json—如何使用jsonloader为数组定义模式?

h43kikqp  于 2021-06-25  发布在  Pig
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我使用elephantbird项目将json文件加载到pig。但我不确定如何在加载时定义模式。没有找到相同的描述。
数据:

{"id":22522,"name":"Product1","colors":["Red","Blue"],"sizes":["S","M"]}
{"id":22523,"name":"Product2","colors":["White","Blue"],"sizes":["M"]}

代码:

feed = LOAD '$INPUT' USING com.twitter.elephantbird.pig.load.JsonLoader() AS products_json;

extracted_products = FOREACH feed GENERATE
    products_json#'id' AS id,
    products_json#'name' AS name,
    products_json#'colors' AS colors,
    products_json#'sizes' AS sizes;

describe extracted_products;

结果:

extracted_products: {id: chararray,name: bytearray,colors: bytearray,sizes: bytearray}

如何为它们提供正确的模式(int、string、array、array)以及如何将数组元素展平成行?
提前谢谢

ax6ht2ek

ax6ht2ek1#

要将json数组转换为元组:

feed = LOAD '$INPUT' USING com.twitter.elephantbird.pig.load.JsonLoader() AS products_json;

extracted_products = FOREACH feed GENERATE
products_json#'id' AS id:chararray,
products_json#'name' AS name:chararray,
products_json#'colors' AS colors:{t:(i:chararray)},
products_json#'sizes' AS sizes:{t:(i:chararray)};

压扁元组

flattened = foreach extracted_products generate id,flatten(colors);

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