[jira] [Commented] (DRILL-5899) Simple pattern matchers can work with DrillBuf directly

2017-11-13 Thread ASF GitHub Bot (JIRA)

[ 
https://issues.apache.org/jira/browse/DRILL-5899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16249465#comment-16249465
 ] 

ASF GitHub Bot commented on DRILL-5899:
---

Github user asfgit closed the pull request at:

https://github.com/apache/drill/pull/1015


> Simple pattern matchers can work with DrillBuf directly
> ---
>
> Key: DRILL-5899
> URL: https://issues.apache.org/jira/browse/DRILL-5899
> Project: Apache Drill
>  Issue Type: Improvement
>  Components: Execution - Flow
>Reporter: Padma Penumarthy
>Assignee: Padma Penumarthy
>Priority: Critical
>  Labels: ready-to-commit
>
> For the 4 simple patterns we have i.e. startsWith, endsWith, contains and 
> constant,, we do not need the overhead of charSequenceWrapper. We can work 
> with DrillBuf directly. This will save us from doing isAscii check and UTF8 
> decoding for each row.
> UTF-8 encoding ensures that no UTF-8 character is a prefix of any other valid 
> character. So, instead of decoding varChar from each row we are processing, 
> encode the patternString once during setup and do raw byte comparison. 
> Instead of bounds checking and reading one byte at a time, we get the whole 
> buffer in one shot and use that for comparison.
> This improved overall performance for filter operator by around 20%. 



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[jira] [Commented] (DRILL-5899) Simple pattern matchers can work with DrillBuf directly

2017-11-07 Thread ASF GitHub Bot (JIRA)

[ 
https://issues.apache.org/jira/browse/DRILL-5899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16243315#comment-16243315
 ] 

ASF GitHub Bot commented on DRILL-5899:
---

Github user ppadma commented on the issue:

https://github.com/apache/drill/pull/1015
  
@paul-rogers updated with latest review comments taken care of. Please take 
a look.


> Simple pattern matchers can work with DrillBuf directly
> ---
>
> Key: DRILL-5899
> URL: https://issues.apache.org/jira/browse/DRILL-5899
> Project: Apache Drill
>  Issue Type: Improvement
>  Components: Execution - Flow
>Reporter: Padma Penumarthy
>Assignee: Padma Penumarthy
>Priority: Critical
>
> For the 4 simple patterns we have i.e. startsWith, endsWith, contains and 
> constant,, we do not need the overhead of charSequenceWrapper. We can work 
> with DrillBuf directly. This will save us from doing isAscii check and UTF8 
> decoding for each row.
> UTF-8 encoding ensures that no UTF-8 character is a prefix of any other valid 
> character. So, instead of decoding varChar from each row we are processing, 
> encode the patternString once during setup and do raw byte comparison. 
> Instead of bounds checking and reading one byte at a time, we get the whole 
> buffer in one shot and use that for comparison.
> This improved overall performance for filter operator by around 20%. 



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[jira] [Commented] (DRILL-5899) Simple pattern matchers can work with DrillBuf directly

2017-11-07 Thread ASF GitHub Bot (JIRA)

[ 
https://issues.apache.org/jira/browse/DRILL-5899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16243238#comment-16243238
 ] 

ASF GitHub Bot commented on DRILL-5899:
---

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

https://github.com/apache/drill/pull/1015#discussion_r149554195
  
--- Diff: 
exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/SqlPatternContainsMatcher.java
 ---
@@ -17,37 +17,48 @@
  */
 package org.apache.drill.exec.expr.fn.impl;
 
-public class SqlPatternContainsMatcher implements SqlPatternMatcher {
-  final String patternString;
-  CharSequence charSequenceWrapper;
-  final int patternLength;
-
-  public SqlPatternContainsMatcher(String patternString, CharSequence 
charSequenceWrapper) {
-this.patternString = patternString;
-this.charSequenceWrapper = charSequenceWrapper;
-patternLength = patternString.length();
+import io.netty.buffer.DrillBuf;
+
+public class SqlPatternContainsMatcher extends AbstractSqlPatternMatcher {
+
+  public SqlPatternContainsMatcher(String patternString) {
+super(patternString);
   }
 
   @Override
-  public int match() {
-final int txtLength = charSequenceWrapper.length();
-int patternIndex = 0;
-int txtIndex = 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;
-  } else {
-patternIndex++;
+  public int match(int start, int end, DrillBuf drillBuf) {
+
+if (patternLength == 0) { // Everything should match for null pattern 
string
+  return 1;
+}
+
+final int txtLength = end - start;
+
+// no match if input string length is less than pattern length
+if (txtLength < patternLength) {
+  return 0;
+}
+
+outer:
+for (int txtIndex = 0; txtIndex < txtLength; txtIndex++) {
+
+  // boundary check
+  if (txtIndex + patternLength > txtLength) {
--- End diff --

Better:
```
int end = txtLength - patternLength;
for (int txtIndex = 0; txtIndex < end; txtIndex++) {
```
And omit the boundary check on every iteration. That is, no reason to 
iterate past the last possible match, then use an if-statement to shorten the 
loop. Just shorten the loop.


