[GitHub] [spark] hvanhovell commented on a change in pull request #22573: [SPARK-25558][SQL] Pushdown predicates for nested fields in DataSource Strategy

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hvanhovell commented on a change in pull request #22573: [SPARK-25558][SQL] Pushdown predicates for nested fields in DataSource Strategy
URL: https://github.com/apache/spark/pull/22573#discussion_r275846248
 
 

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 File path: sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/DataSourceStrategy.scala
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 @@ -442,53 +442,65 @@ object DataSourceStrategy {
    * @return a `Some[Filter]` if the input [[Expression]] is convertible, otherwise a `None`.
    */
   protected[sql] def translateFilter(predicate: Expression): Option[Filter] = {
+    // Recursively try to find an attribute name from the top level that can be pushed down.
+    def attrName(e: Expression): Option[String] = e match {
+      // In Spark and many data sources such as parquet, dots are used as a column path delimiter;
+      // thus, we don't translate such expressions.
+      case a: Attribute if !a.name.contains(".") =>
+        Some(a.name)
+      case s: GetStructField if !s.childSchema(s.ordinal).name.contains(".") =>
+        attrName(s.child).map(_ + s".${s.childSchema(s.ordinal).name}")
 
 Review comment:
   `_ + "." + s.childSchema(s.ordinal).name`?

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