MaxCompute:Example: Obtain the values of strings that have delimiters

Description

In this example, a UDF named UDF_EXTRACT_KEY_VALUE_WITH_SPLIT is registered. The following section describes the function syntax and input parameters.

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

• Function description: This function uses the delimiter specified by split1 to obtain key-value pairs from the string specified by s and uses the delimiter specified by split2 to obtain the keys and values. Then, the value that corresponds to the key specified by keyname is returned. Unlike the UDF that is used to obtain the values of strings that have no delimiters, this UDF applies to strings that have delimiters in keys or values.

• Parameters:

  • s: the string that you want to split, which is of the STRING type. This parameter is required.

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

  • split2: the key/value delimiter that you use to obtain the keys and values, which is of the STRING type. This parameter is required.

  • keyname: the key whose value you want to obtain, which is of the STRING type. This parameter is required.

Development and usage procedure

1. Write a UDF

package com.aliyun.rewrite; // The package name, which is user-defined. 
import com.aliyun.odps.udf.UDF;

public class ExtractKeyValueWithSplit extends UDF{
    /**
     * Use split1 to split the string and obtain key-value pairs. Then, use split2 to split the key-value pairs and obtain the keys and values.
     * @param str    The source string.
     * @param split1  The delimiter that is used to split a string and obtain key-value pairs.
     * @param split2  The delimiter that is used to split key-value pairs and obtain the keys and values.
     * @param keyname The name of the key whose value you want to obtain.
     * @return The returned value.
     */
    public String evaluate(String str, String split1, String split2, String keyname) {
        if(str==null || split1==null || split2==null || keyname==null){
            return null;
        }
        try {
            // Combine keyname and split2.
            String keySplit = keyname + split2;

            // Traverse the string. Use split1 to split the string and obtain key-value pairs. 
            for(String subStr: str.split(split1)){
                // Use split2 to split the key-value pairs and obtain the keys and values. Then, obtain the value that corresponds to a specific key.
                if (subStr.startsWith(keySplit)){
                    return subStr.substring(keySplit.length());
                }
            }
        } catch (Exception e) {
            return null;
        }
        return null;
    }
}

from odps.udf import annotate


@annotate("string,string,string,string->string")
class ExtractKeyValueWithSplit(object):
    def evaluate(self, s, split1, split2, keyname):
        if not s:
            return None
        key_split = keyname + split2
        # Traverse the string. Use split1 to split the string and obtain key-value pairs. 
        for subStr in s.split(split1):
            # Use split2 to split the key-value pairs and obtain the keys and values. Then, obtain the value that corresponds to a specific key.
            if subStr.startswith(key_split):
                return subStr[len(key_split):]

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


@annotate("string,string,string,string->string")
class ExtractKeyValueWithSplit(object):
    def evaluate(self, s, split1, split2, keyname):
        if not s:
            return None
        key_split = keyname + split2
        # Traverse the string. Use split1 to split the string and obtain key-value pairs. 
        for subStr in s.split(split1):
            # Use split2 to split the key-value pairs and obtain the keys and values. Then, obtain the value that corresponds to a specific key.
            if subStr.startswith(key_split):
                return subStr[len(key_split):]

2. Upload resources and register the UDF

After you write and debug a UDF, you must upload the UDF code to MaxCompute and register the UDF. In this example, the UDF named UDF_EXTRACT_KEY_VALUE_WITH_SPLIT is registered. For more information about how to upload and register a Java UDF, see Package a Java program, upload the package, and create a MaxCompute UDF. For more information about how to upload and register a Python UDF, see Upload a Python program and create a MaxCompute UDF.

3. Use the UDF

After you register the UDF, run the following commands to obtain the value that corresponds to the key name from a key-value pair string. The value that corresponds to the key name contains delimiters.

set odps.sql.python.version=cp37; -- If you want to use a Python 3 UDF, run this command.
SELECT UDF_EXTRACT_KEY_VALUE_WITH_SPLIT('name:zhangsang:man;age:2;', ';', ':', 'name');

The following result is returned:

+--------------+
| _c0          |
+--------------+
| zhangsan:man |
+--------------+