包函数（Bag Functions）:
1. COUNT:
- 描述： 计算包中的元组数量。
- 示例：
A = LOAD 'data.txt' AS (name:chararray, age:int);
B = GROUP A BY age;
C = FOREACH B GENERATE group AS age, COUNT(A) AS count;
2. SUM:
- 描述： 对包中的元组进行求和。
- 示例：
A = LOAD 'data.txt' AS (name:chararray, amount:double);
B = GROUP A BY name;
C = FOREACH B GENERATE group AS name, SUM(A.amount) AS total_amount;
3. AVG:
- 描述： 计算包中元组的平均值。
- 示例：
A = LOAD 'data.txt' AS (name:chararray, age:int);
B = GROUP A BY name;
C = FOREACH B GENERATE group AS name, AVG(A.age) AS avg_age;
4. MIN 和 MAX:
- 描述： 计算包中元组的最小值和最大值。
- 示例：
A = LOAD 'data.txt' AS (name:chararray, score:int);
B = GROUP A BY name;
C = FOREACH B GENERATE group AS name, MIN(A.score) AS min_score, MAX(A.score) AS max_score;
元组函数（Tuple Functions）:
1. FLATTEN:
- 描述： 将包中的元组展平，使其成为顶层元组。
- 示例：
A = LOAD 'data.txt' AS (name:chararray, addresses:bag{tuple(city:chararray, zip:int)});
B = FOREACH A GENERATE name, FLATTEN(addresses) AS (city:chararray, zip:int);
2. TUPLE:
- 描述： 创建一个元组。
- 示例：
A = LOAD 'data.txt' AS (name:chararray, age:int);
B = FOREACH A GENERATE TOTUPLE(name, age) AS person;
3. TOBAG:
- 描述： 将元组转换为包。
- 示例：
A = LOAD 'data.txt' AS (name:chararray, age:int);
B = GROUP A BY name;
C = FOREACH B GENERATE group AS name, TOBAG(A.age) AS ages;
4. SIZE:
- 描述： 获取包或元组的大小。
- 示例：
A = LOAD 'data.txt' AS (name:chararray, addresses:bag{tuple(city:chararray, zip:int)});
B = FOREACH A GENERATE name, SIZE(addresses) AS num_addresses;
这些是一些在Apache Pig中用于处理包和元组的常见函数。这些函数允许你对数据进行聚合、转换和组织，以满足特定的分析需求。
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