[SPARK-17180][SPARK-17309][SPARK-17323][SQL] create AlterViewAsCommand to handle ALTER VIEW AS

## What changes were proposed in this pull request?

Currently we use `CreateViewCommand` to implement ALTER VIEW AS, which has 3 bugs:

1. SPARK-17180: ALTER VIEW AS should alter temp view if view name has no database part and temp view exists
2. SPARK-17309: ALTER VIEW AS should issue exception if view does not exist.
3. SPARK-17323: ALTER VIEW AS should keep the previous table properties, comment, create_time, etc.

The root cause is, ALTER VIEW AS is quite different from CREATE VIEW, we need different code path to handle them. However, in `CreateViewCommand`, there is no way to distinguish ALTER VIEW AS and CREATE VIEW, we have to introduce extra flag. But instead of doing this, I think a more natural way is to separate the ALTER VIEW AS logic into a new command.

## How was this patch tested?

new tests in SQLViewSuite

Author: Wenchen Fan <wenchen@databricks.com>

Closes #14874 from cloud-fan/minor4.

2 files changed, 83 insertions, 57 deletions

diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkSqlParser.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkSqlParser.scala
index e32d30178e..656494d97d 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkSqlParser.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkSqlParser.scala
@@ -1254,60 +1254,33 @@ class SparkSqlAstBuilder(conf: SQLConf) extends AstBuilder {
           ic.identifier.getText -> Option(ic.STRING).map(string)
         }
       }
-      createView(
-        ctx,
-        ctx.tableIdentifier,
+
+      CreateViewCommand(
+        name = visitTableIdentifier(ctx.tableIdentifier),
+        userSpecifiedColumns = userSpecifiedColumns,
         comment = Option(ctx.STRING).map(string),
-        userSpecifiedColumns,
-        ctx.query,
-        Option(ctx.tablePropertyList).map(visitPropertyKeyValues).getOrElse(Map.empty),
+        properties = Option(ctx.tablePropertyList).map(visitPropertyKeyValues).getOrElse(Map.empty),
+        originalText = Option(source(ctx.query)),
+        child = plan(ctx.query),
         allowExisting = ctx.EXISTS != null,
         replace = ctx.REPLACE != null,
-        isTemporary = ctx.TEMPORARY != null
-      )
+        isTemporary = ctx.TEMPORARY != null)
     }
   }
 
   /**
-   * Alter the query of a view. This creates a [[CreateViewCommand]] command.
+   * Alter the query of a view. This creates a [[AlterViewAsCommand]] command.
+   *
+   * For example:
+   * {{{
+   *   ALTER VIEW [db_name.]view_name AS SELECT ...;
+   * }}}
    */
   override def visitAlterViewQuery(ctx: AlterViewQueryContext): LogicalPlan = withOrigin(ctx) {
-    createView(
-      ctx,
-      name = ctx.tableIdentifier,
-      comment = None,
-      userSpecifiedColumns = Seq.empty,
-      query = ctx.query,
-      properties = Map.empty,
-      allowExisting = false,
-      replace = true,
-      isTemporary = false)
-  }
-
-  /**
-   * Create a [[CreateViewCommand]] command.
-   */
-  private def createView(
-      ctx: ParserRuleContext,
-      name: TableIdentifierContext,
-      comment: Option[String],
-      userSpecifiedColumns: Seq[(String, Option[String])],
-      query: QueryContext,
-      properties: Map[String, String],
-      allowExisting: Boolean,
-      replace: Boolean,
-      isTemporary: Boolean): LogicalPlan = {
-    val originalText = source(query)
-    CreateViewCommand(
-      visitTableIdentifier(name),
-      userSpecifiedColumns,
-      comment,
-      properties,
-      Some(originalText),
-      plan(query),
-      allowExisting = allowExisting,
-      replace = replace,
-      isTemporary = isTemporary)
+    AlterViewAsCommand(
+      name = visitTableIdentifier(ctx.tableIdentifier),
+      originalText = source(ctx.query),
+      query = plan(ctx.query))
   }
 
   /**
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/command/views.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/command/views.scala
index f0d7b64c3c..15340ee921 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/command/views.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/command/views.scala
@@ -22,15 +22,16 @@ import scala.util.control.NonFatal
 import org.apache.spark.sql.{AnalysisException, Row, SparkSession}
 import org.apache.spark.sql.catalyst.{SQLBuilder, TableIdentifier}
 import org.apache.spark.sql.catalyst.catalog.{CatalogStorageFormat, CatalogTable, CatalogTableType}
-import org.apache.spark.sql.catalyst.expressions.{Alias, Attribute}
+import org.apache.spark.sql.catalyst.expressions.Alias
 import org.apache.spark.sql.catalyst.plans.QueryPlan
 import org.apache.spark.sql.catalyst.plans.logical.{LogicalPlan, Project}
 import org.apache.spark.sql.types.StructType
 
