无法推断COUNT函数

Question

我正在尝试编写一个pig latin脚本来提取我已经过滤的数据集的计数.

到目前为止这是脚本:

/* scans by title */

scans           = LOAD '/hive/scans/*' USING PigStorage(',') AS (thetime:long,product_id:long,lat:double,lon:double,user:chararray,category:chararray,title:chararray);
productscans    = FILTER scans BY (title MATCHES 'proactiv');
scancount       = FOREACH productscans GENERATE COUNT($0);
DUMP scancount;

出于某种原因,我收到错误:

无法将org.apache.pig.builtin.COUNT的匹配函数推断为多个或不适合.请使用明确的演员.

我在这做错了什么？我假设它与我传入的字段类型有关,但我似乎无法解决这个问题.

TIA,Jason

Answer 1

这就是你要找的东西(所有人都将所有东西放在一个袋子里,然后计算物品):

scans           = LOAD '/hive/scans/*' USING PigStorage(',') AS (thetime:long,product_id:long,lat:double,lon:double,user:chararray,category:chararray,title:chararray);
productscans    = FILTER scans BY (title MATCHES 'proactiv');
grouped         = GROUP productscans ALL;
count           = FOREACH grouped GENERATE COUNT(productscans);
dump count;

Answer 2

COUNT 需要前面的GROUP ALL语句用于全局计数，而GROUP BY语句用于组计数。

您可以使用以下任何一种：

scans           = LOAD '/hive/scans/*' USING PigStorage(',') AS (thetime:long,product_id:long,lat:double,lon:double,user:chararray,category:chararray,title:chararray);
productscans    = FILTER scans BY (title MATCHES 'proactiv');
grouped         = GROUP productscans ALL;
count           = FOREACH grouped GENERATE COUNT(productscans);
DUMP scancount;

要么

scans           = LOAD '/hive/scans/*' USING PigStorage(',') AS (thetime:long,product_id:long,lat:double,lon:double,user:chararray,category:chararray,title:chararray);
productscans    = FILTER scans BY (title MATCHES 'proactiv');
grouped         = GROUP productscans ALL;
count           = FOREACH grouped GENERATE COUNT($1);
DUMP scancount;