尝试使用 Apache Pig 聚合数据时出错

Question

这是我的代码运行:

bigrams = LOAD 's3://******' AS (bigram:chararray, year:int, occurrences:int, books:int);
bg_tmp = filter bigrams BY (occurrences >= 300) AND (books >= 12);
bg_tmp_2 = GROUP bg_tmp ALL;
occ_cnt = FOREACH bg_tmp_2 GENERATE bigram, SUM(bg_tmp_2.occurrences);
x = LIMIT occ_cnt 100;
DUMP x;

这是我在计算时遇到的错误 occ_cnt

81201 [main] ERROR org.apache.pig.tools.grunt.Grunt  - ERROR 1200: Pig script failed to parse: <line 5, column 48> Invalid scalar projection: bg_tmp_218/10/26 16:05:07 ERROR grunt.Grunt: ERROR 1200: Pig script failed to parse: <line 5, column 48> Invalid scalar projection: bg_tmp_2
Details at logfile: /mnt/var/log/pig/pig_1540569826316.log

我不知道为什么会这样。我在 AWS EMR

上使用 Apache Pig 0.17.0 和 Hadoop 2.8.4

Answer 1

我会将您的查询重写为

bg_tmp_2 = GROUP bg_tmp by (bigram);
occ_cnt = FOREACH bg_tmp_2 GENERATE group, SUM(bg_tmp.occurrences);

正在替换 GROUP ALL，因为我认为您需要每个二元词项的 SUM。将 bg_tmp2 替换为 bg_tmp，因为您想在 bg_tmp_2 关系中引用 bg_tmp BAG。

（如果您运行 "describe bg_tmp_2"，您将看到以下架构）

bg_tmp_2: {group: chararray,bg_tmp: {(bigram: chararray,year: int,occurrences: int,books: int)}}

尝试使用 Apache Pig 聚合数据时出错

Error while trying aggregate data using Apache Pig

hadoop

apache-pig