Github user paul-rogers commented on a diff in the pull request:
https://github.com/apache/drill/pull/1001#discussion_r145577894
--- 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() {
+ final CharSequence sequenceWrapper = charSequenceWrapper;
+ final int lengthToProcess = sequenceWrapper.length();
+ final char first_patt_char = patternString.charAt(0);
+
+ // simplePattern string has meta characters i.e % and _ and escape
characters removed.
+ // so, we can just directly compare.
+ for (int idx = 0; idx < lengthToProcess; idx++) {
+ char input_char = sequenceWrapper.charAt(idx);
+
+ if (first_patt_char != input_char) {
+ continue;
+ }
+ return 1;
+ }
+ return 0;
+ }
+
+ private final int match_2() {
+ final CharSequence sequenceWrapper = charSequenceWrapper;
+ final int lengthToProcess = sequenceWrapper.length() - 1;
+ final char first_patt_char = patternString.charAt(0);
+
+ // simplePattern string has meta characters i.e % and _ and escape
characters removed.
+ // so, we can just directly compare.
+ for (int idx = 0; idx < lengthToProcess; idx++) {
+ char input_char = sequenceWrapper.charAt(idx);
+
+ if (first_patt_char != input_char) {
+ continue;
+ } else {
+ char ch2_1 = sequenceWrapper.charAt(idx+1);
+ char ch2_2 = patternString.charAt(1);
+
+ if (ch2_1 == ch2_2) {
+ return 1;
+ }
+ }
+ }
+ return 0;
+ }
+
+ private final int match_3() {
+ final CharSequence sequenceWrapper = charSequenceWrapper;
+ final int lengthToProcess = sequenceWrapper.length() -2;
+ final char first_patt_char = patternString.charAt(0);
// simplePattern string has meta characters i.e % and _ and escape
characters removed.
// so, we can just directly compare.
- while (patternIndex < patternLength && txtIndex < txtLength) {
- if (patternString.charAt(patternIndex) !=
charSequenceWrapper.charAt(txtIndex)) {
- // Go back if there is no match
- txtIndex = txtIndex - patternIndex;
- patternIndex = 0;
+ for (int idx = 0; idx < lengthToProcess; idx++) {
+ char input_char = sequenceWrapper.charAt(idx);
+
+ if (first_patt_char != input_char) {
+ continue;
} else {
- patternIndex++;
+ char ch2_1 = sequenceWrapper.charAt(idx+1);
+ char ch2_2 = patternString.charAt(1);
+ char ch3_1 = sequenceWrapper.charAt(idx+2);
+ char ch3_2 = patternString.charAt(2);
+
+ if (ch2_1 == ch2_2 && ch3_1 == ch3_2) {
+ return 1;
+ }
}
- txtIndex++;
+ }
+ return 0;
+ }
+
+ private final int match_N() {
+
+ if (patternLength == 0) {
--- End diff --
Can't this be optimized away in the pattern parser stage? We should not be
calling this function if we had a zero-length pattern.
---
