MaxCompute:Example: Obtain values of strings that do not have delimiters

Description

In this example, a UDF named UDF_EXTRACT_KEY_VALUE is created.

• Syntax:

  string UDF_EXTRACT_KEY_VALUE(string <s>, string <split1>, string <split2>, string <keyname>) 

• Description:

  Uses split1 to split the string s into key-value pairs, uses split2 to split the key-value pairs into keys and values, and then obtains the value of the key that is specified by keyname.

  Note

  This UDF is not suitable for a string that has delimiters. For more information about how to obtain the value of a specific key in a string that has delimiters, see Example: Obtain the values of strings that have delimiters.

• Parameters:

  • s: the source string. The value of this parameter is of the STRING data type. This parameter is required.

  • split1: the string delimiter that you use to obtain key-value pairs. The value of this parameter is of the STRING data type. This parameter is required.

  • split2: the key-value delimiter that you use to obtain keys and values. The value of this parameter is of the STRING data type. This parameter is required.

  • keyname: the key whose value you want to obtain. The value of this parameter is of the STRING data type. This parameter is required.

Procedure

1. Write a UDF

package com.aliyun.rewrite; // Specify a package name. 
import com.aliyun.odps.udf.UDF;

import java.util.HashMap;
import java.util.Map;

public class ExtractKeyValue extends UDF{
    private static final int KEY_VALUE_LENGTH = 2;

    /**
     * Use split1 to split the string into key-value pairs. Then, use split2 to split the key-value pairs into keys and values.
     * @param str    The source string.
     * @param split1  The delimiter that is used to split a string into key-value pairs.
     * @param split2  The delimiter that is used to split key-value pairs into keys and values.
     * @param keyname The name of the key whose value you want to obtain.
     * @return The return value.
     */
    public String evaluate(String str, String split1, String split2, String keyname) {
        try {
            // Use split1 to split a string into key-value pairs.
            if (str == null || "".equals(str)) {
                return null;
            }
            Map<String, String> keyValueCache = new HashMap<>(8);
            String[] extractedKeyValues = str.split(split1);

            // Use split2 to split the obtained key-value pairs into keys and values.
            for (String keyValue : extractedKeyValues) {
                storeKeyValue(keyValueCache, keyValue, split2);
            }

            // Obtain the value of the specified key.
            return keyValueCache.get(keyname);
        } catch (Exception e) {
            return null;
        }
    }

    /**
     * Use the split parameter to split key-value pairs. Then, cache the obtained results in keyValueCache.
     *
     * @param keyValueCache The cached key-value pairs that are obtained after splitting.
     * @param keyValue      The key-value pairs that you want to split.
     * @param split         The delimiter.
     */
    private void storeKeyValue(Map<String, String> keyValueCache, String keyValue, String split) {
        if (keyValue == null || "".equals(keyValue)) {
            return;
        }
        String[] keyValueArr = keyValue.split(split);
        if (keyValueArr.length == KEY_VALUE_LENGTH) {
            keyValueCache.put(keyValueArr[0], keyValueArr[1]);
        }
    }
}

from odps.udf import annotate


@annotate("string,string,string,string->string")
class ExtractKeyValue(object):
    def evaluate(self, s, split1, split2, keyname):
        if not s:
            return None
        # Use split1 to split a string into key-value pairs, and use split2 to split the key-value pairs into keys and values.
        key_value_cache = dict(kv.split(split2) for kv in s.split(split1) if kv)
        # Obtain the value of the specified key.
        return key_value_cache.get(keyname)

#coding:utf-8
from odps.udf import annotate


@annotate("string,string,string,string->string")
class ExtractKeyValue(object):
    def evaluate(self, s, split1, split2, keyname):
        if not s:
            return None
        # Use split1 to split a string into key-value pairs, and use split2 to split the key-value pairs into keys and values.
        key_value_cache = dict(kv.split(split2) for kv in s.split(split1) if kv)
        # Obtain the value of the specified key.
        return key_value_cache.get(keyname)

2. Upload resources and create a UDF

After you develop and debug UDF code, upload resources to MaxCompute and create a UDF. In this example, a UDF named UDF_EXTRACT_KEY_VALUE is created. For more information about how to upload resources and create a Java UDF, see Package a Java program, upload the package, and create a MaxCompute UDF. For more information about how to upload resources and create a Python UDF, see Upload a Python program and create a MaxCompute UDF.

3. Use the UDF

After the UDF is created, run the following commands to obtain the value of the name key from a key-value pair string:

set odps.sql.python.version=cp37; -- To use a UDF in Python 3, run this command.
SELECT UDF_EXTRACT_KEY_VALUE('name:zhangsan;age:21;',';',':','name');

The following result is returned:

+----------+
| _c0      |
+----------+
| zhangsan |
+----------+