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
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