[
https://issues.apache.org/jira/browse/PIG-3347?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13887203#comment-13887203
]
Julien Le Dem commented on PIG-3347:
------------------------------------
I thought that the field UIDs were used to track lineage across the plan.
[~aniket486] correct me if I'm wrong but it is used to determine which fields
are reads for projection push down.
In the case of self join (directly or indirectly) we end up with duplicate ids
in the same relation because the same field is derived to 2 different fields.
Otherwise I'm as lost as [~knoguchi] regarding the actual mechanisms around the
UID.
I tried to fix some of these in the past (PIG-3020) but it appears they created
more problems (PIG-3492)
[~daijy] maybe you can enlighten us?
> Store invocation brings side effect
> -----------------------------------
>
> Key: PIG-3347
> URL: https://issues.apache.org/jira/browse/PIG-3347
> Project: Pig
> Issue Type: Bug
> Components: grunt
> Affects Versions: 0.11
> Environment: local mode
> Reporter: Sergey
> Assignee: Daniel Dai
> Priority: Critical
> Fix For: 0.12.1
>
> Attachments: PIG-3347-1.patch
>
>
> The problem is that intermediate 'store' invocation "changes" the final store
> output. Looks like it brings some kind of side effect. We did use 'local'
> mode to run script
> here is the input data:
> 1
> 1
> Here is the script:
> {code}
> a = load 'test';
> a_group = group a by $0;
> b = foreach a_group {
> a_distinct = distinct a.$0;
> generate group, a_distinct;
> }
> --store b into 'b';
> c = filter b by SIZE(a_distinct) == 1;
> store c into 'out';
> {code}
> We expect output to be:
> 1 1
> The output is empty file.
> Uncomment {code}--store b into 'b';{code} line and see the diffrence.
> Yuo would get expected output.
--
This message was sent by Atlassian JIRA
(v6.1.5#6160)
