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https://issues.apache.org/jira/browse/TAJO-1832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14903086#comment-14903086
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ASF GitHub Bot commented on TAJO-1832:
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Github user jihoonson commented on the pull request:
https://github.com/apache/tajo/pull/756#issuecomment-142364353
Thank you for your review.
As the answer for your question, the ```already known information``` has a
higher priority. For example, if the nested column name of a table of
self-describing format has the same name with a database or a table, the
database name (or the table name) has a higher priority than nested column name
because it is already known information.
However, the table has a predefined schema, NameResolver follows the
existing routine even though the query involves a column of nested type.
> Well support for self-describing data formats
> ---------------------------------------------
>
> Key: TAJO-1832
> URL: https://issues.apache.org/jira/browse/TAJO-1832
> Project: Tajo
> Issue Type: New Feature
> Components: Planner/Optimizer
> Reporter: Jihoon Son
> Assignee: Jihoon Son
>
> *Problem*
> Tajo already has a support for self-describing data formats like JSON,
> Parquet, or ORC. While they are capable of providing schema information by
> themselves, users must define schema to query on them with the current
> implementation. To solve this inconvenience, we have to improve our query
> planner to support self-describing data formats well.
> *Solution*
> First, we need to allow omitting schema definition for the create table
> statement. When a query is submitted for a self-describing table, the columns
> which don't exist in that table will be filled with Nulls.
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