[SPARK-15375][SQL][STREAMING] Add ConsoleSink to structure streaming

## What changes were proposed in this pull request?

Add ConsoleSink to structure streaming, user could use it to display dataframes on the console (useful for debugging and demostrating), similar to the functionality of `DStream#print`, to use it:

```
    val query = result.write
      .format("console")
      .trigger(ProcessingTime("2 seconds"))
      .startStream()
```

## How was this patch tested?

local verified.

Not sure it is suitable to add into structure streaming, please review and help to comment, thanks a lot.

Author: jerryshao <sshao@hortonworks.com>

Closes #13162 from jerryshao/SPARK-15375.

sql/core/src/main/resources/META-INF/services/org.apache.spark.sql.sources.DataSourceRegister

@@ -3,3 +3,4 @@ org.apache.spark.sql.execution.datasources.jdbc.DefaultSource
 org.apache.spark.sql.execution.datasources.json.DefaultSource
 org.apache.spark.sql.execution.datasources.parquet.DefaultSource
 org.apache.spark.sql.execution.datasources.text.DefaultSource
+org.apache.spark.sql.execution.streaming.ConsoleSinkProvider

sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/console.scala

+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.execution.streaming
+
+import org.apache.spark.internal.Logging
+import org.apache.spark.sql.{DataFrame, SQLContext}
+import org.apache.spark.sql.sources.{DataSourceRegister, StreamSinkProvider}
+
+class ConsoleSink(options: Map[String, String]) extends Sink with Logging {
+  // Number of rows to display, by default 20 rows
+  private val numRowsToShow = options.get("numRows").map(_.toInt).getOrElse(20)
+
+  // Truncate the displayed data if it is too long, by default it is true
+  private val isTruncated = options.get("truncate").map(_.toBoolean).getOrElse(true)
+
+  // Track the batch id
+  private var lastBatchId = -1L
+
+  override def addBatch(batchId: Long, data: DataFrame): Unit = synchronized {
+    val batchIdStr = if (batchId <= lastBatchId) {
+      s"Rerun batch: $batchId"
+    } else {
+      lastBatchId = batchId
+      s"Batch: $batchId"
+    }
+
+    // scalastyle:off println
+    println("-------------------------------------------")
+    println(batchIdStr)
+    println("-------------------------------------------")
+    // scalastyle:off println
+    data.show(numRowsToShow, isTruncated)
+  }
+}
+
+class ConsoleSinkProvider extends StreamSinkProvider with DataSourceRegister {
+  def createSink(
+      sqlContext: SQLContext,
+      parameters: Map[String, String],
+      partitionColumns: Seq[String]): Sink = {
+    new ConsoleSink(parameters)
+  }
+
+  def shortName(): String = "console"
+}

sql/core/src/test/scala/org/apache/spark/sql/streaming/DataFrameReaderWriterSuite.scala

@@ -524,4 +524,19 @@ class DataFrameReaderWriterSuite extends StreamTest with SharedSQLContext with B
     val e = intercept[AnalysisException](w.csv("non_exist_path"))
     assert(e.getMessage == "csv() can only be called on non-continuous queries;")
   }
+
+  test("ConsoleSink can be correctly loaded") {
+    LastOptions.clear()
+    val df = spark.read
+      .format("org.apache.spark.sql.streaming.test")
+      .stream()
+
+    val cq = df.write
+      .format("console")
+      .option("checkpointLocation", newMetadataDir)
+      .trigger(ProcessingTime(2.seconds))
+      .startStream()
+
+    cq.awaitTermination(2000L)
+  }
 }