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Date: Tue, 2 Oct 2012 04:19:09 +1100 (NCT)
From: "Dmitriy V. Ryaboy (JIRA)" <jira@apache.org>
To: pig-dev@hadoop.apache.org
Message-ID: <1287672735.148690.1349111949865.JavaMail.jiratomcat@arcas>
In-Reply-To: <1467696811.120593.1348551669073.JavaMail.jiratomcat@arcas>
Subject: [jira] [Commented] (PIG-2931) $ signs in the replacement string
 make parameter substitution fail
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    [ https://issues.apache.org/jira/browse/PIG-2931?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13466961#comment-13466961 ] 

Dmitriy V. Ryaboy commented on PIG-2931:
----------------------------------------

The patch looks correct, but I can't help but wonder if anyone might be (ab)using the current behavior.. second opinion?
                
> $ signs in the replacement string make parameter substitution fail
> ------------------------------------------------------------------
>
>                 Key: PIG-2931
>                 URL: https://issues.apache.org/jira/browse/PIG-2931
>             Project: Pig
>          Issue Type: Bug
>    Affects Versions: 0.10.0
>            Reporter: Cheolsoo Park
>            Assignee: Cheolsoo Park
>             Fix For: 0.11
>
>         Attachments: PIG-2931.patch
>
>
> To reproduce the issue, use the following pig script:
> {code:title=test.pig}
> a = load 'data';
> b = filter by $FILTER;
> {code}
> and run the following command:
> {code}
> pig -x local -dryrun -f test.pig -p FILTER="(\$0 == 'a')"
> {code}
> This generates the following script:
> {code:title=test.pig.substituted}
> a = load 'data';
> b = filter by ($FILTER == 'a');
> {code}
> However this should be:
> {code}
> a = load 'data';
> b = filter by ($0 == 'a');
> {code}
> This is because Pig calls replaceFirst() with a replacement string that include a $ sign as follows:
> {code}
> "$FILTER".replaceFirst("\\$FILTER", "($0 == 'a')"));
> {code}
> To treat $ signs as literals in the replacement string, we must escape them. Please see the [Java doc|http://docs.oracle.com/javase/6/docs/api/java/util/regex/Matcher.html#replaceFirst(java.lang.String)] for Matcher class for explanation:
> {quote}
> Note that backslashes (\) and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string. Dollar signs may be treated as references to captured subsequences as described above, and backslashes are used to escape literal characters in the replacement string.
> {quote}

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