test: cast negative zero to string

[kazuyukitanimura]

Which issue does this PR close?

Closes #1036
Related #3811

Rationale for this change

The existing implementation is correct. This PR is for testing to confirm that.

The original analysis of #1036 is not quite right in my opinion, as I mentioned in #1036 (comment)

The real reason for #1036 is (at least in the current main branch) due to #3825

What changes are included in this PR?

How are these changes tested?

[andygrove]

@kazuyukitanimura Could you confirm the tests actually catch the negative zero case? The Rust format! macro still formats -0.0 as "-0.0" and I don't see a code change that normalizes it. It would be helpful to see the test output or add a more targeted assertion, for example a SQL file test like:

SELECT CAST(CAST('-0.0' AS FLOAT) AS STRING)

This would make it clear that Comet returns "0.0" rather than "-0.0". I tried this yesterday and saw an incompatibility that I wasn't able to fix easily.

[kazuyukitanimura]

Thanks @andygrove
The existing implementation is correct. This PR is for testing to confirm that.

The original analysis of #1036 is not quite right in my opinion, as I mentioned in #1036 (comment)

The real reason for #1036 is (at least in the current main branch) due to #3825

Could you confirm the tests actually catch the negative zero case?

Yes, it does. castTest runs the tests

The Rust format! macro still formats -0.0 as "-0.0" and I don't see a code change that normalizes it.

Spark does not normalize for casting float/double to String. You can quickly see that the following test passes.

  test("cast negative zeros") {
    withTable("t1") {
      Seq(0.0f, -0.0f, 0.0f, -0.0f).toDF("a").write.saveAsTable("t1")
      val df = sql("SELECT CAST(a AS STRING) FROM t1")
      checkSparkAnswerAndOperator(df)
    }
  }

It would be helpful to see the test output

The following is the printout of castTest

!== Correct Answer - 10013 ==    == Spark Answer - 10013 ==
 struct<a:float,a:string>        struct<a:float,a:string>
...
 [-0.0,-0.0]                     [-0.0,-0.0]
 [0.0,0.0]                       [0.0,0.0]
...

SELECT CAST(CAST('-0.0' AS FLOAT) AS STRING)

I do not think you meant this. CAST('-0.0' AS FLOAT) is not a part of this PR scope.

[andygrove]

Thanks @kazuyukitanimura. Yes, the original issue was incorrect.

[kazuyukitanimura]

Thank you @andygrove