Github user sachouche commented on a diff in the pull request:
https://github.com/apache/drill/pull/1001#discussion_r146952578
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/SqlPatternContainsMatcher.java
---
@@ -17,37 +17,166 @@
*/
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;
+ final MatcherFcn matcherFcn;
public SqlPatternContainsMatcher(String patternString, CharSequence
charSequenceWrapper) {
- this.patternString = patternString;
+ this.patternString = patternString;
this.charSequenceWrapper = charSequenceWrapper;
- patternLength = patternString.length();
+ patternLength = patternString.length();
+
+ // The idea is to write loops with simple condition checks to allow
the Java Hotspot achieve
+ // better optimizations (especially vectorization)
+ if (patternLength == 1) {
+ matcherFcn = new Matcher1();
--- End diff --
I ran two types of tests to evaluate the generic vs custom method:
Test1 - A match does exist
o Custom method is 3x faster because the code will go to the "else" part
o A nested loop is always slower than unrolled code (the loop is also
correlated with the outer one); please refer to this article
(https://en.wikipedia.org/wiki/Loop_unrolling) on the benefits of loop unrolling
o Older match function performed in 59sec
Test2- A match doesn't exist
o Custom method and generic one perform in 15sec; this is because both
perform a comparison and proceed to the next iteration
o Older match function performed in 45sec
---