> Simple pattern matchers can work with DrillBuf directly
> ---
>
> Key: DRILL-5899
> URL: https://issues.apache.org/jira/browse/DRILL-5899
> Project: Apache Drill
>  Issue Type: Improvement
>  Components: Execution - Flow
>Reporter: Padma Penumarthy
>Assignee: Padma Penumarthy
>Priority: Critical
>
> For the 4 simple patterns we have i.e. startsWith, endsWith, contains and 
> constant,, we do not need the overhead of charSequenceWrapper. We can work 
> with DrillBuf directly. This will save us from doing isAscii check and UTF8 
> decoding for each row.
> UTF-8 encoding ensures that no UTF-8 character is a prefix of any other valid 
> character. So, instead of decoding varChar from each row we are processing, 
> encode the patternString once during setup and do raw byte comparison. 
> Instead of bounds checking and reading one byte at a time, we get the whole 
> buffer in one shot and use that for comparison.
> This improved overall performance for filter operator by around 20%. 



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[jira] [Commented] (DRILL-5899) Simple pattern matchers can work with DrillBuf directly

2017-11-07 Thread ASF GitHub Bot (JIRA)

[ 
https://issues.apache.org/jira/browse/DRILL-5899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16243237#comment-16243237
 ] 

ASF GitHub Bot commented on DRILL-5899:
---

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

https://github.com/apache/drill/pull/1015#discussion_r149552453
  
--- Diff: 
exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/AbstractSqlPatternMatcher.java
 ---
@@ -0,0 +1,61 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.drill.exec.expr.fn.impl;
+
+import com.google.common.base.Charsets;
+import org.apache.drill.common.exceptions.UserException;
+import java.nio.ByteBuffer;
+import java.nio.CharBuffer;
+import java.nio.charset.CharacterCodingException;
+import java.nio.charset.CharsetEncoder;
+import static 
org.apache.drill.exec.expr.fn.impl.StringFunctionHelpers.logger;
+
+// To get good performance for most commonly used pattern matches
--- End diff --

Javadoc?

```
/**
 * This is a Javadoc comment and appears in generated documentation.
 */
// This is a plain comment and does not appear in documentation.
```


> Simple pattern matchers can work with DrillBuf directly
> ---
>
> Key: DRILL-5899
> URL: https://issues.apache.org/jira/browse/DRILL-5899
> Project: Apache Drill
>  Issue Type: Improvement
>  Components: Execution - Flow
>Reporter: Padma Penumarthy
>Assignee: Padma Penumarthy
>Priority: Critical
>
> For the 4 simple patterns we have i.e. startsWith, endsWith, contains and 
> constant,, we do not need the overhead of charSequenceWrapper. We can work 
> with DrillBuf directly. This will save us from doing isAscii check and UTF8 
> decoding for each row.
> UTF-8 encoding ensures that no UTF-8 character is a prefix of any other valid 
> character. So, instead of decoding varChar from each row we are processing, 
> encode the patternString once during setup and do raw byte comparison. 
> Instead of bounds checking and reading one byte at a time, we get the whole 
> buffer in one shot and use that for comparison.
> This improved overall performance for filter operator by around 20%. 



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[jira] [Commented] (DRILL-5899) Simple pattern matchers can work with DrillBuf directly

2017-11-07 Thread ASF GitHub Bot (JIRA)

[ 
https://issues.apache.org/jira/browse/DRILL-5899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16243235#comment-16243235
 ] 

ASF GitHub Bot commented on DRILL-5899:
---

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

https://github.com/apache/drill/pull/1015#discussion_r149554356
  
--- Diff: 
exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/SqlPatternEndsWithMatcher.java
 ---
@@ -17,33 +17,30 @@
  */
 package org.apache.drill.exec.expr.fn.impl;
 
