在猪中逃脱美元符号? [英] Escaping a Dollar Sign in Pig?

问题描述

这在 0.9.2 中不是问题，但在 0.10 中，当我尝试访问带有美元符号的映射中的键时，我被我未定义变量的错误所困扰.具体:

This wasn't a problem in 0.9.2, but in 0.10, when I try to access a key in a map that has a dollar sign in it, I get hammered with errors that I haven't defined the variable. Specifically:

blah = FOREACH meh GENERATE source, json_post_id#'$id' AS post_id;

返回

Undefined parameter : id

这很好，也有道理，但是当我修改为:

That's fine and makes sense, but when I amend it to:

blah = FOREACH meh GENERATE source, json_post_id#'\$id' AS post_id;

我明白了:

Unexpected character '$'

想法?

忘了提及:也尝试过使用 2 个反斜杠和 3 个反斜杠.没有骰子.[/编辑]

Forgot to mention: have tried with 2 backslashes and 3 backslashes as well. No dice. [/Edit]

推荐答案

1. 基于对您的邮件存档的回复发布，看起来行为在使用 Grunt shell 并将其作为脚本运行时会有所不同."

1. Based on a response to your Mail Archive Posting, it looks like the behavior will be "different when using Grunt shell and running it as a script."

输入文件

cheolsoo@localhost:~/workspace/pig-svn $cat 1.txt $id,a

咕噜声

没有反斜杠的 $ 有效:

The $ with no backslash works:

grunt> A = LOAD '1.txt' USING PigStorage(',') AS (k:chararray,
v:chararray); grunt> B = FOREACH A GENERATE TOMAP(k, v) AS M; grunt> C
= FOREACH B GENERATE M#'$id'; grunt> DUMP C; (a)

脚本

带有单个反斜杠的 $ 有效:

The $ with a single backslash works:

cheolsoo@localhost:~/workspace/pig-svn $cat test.pig A = LOAD '1.txt' 
USING PigStorage(',') AS (k:chararray, v:chararray); B = FOREACH A
GENERATE TOMAP(k, v) AS M; C = FOREACH B GENERATE M#'\$id'; DUMP C;

cheolsoo@localhost:~/workspace/pig-svn $./bin/pig -x local test.pig
(a)

此外，来自分割字符串的猪问题(STRSPLIT)，您是否尝试过以下任一方法.

Also, from Pig problem with split string(STRSPLIT), have you tried either of the following.

• 正确转义字符 u0024.使用单引号或双引号测试 single 以查看是否有所不同.这个答案表明单引号有所不同，但值得一提.

• Correctly escaping the character u0024. Test single using single or double quotes to see if that makes a difference. This answer shows that the single quote makes a difference which you have but it's worth mentioning.

或者，尽管相关，将循环分解为一个块.

blah = FOREACH meh {
    GENERATE source, json_post_id#'$id' AS post_id; 
}

看起来您正在连接一个 id.确保您不会使用 CONCAT().http://pig.apache.org/docs/r0.10.0/func.html#concat

It looks like you are concatenating an id. Make sure you are not suppose to be using CONCAT(). http://pig.apache.org/docs/r0.10.0/func.html#concat

根据Class PigStorage 文档(Pig 0.10.0 API):

According to the Class PigStorage documentation (Pig 0.10.0 API):

使用字符分隔符将输入行解析为字段的加载函数.默认分隔符是制表符.您可以将任何字符指定为文字(a")、已知转义字符(\t")或十进制或十六进制值(\u001"、\x0A").

A load function that parses a line of input into fields using a character delimiter. The default delimiter is a tab. You can specify any character as a literal ("a"), a known escape character ("\t"), or a dec or hex value ("\u001", "\x0A").

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