Apache Spark

1. Supported Versions

Supported versions of Spark and Scala are as follows:

Spark Version	Scala Version
2.4.0-latest	2.11, 2.12

2. Precautions

1. The current version of spark-iotdb-connector supports Scala 2.11 and 2.12, but not 2.13.
2. spark-iotdb-connector supports usage in Spark for both Java, Scala, and PySpark.

3. Deployment

spark-iotdb-connector has two use cases: IDE development and spark-shell debugging.

3.1 IDE Development

For IDE development, simply add the following dependency to the pom.xml file:

    <dependency>
      <groupId>org.apache.iotdb</groupId>
      <!-- spark-iotdb-connector_2.11 or spark-iotdb-connector_2.13 -->
      <artifactId>spark-iotdb-connector_2.12.10</artifactId>
      <version>${iotdb.version}</version>
    </dependency>

3.2 spark-shell Debugging

To use spark-iotdb-connector in spark-shell, you need to download the with-dependencies version of the jar package
from the official website. After that, copy the jar package to the ${SPARK_HOME}/jars directory.
Simply execute the following command:

cp spark-iotdb-connector_2.12.10-${iotdb.version}.jar $SPARK_HOME/jars/

In addition, to ensure that spark can use JDBC and IoTDB connections, you need to do the following:

Run the following command to compile the IoTDB JDBC connector:

mvn clean package -pl iotdb-client/jdbc -am -DskipTests -P get-jar-with-dependencies

The compiled jar package is located in the following directory:

$IoTDB_HOME/iotdb-client/jdbc/target/iotdb-jdbc-{version}-SNAPSHOT-jar-with-dependencies.jar

At last, copy the jar package to the ${SPARK_HOME}/jars directory. Simply execute the following command:

cp iotdb-jdbc-{version}-SNAPSHOT-jar-with-dependencies.jar $SPARK_HOME/jars/

4. Usage

4.1Parameters

Parameter	Description	Default Value	Scope	Can be Empty
url	Specifies the JDBC URL of IoTDB	null	read, write	false
user	The username of IoTDB	root	read, write	true
password	The password of IoTDB	root	read, write	true
sql	Specifies the SQL statement for querying	null	read	true
numPartition	Specifies the partition number of the DataFrame when in read, and the write concurrency number when in write	1	read, write	true
lowerBound	The start timestamp of the query (inclusive)	0	read	true
upperBound	The end timestamp of the query (inclusive)	0	read	true

4.2 Reading Data from IoTDB

Here is an example that demonstrates how to read data from IoTDB into a DataFrame:

import org.apache.iotdb.spark.db._

val df = spark.read.format("org.apache.iotdb.spark.db")
  .option("user", "root")
  .option("password", "root")
  .option("url", "jdbc:iotdb://127.0.0.1:6667/")
  .option("sql", "select ** from root") // query SQL
  .option("lowerBound", "0") // lower timestamp bound
  .option("upperBound", "100000000") // upper timestamp bound
  .option("numPartition", "5") // number of partitions
  .load

df.printSchema()

df.show()

4.3 Writing Data to IoTDB

Here is an example that demonstrates how to write data to IoTDB:

// Construct narrow table data
val df = spark.createDataFrame(List(
  (1L, "root.test.d0", 1, 1L, 1.0F, 1.0D, true, "hello"),
  (2L, "root.test.d0", 2, 2L, 2.0F, 2.0D, false, "world")))

val dfWithColumn = df.withColumnRenamed("_1", "Time")
  .withColumnRenamed("_2", "Device")
  .withColumnRenamed("_3", "s0")
  .withColumnRenamed("_4", "s1")
  .withColumnRenamed("_5", "s2")
  .withColumnRenamed("_6", "s3")
  .withColumnRenamed("_7", "s4")
  .withColumnRenamed("_8", "s5")

// Write narrow table data
dfWithColumn
  .write
  .format("org.apache.iotdb.spark.db")
  .option("url", "jdbc:iotdb://127.0.0.1:6667/")
  .save

// Construct wide table data
val df = spark.createDataFrame(List(
  (1L, 1, 1L, 1.0F, 1.0D, true, "hello"),
  (2L, 2, 2L, 2.0F, 2.0D, false, "world")))

val dfWithColumn = df.withColumnRenamed("_1", "Time")
  .withColumnRenamed("_2", "root.test.d0.s0")
  .withColumnRenamed("_3", "root.test.d0.s1")
  .withColumnRenamed("_4", "root.test.d0.s2")
  .withColumnRenamed("_5", "root.test.d0.s3")
  .withColumnRenamed("_6", "root.test.d0.s4")
  .withColumnRenamed("_7", "root.test.d0.s5")

// Write wide table data
dfWithColumn.write.format("org.apache.iotdb.spark.db")
  .option("url", "jdbc:iotdb://127.0.0.1:6667/")
  .option("numPartition", "10")
  .save

4.4 Wide and Narrow Table Conversion

Here are examples of how to convert between wide and narrow tables:

• From wide to narrow

import org.apache.iotdb.spark.db._

val wide_df = spark.read.format("org.apache.iotdb.spark.db").option("url", "jdbc:iotdb://127.0.0.1:6667/").option("sql", "select * from root.** where time < 1100 and time > 1000").load
val narrow_df = Transformer.toNarrowForm(spark, wide_df)

• From narrow to wide

import org.apache.iotdb.spark.db._

val wide_df = Transformer.toWideForm(spark, narrow_df)

5. Wide and Narrow Tables

Using the TsFile structure as an example: there are three measurements in the TsFile pattern,
namely Status, Temperature, and Hardware. The basic information for each of these three measurements is as
follows:

Name	Type	Encoding
Status	Boolean	PLAIN
Temperature	Float	RLE
Hardware	Text	PLAIN

The existing data in the TsFile is as follows:

• d1:root.ln.wf01.wt01
• d2:root.ln.wf02.wt02

time	d1.status	time	d1.temperature	time	d2.hardware	time	d2.status
1	True	1	2.2	2	"aaa"	1	True
3	True	2	2.2	4	"bbb"	2	False
5	False	3	2.1	6	"ccc"	4	True

The wide (default) table form is as follows:

Time	root.ln.wf02.wt02.temperature	root.ln.wf02.wt02.status	root.ln.wf02.wt02.hardware	root.ln.wf01.wt01.temperature	root.ln.wf01.wt01.status	root.ln.wf01.wt01.hardware
1	null	true	null	2.2	true	null
2	null	false	aaa	2.2	null	null
3	null	null	null	2.1	true	null
4	null	true	bbb	null	null	null
5	null	null	null	null	false	null
6	null	null	ccc	null	null	null

You can also use the narrow table format as shown below:

Time	Device	status	hardware	temperature
1	root.ln.wf02.wt01	true	null	2.2
1	root.ln.wf02.wt02	true	null	null
2	root.ln.wf02.wt01	null	null	2.2
2	root.ln.wf02.wt02	false	aaa	null
3	root.ln.wf02.wt01	true	null	2.1
4	root.ln.wf02.wt02	true	bbb	null
5	root.ln.wf02.wt01	false	null	null
6	root.ln.wf02.wt02	null	ccc	null