-public class SqlPatternEndsWithMatcher implements SqlPatternMatcher {
-  final String patternString;
-  CharSequence charSequenceWrapper;
-  final int patternLength;
-
-  public SqlPatternEndsWithMatcher(String patternString, CharSequence 
charSequenceWrapper) {
-this.charSequenceWrapper = charSequenceWrapper;
-this.patternString = patternString;
-this.patternLength = patternString.length();
+import io.netty.buffer.DrillBuf;
+
+public class SqlPatternEndsWithMatcher extends AbstractSqlPatternMatcher {
+
+  public SqlPatternEndsWithMatcher(String patternString) {
+super(patternString);
   }
 
   @Override
-  public int match() {
-int txtIndex = charSequenceWrapper.length();
-int patternIndex = patternLength;
-boolean matchFound = true; // if pattern is empty string, we always 
match.
+  public int match(int start, int end, DrillBuf drillBuf) {
+
+if ( (end - start) < patternLength) { // No match if input string 
length is less than pattern length.
--- End diff --

`( (end - start)` --> `(end - start`


> Simple pattern matchers can work with DrillBuf directly
> ---
>
> Key: DRILL-5899
> URL: https://issues.apache.org/jira/browse/DRILL-5899
> Project: Apache Drill
>  Issue Type: Improvement
>  Components: Execution - Flow
>Reporter: Padma Penumarthy
>Assignee: Padma Penumarthy
>Priority: Critical
>
> For the 4 simple patterns we have i.e. startsWith, endsWith, contains and 
> constant,, we do not need the overhead of charSequenceWrapper. We can work 
> with DrillBuf directly. This will save us from doing isAscii check and UTF8 
> decoding for each row.
> UTF-8 encoding ensures that no UTF-8 character is a prefix of any other valid 
> character. So, instead of decoding varChar from each row we are processing, 
> encode the patternString once during setup and do raw byte comparison. 
> Instead of bounds checking and reading one byte at a time, we get the whole 
> buffer in one shot and use that for comparison.
> This improved overall performance for filter operator by around 20%. 



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[jira] [Commented] (DRILL-5899) Simple pattern matchers can work with DrillBuf directly

2017-11-07 Thread ASF GitHub Bot (JIRA)

[ 
https://issues.apache.org/jira/browse/DRILL-5899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16243239#comment-16243239
 ] 

ASF GitHub Bot commented on DRILL-5899:
---

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

https://github.com/apache/drill/pull/1015#discussion_r149555002
  
--- Diff: 
exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/SqlPatternEndsWithMatcher.java
 ---
@@ -17,33 +17,30 @@
  */
 package org.apache.drill.exec.expr.fn.impl;
 
-public class SqlPatternEndsWithMatcher implements SqlPatternMatcher {
-  final String patternString;
-  CharSequence charSequenceWrapper;
-  final int patternLength;
-
-  public SqlPatternEndsWithMatcher(String patternString, CharSequence 
charSequenceWrapper) {
-this.charSequenceWrapper = charSequenceWrapper;
-this.patternString = patternString;
-this.patternLength = patternString.length();
+import io.netty.buffer.DrillBuf;
+
+public class SqlPatternEndsWithMatcher extends AbstractSqlPatternMatcher {
+
+  public SqlPatternEndsWithMatcher(String patternString) {
+super(patternString);
   }
 
   @Override
-  public int match() {
-int txtIndex = charSequenceWrapper.length();
-int patternIndex = patternLength;
-boolean matchFound = true; // if pattern is empty string, we always 
match.
+  public int match(int start, int end, DrillBuf drillBuf) {
+
+if ( (end - start) < patternLength) { // No match if input string 
length is less than pattern length.
+  return 0;
+}
 
 // simplePattern string has meta characters i.e % and _ and escape 
characters removed.
 // so, we can just directly compare.
-while (patternIndex > 0 && txtIndex > 0) {
-  if (charSequenceWrapper.charAt(--txtIndex) != 
patternString.charAt(--patternIndex)) {
-matchFound = false;
-break;
+for (int index = 1; index <= patternLength; index++) {
--- End diff --

```
int txtStart = end - patternLength;
if (txtStart < start) { return 0; }
for (int index = 0; index < patternLength; index++) {
   ... patternByteBuffer.get(index) ... drillBuf.getByte(txtStart + index) 
...
```



