我有一个逗号分隔的.txt文件，我想 DUMP 这个 AVG 所有人的年龄 Males .

records = LOAD 'file:/home/gautamshaw/Documents/PigDemo_CommaSep.txt' USING PigStorage(',') AS (firstname:chararray,lastname:chararray,age:int,sex:chararray);
filter_by_male = FILTER records BY sex == 'M';
grouped = GROUP filter_by_male ALL;
average_male_age = FOREACH grouped GENERATE AVG(records.age);

我的电脑出错了 FOREACH 生产线：

ERROR org.apache.pig.tools.grunt.Grunt - ERROR 1045: 
<line 6, column 44> Could not infer the matching function for org.apache.pig.builtin.AVG as multiple or none of them fit. Please use an explicit cast.

请给我建议。