[GitHub] drill pull request #1015: DRILL-5899: Simple pattern matchers can work with ...

[paul-rogers <gi...@git.apache.org>]

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`


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