Github user jiangxb1987 commented on a diff in the pull request:
https://github.com/apache/spark/pull/16561#discussion_r96168416
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/view.scala
---
@@ -28,22 +28,56 @@ import org.apache.spark.sql.catalyst.rules.Rule
*/
/**
- * Make sure that a view's child plan produces the view's output
attributes. We wrap the child
- * with a Project and add an alias for each output attribute. The
attributes are resolved by
- * name. This should be only done after the batch of Resolution, because
the view attributes are
- * not completely resolved during the batch of Resolution.
+ * Make sure that a view's child plan produces the view's output
attributes. We try to wrap the
+ * child by:
+ * 1. Generate the `queryOutput` by:
+ * 1.1. If the query column names are defined, map the column names to
attributes in the child
+ * output by name;
+ * 1.2. Else set the child output attributes to `queryOutput`.
+ * 2. Map the `queryQutput` to view output by index, if the corresponding
attributes don't match,
+ * try to up cast and alias the attribute in `queryOutput` to the
attribute in the view output.
+ * 3. Add a Project over the child, with the new output generated by the
previous steps.
+ * If the view output doesn't have the same number of columns neither with
the child output, nor
+ * with the query column names, throw an AnalysisException.
+ *
+ * This should be only done after the batch of Resolution, because the
view attributes are not
+ * completely resolved during the batch of Resolution.
*/
case class AliasViewChild(conf: CatalystConf) extends Rule[LogicalPlan] {
override def apply(plan: LogicalPlan): LogicalPlan = plan
resolveOperators {
- case v @ View(_, output, child) if child.resolved =>
+ case v @ View(desc, output, child) if child.resolved =>
val resolver = conf.resolver
- val newOutput = output.map { attr =>
- val originAttr = findAttributeByName(attr.name, child.output,
resolver)
- // The dataType of the output attributes may be not the same with
that of the view output,
- // so we should cast the attribute to the dataType of the view
output attribute. If the
- // cast can't perform, will throw an AnalysisException.
- Alias(Cast(originAttr, attr.dataType), attr.name)(exprId =
attr.exprId,
- qualifier = attr.qualifier, explicitMetadata =
Some(attr.metadata))
+ val queryColumnNames = desc.viewQueryColumnNames
+ // If the view output doesn't have the same number of columns with
the child output and the
+ // query column names, throw an AnalysisException.
+ if (output.length != child.output.length && output.length !=
queryColumnNames.length) {
+ throw new AnalysisException(
+ s"The view output ${output.mkString("[", ",", "]")} doesn't have
the same number of " +
+ s"columns with the child output ${child.output.mkString("[",
",", "]")}")
+ }
+ // If the child output is the same with the view output, we don't
need to generate the query
+ // output again.
+ val queryOutput = if (queryColumnNames.nonEmpty && output !=
child.output) {
--- End diff --
For a nested view, the inner view operator may have been resolved, in that
case the output is the same with child.output.
---
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