[GitHub] [spark] viirya commented on a change in pull request #31993: [SPARK-34897][SQL] Support reconcile schemas based on index after nested column pruning

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viirya commented on a change in pull request #31993:
URL: https://github.com/apache/spark/pull/31993#discussion_r614488314



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/SchemaPruning.scala
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@@ -21,9 +21,12 @@ import org.apache.spark.sql.types._
 
 object SchemaPruning {
   /**
-   * Filters the schema by the requested fields. For example, if the schema is struct<a:int, b:int>,
-   * and given requested field are "a", the field "b" is pruned in the returned schema.
-   * Note that schema field ordering at original schema is still preserved in pruned schema.
+   * Prunes the nested schema by the requested fields. For example, if the schema is
+   * struct<a:int, b:int>, and given requested field are "a", the field "b" is pruned in the
+   * returned schema.
+   * Note that:
+   *   1. The schema field ordering at original schema is still preserved in pruned schema.
+   *   2. The top-level fields are not pruned here.

Review comment:
       Hmm, doesn't it mean we miss the change to prune top-level columns?




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