 
 /**
- * Create Hive view on non-hive-compatible tables by specifying schema ourselves instead of
- * depending on Hive meta-store.
+ * Create or replace a view with given query plan. This command will convert the query plan to
+ * canonicalized SQL string, and store it as view text in metastore, if we need to create a
+ * permanent view.
  *
  * @param name the name of this view.
  * @param userSpecifiedColumns the output column names and optional comments specified by users,
@@ -64,11 +65,6 @@ case class CreateViewCommand(
 
   override protected def innerChildren: Seq[QueryPlan[_]] = Seq(child)
 
-  // TODO: Note that this class can NOT canonicalize the view SQL string entirely, which is
-  // different from Hive and may not work for some cases like create view on self join.
-
-  override def output: Seq[Attribute] = Seq.empty[Attribute]
-
   if (!isTemporary) {
     require(originalText.isDefined,
       "The table to created with CREATE VIEW must have 'originalText'.")
@@ -119,9 +115,7 @@ case class CreateViewCommand(
           // Handles `CREATE VIEW IF NOT EXISTS v0 AS SELECT ...`. Does nothing when the target view
           // already exists.
         } else if (tableMetadata.tableType != CatalogTableType.VIEW) {
-          throw new AnalysisException(
-            "Existing table is not a view. The following is an existing table, " +
-              s"not a view: $qualifiedName")
+          throw new AnalysisException(s"$qualifiedName is not a view")
         } else if (replace) {
           // Handles `CREATE OR REPLACE VIEW v0 AS SELECT ...`
           sessionState.catalog.alterTable(prepareTable(sparkSession, analyzedPlan))
@@ -179,7 +173,7 @@ case class CreateViewCommand(
       sparkSession.sql(viewSQL).queryExecution.assertAnalyzed()
     } catch {
       case NonFatal(e) =>
-        throw new RuntimeException(s"Failed to analyze the canonicalized SQL: ${viewSQL}", e)
+        throw new RuntimeException(s"Failed to analyze the canonicalized SQL: $viewSQL", e)
     }
 
     val viewSchema = if (userSpecifiedColumns.isEmpty) {
@@ -202,3 +196,62 @@ case class CreateViewCommand(
     )
   }
 }
+
+/**
+ * Alter a view with given query plan. If the view name contains database prefix, this command will
+ * alter a permanent view matching the given name, or throw an exception if view not exist. Else,
+ * this command will try to alter a temporary view first, if view not exist, try permanent view
+ * next, if still not exist, throw an exception.
+ *
+ * @param name the name of this view.
+ * @param originalText the original SQL text of this view. Note that we can only alter a view by
+ *                     SQL API, which means we always have originalText.
+ * @param query the logical plan that represents the view; this is used to generate a canonicalized
+ *              version of the SQL that can be saved in the catalog.
+ */
+case class AlterViewAsCommand(
+    name: TableIdentifier,
+    originalText: String,
+    query: LogicalPlan) extends RunnableCommand {
+
+  override protected def innerChildren: Seq[QueryPlan[_]] = Seq(query)
+
+  override def run(session: SparkSession): Seq[Row] = {
+    // If the plan cannot be analyzed, throw an exception and don't proceed.
+    val qe = session.sessionState.executePlan(query)
+    qe.assertAnalyzed()
+    val analyzedPlan = qe.analyzed
+
+    if (session.sessionState.catalog.isTemporaryTable(name)) {
+      session.sessionState.catalog.createTempView(name.table, analyzedPlan, overrideIfExists = true)
+    } else {
+      alterPermanentView(session, analyzedPlan)
+    }
+
+    Seq.empty[Row]
+  }
+
+  private def alterPermanentView(session: SparkSession, analyzedPlan: LogicalPlan): Unit = {
+    val viewMeta = session.sessionState.catalog.getTableMetadata(name)
+    if (viewMeta.tableType != CatalogTableType.VIEW) {
+      throw new AnalysisException(s"${viewMeta.identifier} is not a view.")
+    }
+
+    val viewSQL: String = new SQLBuilder(analyzedPlan).toSQL
+    // Validate the view SQL - make sure we can parse it and analyze it.
+    // If we cannot analyze the generated query, there is probably a bug in SQL generation.
+    try {
+      session.sql(viewSQL).queryExecution.assertAnalyzed()
+    } catch {
+      case NonFatal(e) =>
+        throw new RuntimeException(s"Failed to analyze the canonicalized SQL: $viewSQL", e)
+    }
+
+    val updatedViewMeta = viewMeta.copy(
+      schema = analyzedPlan.schema,
+      viewOriginalText = Some(originalText),
+      viewText = Some(viewSQL))
+
+    session.sessionState.catalog.alterTable(updatedViewMeta)
+  }
+}