[GitHub] [spark] imback82 commented on a change in pull request #31440: [SPARK-34331][SQL] Speed up DS v2 metadata col resolution

[GitBox <gi...@apache.org>]

imback82 commented on a change in pull request #31440:
URL: https://github.com/apache/spark/pull/31440#discussion_r568839896



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
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@@ -4034,3 +4009,37 @@ object ApplyCharTypePadding extends Rule[LogicalPlan] {
     if (targetLength > charLength) StringRPad(expr, Literal(targetLength)) else expr
   }
 }
+
+/**
+ * This rule removes metadata columns from `DataSourceV2Relation` under 2 cases:
+ *   - A single v2 scan (can be produced by `spark.table`), which is similar to star expansion, and
+ *     metadata columns should only be picked by explicit references.
+ *   - V2 scans under writing commands, as we can't insert into metadata columns.
+ */
+object RemoveMetadataColumns extends Rule[LogicalPlan] {
+  import org.apache.spark.sql.execution.datasources.v2.DataSourceV2Implicits._
+
+  private def removeMetaCol(tbl: NamedRelation): NamedRelation = tbl match {
+    case r: DataSourceV2Relation =>
+      if (r.output.exists(_.isMetadataCol)) {
+        r.copy(output = r.output.filterNot(_.isMetadataCol))
+      } else {
+        r
+      }
+    case _ => tbl
+  }
+
+  override def apply(plan: LogicalPlan): LogicalPlan = plan match {
+    case r: DataSourceV2Relation => removeMetaCol(r)
+    case s @ SubqueryAlias(_, r: DataSourceV2Relation) => s.copy(child = removeMetaCol(r))
+    case _ => plan.resolveOperators {
+      case i: InsertIntoStatement => i.copy(i.table match {
+        case r: DataSourceV2Relation => removeMetaCol(r)
+        case other => other
+      })
+      case a: AppendData => a.withNewTable(removeMetaCol(a.table))
+      case o: OverwriteByExpression => o.withNewTable(removeMetaCol(o.table))
+      case o: OverwritePartitionsDynamic => o.withNewTable(removeMetaCol(o.table))

Review comment:
       Can these be replaced with `case v: V2WriteCommand => v.withNewTable(removeMetaCol(v.table))`, or do we need to match these specific types?




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