[SPARK-17150][SQL] Support SQL generation for inline tables

## What changes were proposed in this pull request?
This patch adds support for SQL generation for inline tables. With this, it would be possible to create a view that depends on inline tables.

## How was this patch tested?
Added a test case in LogicalPlanToSQLSuite.

Author: petermaxlee <petermaxlee@gmail.com>

Closes #14709 from petermaxlee/SPARK-17150.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LocalRelation.scala

@@ -18,8 +18,9 @@
 package org.apache.spark.sql.catalyst.plans.logical
 
 import org.apache.spark.sql.Row
-import org.apache.spark.sql.catalyst.{analysis, CatalystTypeConverters, InternalRow}
-import org.apache.spark.sql.catalyst.expressions.Attribute
+import org.apache.spark.sql.catalyst.{CatalystTypeConverters, InternalRow}
+import org.apache.spark.sql.catalyst.analysis
+import org.apache.spark.sql.catalyst.expressions.{Attribute, Literal}
 import org.apache.spark.sql.types.{StructField, StructType}
 
 object LocalRelation {
@@ -75,4 +76,16 @@ case class LocalRelation(output: Seq[Attribute], data: Seq[InternalRow] = Nil)
 
   override lazy val statistics =
     Statistics(sizeInBytes = output.map(_.dataType.defaultSize).sum * data.length)
+
+  def toSQL(inlineTableName: String): String = {
+    require(data.nonEmpty)
+    val types = output.map(_.dataType)
+    val rows = data.map { row =>
+      val cells = row.toSeq(types).zip(types).map { case (v, tpe) => Literal(v, tpe).sql }
+      cells.mkString("(", ", ", ")")
+    }
+    "VALUES " + rows.mkString(", ") +
+      " AS " + inlineTableName +
+      output.map(_.name).mkString("(", ", ", ")")
+  }
 }

sql/core/src/main/scala/org/apache/spark/sql/catalyst/SQLBuilder.scala

@@ -205,6 +205,9 @@ class SQLBuilder private (
     case p: ScriptTransformation =>
       scriptTransformationToSQL(p)
 
+    case p: LocalRelation =>
+      p.toSQL(newSubqueryName())
+
     case OneRowRelation =>
       ""
 

sql/hive/src/test/resources/sqlgen/inline_tables.sql

+-- This file is automatically generated by LogicalPlanToSQLSuite.
+select * from values ("one", 1), ("two", 2), ("three", null) as data(a, b) where b > 1
+--------------------------------------------------------------------------------
+SELECT `gen_attr_0` AS `a`, `gen_attr_1` AS `b` FROM (SELECT `gen_attr_0`, `gen_attr_1` FROM (VALUES ("one", 1), ("two", 2), ("three", CAST(NULL AS INT)) AS gen_subquery_0(gen_attr_0, gen_attr_1)) AS data WHERE (`gen_attr_1` > 1)) AS data

sql/hive/src/test/scala/org/apache/spark/sql/catalyst/LogicalPlanToSQLSuite.scala

@@ -1102,4 +1102,12 @@ class LogicalPlanToSQLSuite extends SQLBuilderTest with SQLTestUtils {
       checkSQL("select * from orc_t", "select_orc_table")
     }
   }
+
+  test("inline tables") {
+    checkSQL(
+      """
+        |select * from values ("one", 1), ("two", 2), ("three", null) as data(a, b) where b > 1
+      """.stripMargin,
+      "inline_tables")
+  }
 }