[SPARK-22014] Sample windows in Spark SQL

• Type: Wish
• Status: Closed
• Priority: Minor
• Resolution: Auto Closed
• Affects Version/s: 2.2.0
• Component/s: DStreams, SQL
• Assignee: Unassigned
• Reporter: Simon Schiff
• Created: 14/Sep/17 13:58
• Updated: 15/Apr/18 19:18
• Resolved: 15/Apr/18 19:17

Description

Hello,
I am using spark to process measurement data. It is possible to create sample windows in Spark Streaming, where the duration of the window is smaller than the slide. But when I try to do the same with Spark SQL (The measurement data has a time stamp column) then I got an analysis exception:

Exception in thread "main" org.apache.spark.sql.AnalysisException: cannot resolve 'timewindow(timestamp, 60000000, 180000000, 0)' due to data type mismatch: The slide duration (180000000) must be less than or equal to the windowDuration (60000000)

Here is a example:

import java.sql.Timestamp;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

import org.apache.spark.api.java.function.Function;
import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Encoders;
import org.apache.spark.sql.Row;
import org.apache.spark.sql.RowFactory;
import org.apache.spark.sql.SparkSession;
import org.apache.spark.sql.functions;
import org.apache.spark.sql.types.DataTypes;
import org.apache.spark.sql.types.StructField;
import org.apache.spark.sql.types.StructType;

public class App {
	public static Timestamp createTimestamp(String in) throws Exception {
		SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
	    Date parsedDate = dateFormat.parse(in);
	    return new Timestamp(parsedDate.getTime());
	}
	
	public static void main(String[] args) {
		SparkSession spark = SparkSession.builder().appName("Window Sampling Example").getOrCreate();
		
		List<String> sensorData = new ArrayList<String>();
		sensorData.add("2017-08-04 00:00:00, 22.75");
		sensorData.add("2017-08-04 00:01:00, 23.82");
		sensorData.add("2017-08-04 00:02:00, 24.15");
		sensorData.add("2017-08-04 00:03:00, 23.16");
		sensorData.add("2017-08-04 00:04:00, 22.62");
		sensorData.add("2017-08-04 00:05:00, 22.89");
		sensorData.add("2017-08-04 00:06:00, 23.21");
		sensorData.add("2017-08-04 00:07:00, 24.59");
		sensorData.add("2017-08-04 00:08:00, 24.44");
		
		Dataset<String> in = spark.createDataset(sensorData, Encoders.STRING());
		
		StructType sensorSchema = DataTypes.createStructType(new StructField[] { 
				DataTypes.createStructField("timestamp", DataTypes.TimestampType, false),
				DataTypes.createStructField("value", DataTypes.DoubleType, false),
		});
		
		Dataset<Row> data = spark.createDataFrame(in.toJavaRDD().map(new Function<String, Row>() {
			public Row call(String line) throws Exception {
				return RowFactory.create(createTimestamp(line.split(",")[0]), Double.parseDouble(line.split(",")[1]));
			}
		}), sensorSchema);
		
		data.groupBy(functions.window(data.col("timestamp"), "1 minutes", "3 minutes")).avg("value").orderBy("window").show(false);
	}
}

I think there should be no difference (duration and slide) in a "Spark Streaming window" and a "Spark SQL window" function.

Issue Links

• links to: [Github] Pull Request #19526 (SimonUzL)