GitHub user gengliangwang opened a pull request:
https://github.com/apache/spark/pull/20278
[SPARK-23079][SQL]Fix query constraints propagation with aliases
## What changes were proposed in this pull request?
Previously, PR #19201 fix the problem of non-converging constraints.
After that PR #19149 improve the loop and constraints is inferred only once.
So the problem of non-converging constraints is gone.
However, the case below will fail.
```
spark.range(5).write.saveAsTable("t")
val t = spark.read.table("t")
val left = t.withColumn("xid", $"id" + lit(1)).as("x")
val right = t.withColumnRenamed("id", "xid").as("y")
val df = left.join(right, "xid").filter("id = 3").toDF()
checkAnswer(df, Row(4, 3))
```
Because `aliasMap` replace all the aliased child. See the test case in PR
for details.
This PR is to fix this bug by removing useless code for preventing
non-converging constraints.
It can be also fixed with #20270, but this is much simpler and clean up the
code.
## How was this patch tested?
Unit test
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/gengliangwang/spark FixConstraintSimple
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/20278.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 #20278
----
commit c02d9b4bdccafcdf4008dcdd4c2ad9509c9acd96
Author: Wang Gengliang <ltnwgl@...>
Date: 2018-01-16T17:05:28Z
Simple fix
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