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https://issues.apache.org/jira/browse/PIG-833?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12745770#action_12745770
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He Yongqiang commented on PIG-833:
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Thanks Jing.
Yeah, i know the design of column groups and projection.
The reason i was asking is that i saw an usage in line 251 TestBasicTable.java:
{noformat}
doReadWrite(path, 2, 100, "SF_a,SF_b,SF_c,SF_d,SF_e",
"[SF_a,SF_b,SF_c];[SF_d,SF_e]", "SF_f,SF_a,SF_c,SF_d", true, false);
{noformat}
where "SF_f,SF_a,SF_c,SF_d" is passed as projection, but is there a column
"SF_f" defined?
btw, can you give more detail about the design of Partition? ColumnGroup is
much like projection in C-Store, so it can be more easily to be understood.
> Storage access layer
> --------------------
>
> Key: PIG-833
> URL: https://issues.apache.org/jira/browse/PIG-833
> Project: Pig
> Issue Type: New Feature
> Reporter: Jay Tang
> Attachments: hadoop20.jar.bz2, PIG-833-zebra.patch,
> PIG-833-zebra.patch.bz2, PIG-833-zebra.patch.bz2,
> TEST-org.apache.hadoop.zebra.pig.TestCheckin1.txt, test.out, zebra-javadoc.tgz
>
>
> A layer is needed to provide a high level data access abstraction and a
> tabular view of data in Hadoop, and could free Pig users from implementing
> their own data storage/retrieval code. This layer should also include a
> columnar storage format in order to provide fast data projection,
> CPU/space-efficient data serialization, and a schema language to manage
> physical storage metadata. Eventually it could also support predicate
> pushdown for further performance improvement. Initially, this layer could be
> a contrib project in Pig and become a hadoop subproject later on.
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