[SPARK-15234][SQL] Fix spark.catalog.listDatabases.show()

## What changes were proposed in this pull request?

Before:
```
scala> spark.catalog.listDatabases.show()
+--------------------+-----------+-----------+
|                name|description|locationUri|
+--------------------+-----------+-----------+
|Database[name='de...|
|Database[name='my...|
|Database[name='so...|
+--------------------+-----------+-----------+
```

After:
```
+-------+--------------------+--------------------+
|   name|         description|         locationUri|
+-------+--------------------+--------------------+
|default|Default Hive data...|file:/user/hive/w...|
|  my_db|  This is a database|file:/Users/andre...|
|some_db|                    |file:/private/var...|
+-------+--------------------+--------------------+
```

## How was this patch tested?

New test in `CatalogSuite`

Author: Andrew Or <andrew@databricks.com>

Closes #13015 from andrewor14/catalog-show.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/ScalaReflection.scala

@@ -17,7 +17,6 @@
 
 package org.apache.spark.sql.catalyst
 
-import org.apache.spark.SparkException
 import org.apache.spark.sql.catalyst.analysis.{UnresolvedAttribute, UnresolvedExtractValue}
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.util.{ArrayBasedMapData, DateTimeUtils, GenericArrayData}
@@ -659,6 +658,15 @@ object ScalaReflection extends ScalaReflection {
     constructParams(t).map(_.name.toString)
   }
 
+  /**
+   * Returns the parameter values for the primary constructor of this class.
+   */
+  def getConstructorParameterValues(obj: DefinedByConstructorParams): Seq[AnyRef] = {
+    getConstructorParameterNames(obj.getClass).map { name =>
+      obj.getClass.getMethod(name).invoke(obj)
+    }
+  }
+
   /*
    * Retrieves the runtime class corresponding to the provided type.
    */

sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala

@@ -245,6 +245,8 @@ class Dataset[T] private[sql](
     val rows: Seq[Seq[String]] = schema.fieldNames.toSeq +: data.map {
       case r: Row => r
       case tuple: Product => Row.fromTuple(tuple)
+      case definedByCtor: DefinedByConstructorParams =>
+        Row.fromSeq(ScalaReflection.getConstructorParameterValues(definedByCtor))
       case o => Row(o)
     }.map { row =>
       row.toSeq.map { cell =>

sql/core/src/main/scala/org/apache/spark/sql/internal/CatalogImpl.scala

@@ -50,14 +50,6 @@ class CatalogImpl(sparkSession: SparkSession) extends Catalog {
     }
   }
 
-  private def makeDataset[T <: DefinedByConstructorParams: TypeTag](data: Seq[T]): Dataset[T] = {
-    val enc = ExpressionEncoder[T]()
-    val encoded = data.map(d => enc.toRow(d).copy())
-    val plan = new LocalRelation(enc.schema.toAttributes, encoded)
-    val queryExecution = sparkSession.executePlan(plan)
-    new Dataset[T](sparkSession, queryExecution, enc)
-  }
-
   /**
    * Returns the current default database in this session.
    */
@@ -83,7 +75,7 @@ class CatalogImpl(sparkSession: SparkSession) extends Catalog {
         description = metadata.description,
         locationUri = metadata.locationUri)
     }
-    makeDataset(databases)
+    CatalogImpl.makeDataset(databases, sparkSession)
   }
 
   /**
@@ -111,7 +103,7 @@ class CatalogImpl(sparkSession: SparkSession) extends Catalog {
         tableType = metadata.map(_.tableType.name).getOrElse("TEMPORARY"),
         isTemporary = isTemp)
     }
-    makeDataset(tables)
+    CatalogImpl.makeDataset(tables, sparkSession)
   }
 
   /**
@@ -137,7 +129,7 @@ class CatalogImpl(sparkSession: SparkSession) extends Catalog {
         className = metadata.getClassName,
         isTemporary = funcIdent.database.isEmpty)
     }
-    makeDataset(functions)
+    CatalogImpl.makeDataset(functions, sparkSession)
   }
 
