[SPARK-46632][SQL] EquivalentExpressions addExprTree should allow all type of expressions

[planga82]

What changes were proposed in this pull request?

When we try to add some expressions to equivalent expressions it fail

import org.apache.spark.sql.catalyst.dsl.expressions.DslExpression
import org.apache.spark.sql.catalyst.expressions.{EquivalentExpressions, If, Literal}
import org.apache.spark.sql.functions.col

val one = Literal(1.0)
val y = col("y").expr
val e1 = If(
  Literal(true),
  y * one * one + one * one * y,
  y * one * one + one * one * y
)
(new EquivalentExpressions).addExprTree(e1)

java.lang.IllegalStateException: Cannot update expression: (1.0 * 1.0) in map: Map(ExpressionEquals(('y * 1.0)) -> ExpressionStats(('y * 1.0))) with use count: -1
  at org.apache.spark.sql.catalyst.expressions.EquivalentExpressions.updateExprInMap(EquivalentExpressions.scala:85)
  at org.apache.spark.sql.catalyst.expressions.EquivalentExpressions.updateExprTree(EquivalentExpressions.scala:198)
  at org.apache.spark.sql.catalyst.expressions.EquivalentExpressions.$anonfun$updateExprTree$1(EquivalentExpressions.scala:200)
  at org.apache.spark.sql.catalyst.expressions.EquivalentExpressions.$anonfun$updateExprTree$1$adapted(EquivalentExpressions.scala:200)
  at scala.collection.Iterator.foreach(Iterator.scala:943)
  at scala.collection.Iterator.foreach$(Iterator.scala:943)
  at scala.collection.AbstractIterator.foreach(Iterator.scala:1431)
...

The main problem is when updateExprTree is used with useCount = 1 it iterates through the children of an expression in a certain order. When in updateExprInMap an equivalent (but not equal) expression is found, it does not iterate over its children. Therefore to be able to perform the inverse operation (useCount = -1) it is necessary to traverse the children in inverse order how they were added because the children of two equivalent expressions are not necessarily equal, as the example that we have (y + 1) + 1 is equivalent to (1 + 1) + y but (y + 1) is not equal to (1 + 1).

Why are the changes needed?

To fix an issue with some type of expressions

Does this PR introduce any user-facing change?

No

How was this patch tested?

Unit testing

Was this patch authored or co-authored using generative AI tooling?

No

[planga82]

CC @viirya

[zml1206]

Reverse does not seem to solve the problem, for example:

Seq((1, 2, 3), (2, 3, 4)).toDF("a", "b", "c")
      .selectExpr("case when a + b + c>3 then 1" +
        " when c + a + b>10 then 2 else 0 end as d").show()

[planga82]

Thank you @zml1206 . I saw that you have proposed other solution. I'm going to close this PR