subject: [GitHub] drill pull request #1001: JIRA DRILL-5879: Like operator performance improve...
Content-Type: text/plain
Message-Id: <20171019004532.68B02DFAB2@git1-us-west.apache.org>
Date: Thu, 19 Oct 2017 00:45:32 +0000 (UTC)
archived-at: Thu, 19 Oct 2017 00:45:40 -0000

Github user paul-rogers commented on a diff in the pull request:

    https://github.com/apache/drill/pull/1001#discussion_r145576718
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/SqlPatternContainsMatcher.java ---
    @@ -17,36 +17,133 @@
      */
     package org.apache.drill.exec.expr.fn.impl;
     
    -public class SqlPatternContainsMatcher implements SqlPatternMatcher {
    +public final class SqlPatternContainsMatcher implements SqlPatternMatcher {
       final String patternString;
       CharSequence charSequenceWrapper;
       final int patternLength;
     
       public SqlPatternContainsMatcher(String patternString, CharSequence charSequenceWrapper) {
    -    this.patternString = patternString;
    +    this.patternString       = patternString;
         this.charSequenceWrapper = charSequenceWrapper;
    -    patternLength = patternString.length();
    +    patternLength            = patternString.length();
       }
     
       @Override
    -  public int match() {
    -    final int txtLength = charSequenceWrapper.length();
    -    int patternIndex = 0;
    -    int txtIndex = 0;
    +  public final int match() {
    +    // The idea is to write loops with simple condition checks to allow the Java Hotspot vectorize
    +    // the generate code.
    +    if (patternLength == 1) {
    +      return match_1();
    +    } else if (patternLength == 2) {
    +      return match_2();
    +    } else if (patternLength == 3) {
    +      return match_3();
    +    } else {
    +      return match_N();
    +    }
    +  }
    +
    +  private final int match_1() {
    --- End diff --
    
    See note about UTF-8. If we don't care about the match position (that is, we don't need `strpos()`, and all we care is whether it matches or not, then we can do the work on the undecoded UTF-8 bytes, saving a large amount of complexity.


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