cloud-fan commented on a change in pull request #31368:
URL: https://github.com/apache/spark/pull/31368#discussion_r565816065
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/view.scala
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@@ -17,74 +17,21 @@
package org.apache.spark.sql.catalyst.analysis
-import org.apache.spark.sql.catalyst.expressions.Alias
-import org.apache.spark.sql.catalyst.plans.logical.{LogicalPlan, Project, View}
+import org.apache.spark.sql.catalyst.plans.logical.{LogicalPlan, View}
import org.apache.spark.sql.catalyst.rules.Rule
/**
* This file defines view types and analysis rules related to views.
*/
/**
- * This rule has two goals:
- *
- * 1. Removes [[View]] operators from the plan. The operator is respected till
the end of analysis
- * stage because we want to see which part of an analyzed logical plan is
generated from a view.
- *
- * 2. 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(This is mostly for handling view queries like SELECT
* FROM ..., the
- * schema of the referenced table/view may change after the view has
been created, so we
- * have to save the output of the query to `viewQueryColumnNames`, and
restore them during
- * view resolution, in this way, we are able to get the correct view
column ordering and
- * omit the extra columns that we don't require);
- * 1.2. Else set the child output attributes to `queryOutput`.
- * 2. Map the `queryOutput` 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.
- *
- * Once reaches this rule, it means `CheckAnalysis` did necessary checks on
number of columns
- * between the view output and the child output or the query column names.
`CheckAnalysis` also
- * checked the cast from the view's child to the Project is up-cast.
- *
- * This should be only done after the batch of Resolution, because the view
attributes are not
- * completely resolved during the batch of Resolution.
+ * This rule removes [[View]] operators from the plan. The operator is
respected till the end of
+ * analysis stage because we want to see which part of an analyzed logical
plan is generated from a
+ * view.
*/
object EliminateView extends Rule[LogicalPlan] with CastSupport {
override def apply(plan: LogicalPlan): LogicalPlan = plan transformUp {
Review comment:
seems doesn't matter?
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