Github user liancheng commented on a diff in the pull request:
https://github.com/apache/spark/pull/8049#discussion_r36664105
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/DataSourceStrategy.scala
---
@@ -410,6 +410,12 @@ private[sql] object DataSourceStrategy extends
Strategy with Logging {
case _ => None
}
- filters.flatMap(translate)
+ filters.map(eliminateCastOnAttribute(_)).flatMap(translate)
+ }
+
+ private def eliminateCastOnAttribute(expression: Expression): Expression
= {
+ expression.transform {
+ case Cast(a: Attribute, _) => a
+ }
--- End diff --
I haven't successfully constructed a test case to prove it, but simply
removing the casts here looks a little bit dangerous to me. For example, both
`BinaryOperator` and logic in `ParquetFilters` assume that both branches of a
binary expression should have the same data type.
Instead of removing the casts, how about transposing them? Namely,
converting
```
expression.transform {
case LessThan(Cast(a: Attribute, _), value) =>
LessThan(a, Cast(value, a.dataType).eval())
case LessThan(value, Cast(a: Attribute, _)) =>
LessThan(Cast(value, a.dataType).eval(), a)
...
}
```
In this way, we still ensure both branches have the same data type.
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