   /**
@@ -166,7 +158,7 @@ class CatalogImpl(sparkSession: SparkSession) extends Catalog {
         isPartition = partitionColumnNames.contains(c.name),
         isBucket = bucketColumnNames.contains(c.name))
     }
-    makeDataset(columns)
+    CatalogImpl.makeDataset(columns, sparkSession)
   }
 
   /**
@@ -350,3 +342,18 @@ class CatalogImpl(sparkSession: SparkSession) extends Catalog {
   }
 
 }
+
+
+private[sql] object CatalogImpl {
+
+  def makeDataset[T <: DefinedByConstructorParams: TypeTag](
+      data: Seq[T],
+      sparkSession: SparkSession): Dataset[T] = {
+    val enc = ExpressionEncoder[T]()
+    val encoded = data.map(d => enc.toRow(d).copy())
+    val plan = new LocalRelation(enc.schema.toAttributes, encoded)
+    val queryExecution = sparkSession.executePlan(plan)
+    new Dataset[T](sparkSession, queryExecution, enc)
+  }
+
+}

sql/core/src/test/scala/org/apache/spark/sql/internal/CatalogSuite.scala

@@ -22,7 +22,7 @@ import org.scalatest.BeforeAndAfterEach
 import org.apache.spark.SparkFunSuite
 import org.apache.spark.sql.{AnalysisException, SparkSession}
 import org.apache.spark.sql.catalog.{Column, Database, Function, Table}
-import org.apache.spark.sql.catalyst.{FunctionIdentifier, TableIdentifier}
+import org.apache.spark.sql.catalyst.{FunctionIdentifier, ScalaReflection, TableIdentifier}
 import org.apache.spark.sql.catalyst.catalog._
 import org.apache.spark.sql.catalyst.expressions.{Expression, ExpressionInfo}
 import org.apache.spark.sql.catalyst.plans.logical.Range
@@ -266,6 +266,30 @@ class CatalogSuite
         "nullable='false', isPartition='true', isBucket='true']")
   }
 
+  test("catalog classes format in Dataset.show") {
+    val db = new Database("nama", "descripta", "locata")
+    val table = new Table("nama", "databasa", "descripta", "typa", isTemporary = false)
+    val function = new Function("nama", "descripta", "classa", isTemporary = false)
+    val column = new Column(
+      "nama", "descripta", "typa", nullable = false, isPartition = true, isBucket = true)
+    val dbFields = ScalaReflection.getConstructorParameterValues(db)
+    val tableFields = ScalaReflection.getConstructorParameterValues(table)
+    val functionFields = ScalaReflection.getConstructorParameterValues(function)
+    val columnFields = ScalaReflection.getConstructorParameterValues(column)
+    assert(dbFields == Seq("nama", "descripta", "locata"))
+    assert(tableFields == Seq("nama", "databasa", "descripta", "typa", false))
+    assert(functionFields == Seq("nama", "descripta", "classa", false))
+    assert(columnFields == Seq("nama", "descripta", "typa", false, true, true))
+    val dbString = CatalogImpl.makeDataset(Seq(db), sparkSession).showString(10)
+    val tableString = CatalogImpl.makeDataset(Seq(table), sparkSession).showString(10)
+    val functionString = CatalogImpl.makeDataset(Seq(function), sparkSession).showString(10)
+    val columnString = CatalogImpl.makeDataset(Seq(column), sparkSession).showString(10)
+    dbFields.foreach { f => assert(dbString.contains(f.toString)) }
+    tableFields.foreach { f => assert(tableString.contains(f.toString)) }
+    functionFields.foreach { f => assert(functionString.contains(f.toString)) }
+    columnFields.foreach { f => assert(columnString.contains(f.toString)) }
+  }
+
   // TODO: add tests for the rest of them
 
 }