brkyvz commented on a change in pull request #27350: [SPARK-30615][SQL]
Introduce Analyzer rule for V2 AlterTable column change resolution
URL: https://github.com/apache/spark/pull/27350#discussion_r373093861
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
##########
@@ -3002,6 +3004,161 @@ class Analyzer(
}
}
}
+
+ /** Rule to mostly resolve, normalize and rewrite column names based on case
sensitivity. */
+ object ResolveAlterTableChanges extends Rule[LogicalPlan] {
+ def apply(plan: LogicalPlan): LogicalPlan = plan.resolveOperatorsUp {
+ case a @ AlterTable(_, _, t: NamedRelation, changes) if t.resolved =>
+ val schema = t.schema
+ val normalizedChanges = changes.flatMap {
+ case add: AddColumn =>
+ val parent = add.fieldNames().init
+ if (parent.nonEmpty) {
+ // Adding a nested field, need to normalize the parent column
and position
+ val target = schema.findNestedField(parent, includeCollections =
true, conf.resolver)
+ if (target.isEmpty) {
+ // Leave unresolved. Throws error in CheckAnalysis
+ Some(add)
+ } else {
+ val (normalizedName, sf) = target.get
+ sf.dataType match {
+ case struct: StructType =>
+ val pos = findColumnPosition(add.position(),
parent.quoted, struct)
+ Some(TableChange.addColumn(
+ (normalizedName ++ Seq(sf.name,
add.fieldNames().last)).toArray,
+ add.dataType(),
+ add.isNullable,
+ add.comment,
+ pos))
+
+ case other =>
+ throw new AnalysisException(
+ s"Columns can only be added to struct types. Found
${other.simpleString}.")
+ }
+ }
+ } else {
+ // Adding to the root. Just need to normalize position
+ val pos = findColumnPosition(add.position(), "root", schema)
+ Some(TableChange.addColumn(
+ add.fieldNames(),
+ add.dataType(),
+ add.isNullable,
+ add.comment,
+ pos))
+ }
+
+ case typeChange: UpdateColumnType =>
+ // Hive style syntax provides the column type, even if it may not
have changed
+ val fieldOpt = schema.findNestedField(
+ typeChange.fieldNames(), includeCollections = true,
conf.resolver)
+
+ if (fieldOpt.isEmpty) {
+ // We couldn't resolve the field. Leave it to CheckAnalysis
+ Some(typeChange)
+ } else {
+ val (fieldNames, field) = fieldOpt.get
+ if (field.dataType == typeChange.newDataType()) {
+ // The user didn't want the field to change, so remove this
change
+ None
+ } else {
+ Some(TableChange.updateColumnType(
+ (fieldNames :+ field.name).toArray,
typeChange.newDataType()))
+ }
+ }
+ case n: UpdateColumnNullability =>
+ // Need to resolve column
+ resolveFieldNames(
+ schema,
+ n.fieldNames(),
+ TableChange.updateColumnNullability(_,
n.nullable())).orElse(Some(n))
+
+ case position: UpdateColumnPosition =>
+ position.position() match {
+ case after: After =>
+ // Need to resolve column as well as position reference
+ val fieldOpt = schema.findNestedField(
+ position.fieldNames(), includeCollections = true,
conf.resolver)
+
+ if (fieldOpt.isEmpty) {
+ Some(position)
+ } else {
+ val (normalizedPath, field) = fieldOpt.get
+ val targetCol = schema.findNestedField(
+ normalizedPath :+ after.column(), includeCollections =
true, conf.resolver)
+ if (targetCol.isEmpty) {
+ // Leave unchanged to CheckAnalysis
+ Some(position)
+ } else {
+ Some(TableChange.updateColumnPosition(
+ (normalizedPath :+ field.name).toArray,
+ ColumnPosition.after(targetCol.get._2.name)))
+ }
+ }
+ case _ =>
+ // Need to resolve column
+ resolveFieldNames(
+ schema,
+ position.fieldNames(),
+ TableChange.updateColumnPosition(_,
position.position())).orElse(Some(position))
+ }
+
+ case comment: UpdateColumnComment =>
+ resolveFieldNames(
+ schema,
+ comment.fieldNames(),
+ TableChange.updateColumnComment(_,
comment.newComment())).orElse(Some(comment))
+
+ case rename: RenameColumn =>
+ resolveFieldNames(
+ schema,
+ rename.fieldNames(),
+ TableChange.renameColumn(_,
rename.newName())).orElse(Some(rename))
+
+ case delete: DeleteColumn =>
+ resolveFieldNames(schema, delete.fieldNames(),
TableChange.deleteColumn)
+ .orElse(Some(delete))
+
+ case column: ColumnChange =>
+ // This is informational for future developers
+ throw new UnsupportedOperationException(
+ "Please add an implementation for a column change here")
+ case other => Some(other)
+ }
+
+ a.copy(changes = normalizedChanges)
+ }
+
+ /**
+ * Returns the table change if the field can be resolved, returns None if
the column is not
+ * found. An error will be thrown in CheckAnalysis for columns that can't
be resolved.
+ */
+ private def resolveFieldNames(
+ schema: StructType,
+ fieldNames: Array[String],
+ copy: Array[String] => TableChange): Option[TableChange] = {
+ val fieldOpt = schema.findNestedField(
+ fieldNames, includeCollections = true, conf.resolver)
+ fieldOpt.map { case (path, field) => copy((path :+ field.name).toArray) }
+ }
+
+ private def findColumnPosition(
+ position: ColumnPosition,
+ field: String,
+ struct: StructType): ColumnPosition = {
+ position match {
+ case null => null
Review comment:
when you're adding a column without a position (so to the end)
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