> Simple pattern matchers can work with DrillBuf directly
> ---
>
> Key: DRILL-5899
> URL: https://issues.apache.org/jira/browse/DRILL-5899
> Project: Apache Drill
>  Issue Type: Improvement
>  Components: Execution - Flow
>Reporter: Padma Penumarthy
>Assignee: Padma Penumarthy
>Priority: Critical
>
> For the 4 simple patterns we have i.e. startsWith, endsWith, contains and 
> constant,, we do not need the overhead of charSequenceWrapper. We can work 
> with DrillBuf directly. This will save us from doing isAscii check and UTF8 
> decoding for each row.
> UTF-8 encoding ensures that no UTF-8 character is a prefix of any other valid 
> character. So, instead of decoding varChar from each row we are processing, 
> encode the patternString once during setup and do raw byte comparison. 
> Instead of bounds checking and reading one byte at a time, we get the whole 
> buffer in one shot and use that for comparison.
> This improved overall performance for filter operator by around 20%. 



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[jira] [Commented] (DRILL-5899) Simple pattern matchers can work with DrillBuf directly

2017-11-07 Thread ASF GitHub Bot (JIRA)

[ 
https://issues.apache.org/jira/browse/DRILL-5899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16243236#comment-16243236
 ] 

ASF GitHub Bot commented on DRILL-5899:
---

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

https://github.com/apache/drill/pull/1015#discussion_r149552506
  
--- Diff: 
exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/AbstractSqlPatternMatcher.java
 ---
@@ -0,0 +1,61 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.drill.exec.expr.fn.impl;
+
+import com.google.common.base.Charsets;
+import org.apache.drill.common.exceptions.UserException;
+import java.nio.ByteBuffer;
+import java.nio.CharBuffer;
+import java.nio.charset.CharacterCodingException;
+import java.nio.charset.CharsetEncoder;
+import static 
org.apache.drill.exec.expr.fn.impl.StringFunctionHelpers.logger;
+
+// To get good performance for most commonly used pattern matches
+// i.e. CONSTANT('ABC'), STARTSWITH('%ABC'), ENDSWITH('ABC%') and 
CONTAINS('%ABC%'),
+// we have simple pattern matchers.
+// Idea is to have our own implementation for simple pattern matchers so 
we can
+// avoid heavy weight regex processing, skip UTF-8 decoding and char 
conversion.
+// Instead, we encode the pattern string and do byte comparison against 
native memory.
+// Overall, this approach
+// gives us orders of magnitude performance improvement for simple pattern 
matches.
+// Anything that is not simple is considered
+// complex pattern and we use Java regex for complex pattern matches.
+
+public abstract class AbstractSqlPatternMatcher implements 
SqlPatternMatcher {
+  final String patternString;
--- End diff --

`protected final`


> Simple pattern matchers can work with DrillBuf directly
> ---
>
> Key: DRILL-5899
> URL: https://issues.apache.org/jira/browse/DRILL-5899
> Project: Apache Drill
>  Issue Type: Improvement
>  Components: Execution - Flow
>Reporter: Padma Penumarthy
>Assignee: Padma Penumarthy
>Priority: Critical
>
> For the 4 simple patterns we have i.e. startsWith, endsWith, contains and 
> constant,, we do not need the overhead of charSequenceWrapper. We can work 
> with DrillBuf directly. This will save us from doing isAscii check and UTF8 
> decoding for each row.
> UTF-8 encoding ensures that no UTF-8 character is a prefix of any other valid 
> character. So, instead of decoding varChar from each row we are processing, 
> encode the patternString once during setup and do raw byte comparison. 
> Instead of bounds checking and reading one byte at a time, we get the whole 
> buffer in one shot and use that for comparison.
> This improved overall performance for filter operator by around 20%. 



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[jira] [Commented] (DRILL-5899) Simple pattern matchers can work with DrillBuf directly

2017-11-07 Thread ASF GitHub Bot (JIRA)

[ 
https://issues.apache.org/jira/browse/DRILL-5899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16243050#comment-16243050
 ] 

ASF GitHub Bot commented on DRILL-5899:
---

Github user ppadma commented on the issue:

https://github.com/apache/drill/pull/1015
  
@paul-rogers Thanks a lot for the review. Updated the PR with code review 
comments. Please take a look. 

Overall, good improvement with this change. Here are the numbers.

select count(*) from `/Users/ppenumarthy/MAPRTECH/padma/testdata` where 
l_comment like '%a' 
1.4 sec vs 7 sec

select count(*) from `/Users/ppenumarthy/MAPRTECH/padma/testdata` where 
l_comment like '%a%' 
6.5 sec vs 13.5 sec

select count(*) from `/Users/ppenumarthy/MAPRTECH/padma/testdata` where 
l_comment like 'a%' 
1.4 sec vs 5.8 sec

select count(*) from `/Users/ppenumarthy/MAPRTECH/padma/testdata` where 
l_comment like 'a' 
1.1.65 sec vs 5.8 sec


I think for "contains", improvement is not as much as others, probably 
because of nested for loops. @sachouche changes on top of these changes can 
improve further. 



