GitHub user gatorsmile opened a pull request:
https://github.com/apache/spark/pull/14240
[SPARK-16594] [SQL] Remove Physical Plan Differences when Table Scan Having
Duplicate Columns
#### What changes were proposed in this pull request?
Currently, we keep two implementations for planning scans over data
sources. There is one difference between two implementation when deciding
whether a `Project` is needed or not.
- Data Source Table Scan:
https://github.com/apache/spark/blob/b1e5281c5cb429e338c3719c13c0b93078d7312a/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/DataSourceStrategy.scala#L322-L395
- `SELECT b, b FROM oneToTenPruned`: **_Add `ProjectExec`._**
- Hive Table Scan and In-memory Table Scan:
https://github.com/apache/spark/blob/865ec32dd997e63aea01a871d1c7b4947f43c111/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkPlanner.scala#L71-L99
- `SELECT b, b FROM oneToTenPruned`: **_No `ProjectExec` is added._**
**Note.** When alias is being used, we will always add `ProjectExec` in all
the scan types.
- `SELECT b as alias_b, b FROM oneToTenPruned`: **_Add `ProjectExec`._**
Because selecting the same column twice without adding `alias` is very
weird, no clue why the code needs to behave differently here. This PR is to
remove the differences.
#### How was this patch tested?
Updated/added a test case
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/gatorsmile/spark removeProject
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/14240.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #14240
----
commit ba7dcff8829c379666c417b87fc1e5022ed93141
Author: gatorsmile <[email protected]>
Date: 2016-07-17T07:26:47Z
fix
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