com.splicemachine.derby.utils.SpliceStringFunctions.java Source code

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Here is the source code for com.splicemachine.derby.utils.SpliceStringFunctions.java

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/*
 * Copyright 2012 - 2016 Splice Machine, Inc.
 *
 * Licensed 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 com.splicemachine.derby.utils;

import java.util.concurrent.ExecutionException;
import java.util.regex.Pattern;

import org.apache.commons.lang3.text.WordUtils;

import org.spark_project.guava.cache.CacheBuilder;
import org.spark_project.guava.cache.CacheLoader;
import org.spark_project.guava.cache.LoadingCache;

/**
 * Implementation of standard Splice String functions,
 * in particular those represented as system procedures
 * in the SYSFUN schema, such that they can be invoked
 * using the same SQL syntax as the true built-in functions
 * (e.g., SUBSTR, LOCATE, etc.), without specifying
 * the schema prefix.
 * 
 * @author Walt Koetke
 */

public class SpliceStringFunctions {

    /**
     * Implements logic for the SQL function INSTR.
     * 
     * @param srcStr the source string to be checked for its contents
     * @param subStr the substring to be found in the source string
     * 
     * @return position (as non zero integer) within the source string
     * where the substring was found, or 0 (zero) if not found.
     */
    public static int INSTR(String srcStr, String subStr) {
        // Matches support in MySql these two arguments,
        // although Oracle's has some additional arguments
        // (starting position and occurrence count).
        // We could add these if we add support for
        // optional arguments.

        if (srcStr == null)
            return 0;
        if (subStr == null || subStr.isEmpty())
            return 0;
        // Returns position starting from zero or -1 if not found
        int index = srcStr.indexOf(subStr);
        // Return position starting from 1 or 0 if not found
        return index + 1;
    }

    /**
     * Implements logic for the SQL function INITCAP.
     * 
     * @param source the String to be capitalized
     * 
     * @return the capitalized String
     */
    public static String INITCAP(String source) {
        return WordUtils.capitalizeFully(source);
    }

    /**
     * Implements logic for the SQL function CONCAT.
     * 
     * @param arg1 first string
     * @param arg2 second string
     * 
     * @return concatenation of arg1 and arg2
     */
    public static String CONCAT(String arg1, String arg2) {
        // Per MySql documentation, if any argument is NULL,
        // function returns NULL.
        if (arg1 == null || arg2 == null) {
            return null;
        }
        return arg1.concat(arg2);
    }

    /**
     * Implements logic for the SQL function REGEXPLIKE.
     * 
     * @param s string to be evaluated
     * @param regexp regular expression
     * 
     * @return flag indicating whether or not there is a match
     */
    public static boolean REGEXP_LIKE(String s, String regexp) {
        try {
            return patternCache.get(regexp).matcher(s).matches();
        } catch (ExecutionException e) {
            throw new RuntimeException(String.format("Unable to fetch Pattern for regexp [%s]", regexp), e);
        }
    }

    private static LoadingCache<String, Pattern> patternCache = CacheBuilder.newBuilder().maximumSize(100)
            .build(new CacheLoader<String, Pattern>() {
                @Override
                public Pattern load(String regexp) {
                    return Pattern.compile(regexp, Pattern.CASE_INSENSITIVE);
                }
            });
}