cloud-fan commented on pull request #21852:
URL: https://github.com/apache/spark/pull/21852#issuecomment-722823667
@wangyum this looks correct. After `SELECT *, rand(100) as rd FROM t`, the
output column `rd` is deterministic, as the result of `rand(100)` is
materialized. We can treat it like writing `SELECT *, rand(100) as rd FROM t`
to a table and read back.
However, I do see a problem:
```
scala> sql("select 1 FROM (SELECT *, rand(100) as rd FROM t) t1").explain
== Physical Plan ==
*(1) Project [1 AS 1#4]
+- FileScan json default.t[] Batched: false, DataFilters: [], Format: JSON,
Location:
InMemoryFileIndex[file:/Users/cloud0fan/dev/spark/assembly/spark-warehouse/t],
PartitionFilters: [], PushedFilters: [], ReadSchema: struct<>
```
Seems we shouldn't eliminate the project with `rand(100)`. But it's not
related to this PR.
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