> Simple pattern matchers can work with DrillBuf directly
> ---
>
> Key: DRILL-5899
> URL: https://issues.apache.org/jira/browse/DRILL-5899
> Project: Apache Drill
>  Issue Type: Improvement
>  Components: Execution - Flow
>Reporter: Padma Penumarthy
>Assignee: Padma Penumarthy
>Priority: Critical
>
> For the 4 simple patterns we have i.e. startsWith, endsWith, contains and 
> constant,, we do not need the overhead of charSequenceWrapper. We can work 
> with DrillBuf directly. This will save us from doing isAscii check and UTF8 
> decoding for each row.
> UTF-8 encoding ensures that no UTF-8 character is a prefix of any other valid 
> character. So, instead of decoding varChar from each row we are processing, 
> encode the patternString once during setup and do raw byte comparison. 
> Instead of bounds checking and reading one byte at a time, we get the whole 
> buffer in one shot and use that for comparison.
> This improved overall performance for filter operator by around 20%. 



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[jira] [Commented] (DRILL-5899) Simple pattern matchers can work with DrillBuf directly

2017-11-05 Thread ASF GitHub Bot (JIRA)

[ 
https://issues.apache.org/jira/browse/DRILL-5899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16239919#comment-16239919
 ] 

ASF GitHub Bot commented on DRILL-5899:
---

Github user paul-rogers commented on the issue:

https://github.com/apache/drill/pull/1015
  
Second long list of detailed comments sent privately to keep dev list 
traffic down.


> Simple pattern matchers can work with DrillBuf directly
> ---
>
> Key: DRILL-5899
> URL: https://issues.apache.org/jira/browse/DRILL-5899
> Project: Apache Drill
>  Issue Type: Improvement
>  Components: Execution - Flow
>Reporter: Padma Penumarthy
>Assignee: Padma Penumarthy
>Priority: Critical
>
> For the 4 simple patterns we have i.e. startsWith, endsWith, contains and 
> constant,, we do not need the overhead of charSequenceWrapper. We can work 
> with DrillBuf directly. This will save us from doing isAscii check and UTF8 
> decoding for each row.
> UTF-8 encoding ensures that no UTF-8 character is a prefix of any other valid 
> character. So, instead of decoding varChar from each row we are processing, 
> encode the patternString once during setup and do raw byte comparison. 
> Instead of bounds checking and reading one byte at a time, we get the whole 
> buffer in one shot and use that for comparison.
> This improved overall performance for filter operator by around 20%. 



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[jira] [Commented] (DRILL-5899) Simple pattern matchers can work with DrillBuf directly

2017-11-02 Thread ASF GitHub Bot (JIRA)

[ 
https://issues.apache.org/jira/browse/DRILL-5899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16237125#comment-16237125
 ] 

ASF GitHub Bot commented on DRILL-5899:
---

Github user ppadma commented on the issue:

https://github.com/apache/drill/pull/1015
  
@sachouche @paul-rogers Thanks for the review. I updated the PR with review 
comments. 

I made one more change.  Previously, I was copying native memory buffer 
into byte array and using it. Instead, if we go to native memory  directly, 
performance is significantly better. In fact,  it is 3 times faster :-)

Please review updated changes.



> Simple pattern matchers can work with DrillBuf directly
> ---
>
> Key: DRILL-5899
> URL: https://issues.apache.org/jira/browse/DRILL-5899
> Project: Apache Drill
>  Issue Type: Improvement
>  Components: Execution - Flow
>Reporter: Padma Penumarthy
>Assignee: Padma Penumarthy
>Priority: Critical
>
> For the 4 simple patterns we have i.e. startsWith, endsWith, contains and 
> constant,, we do not need the overhead of charSequenceWrapper. We can work 
> with DrillBuf directly. This will save us from doing isAscii check and UTF8 
> decoding for each row.
> UTF-8 encoding ensures that no UTF-8 character is a prefix of any other valid 
> character. So, instead of decoding varChar from each row we are processing, 
> encode the patternString once during setup and do raw byte comparison. 
> Instead of bounds checking and reading one byte at a time, we get the whole 
> buffer in one shot and use that for comparison.
> This improved overall performance for filter operator by around 20%. 



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