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https://issues.apache.org/jira/browse/DRILL-4573?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15233836#comment-15233836
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ASF GitHub Bot commented on DRILL-4573:
---------------------------------------
Github user hsuanyi commented on a diff in the pull request:
https://github.com/apache/drill/pull/458#discussion_r59125807
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/CharSequenceWrapper.java
---
@@ -0,0 +1,49 @@
+/**
+ * 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 io.netty.buffer.DrillBuf;
+
+public class CharSequenceWrapper implements CharSequence {
+
+ private int start;
+ private int end;
+ private DrillBuf buffer;
+
+ @Override
+ public int length() {
+ return end - start;
+ }
+
+ @Override
+ public char charAt(int index) {
+ return (char) buffer.getByte(start + index);
--- End diff --
We might need to check if the index falls into the legal bounds.
> Zero copy LIKE, REGEXP_MATCHES, SUBSTR
> --------------------------------------
>
> Key: DRILL-4573
> URL: https://issues.apache.org/jira/browse/DRILL-4573
> Project: Apache Drill
> Issue Type: Improvement
> Reporter: jean-claude
> Priority: Minor
> Attachments: DRILL-4573.1.patch.txt
>
>
> All the functions using the java.util.regex.Matcher are currently creating
> Java string objects to pass into the matcher.reset().
> However this creates unnecessary copy of the bytes and a Java string object.
> The matcher uses a CharSequence, so instead of making a copy we can create an
> adapter from the DrillBuffer to the CharSequence interface.
> Gains of 25% in execution speed are possible when going over VARCHAR of 36
> chars. The gain will be proportional to the size of the VARCHAR.
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