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# Spark IoTDB Connecter

## version

The versions required for Spark and Java are as follow:

| Spark Version | Scala Version | Java Version | TsFile |
| ------------- | ------------- | ------------ |------------ |
| `2.4.3`        | `2.11`        | `1.8`        | `0.9.2`|


## install
mvn clean scala:compile compile install


# 1. maven dependency

```
    <dependency>
      <groupId>org.apache.iotdb</groupId>
      <artifactId>spark-iotdb-connector</artifactId>
      <version>0.9.2</version>
    </dependency>
```


# 2. spark-shell user guide

```
spark-shell --jars spark-iotdb-connector-0.9.2.jar,iotdb-jdbc-0.9.2-jar-with-dependencies.jar

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

val df = spark.read.format("org.apache.iotdb.spark.db").option("url","jdbc:iotdb://127.0.0.1:6667/").option("sql","select * from root").load

df.printSchema()

df.show()
```

### if you want to partition your rdd, you can do as following
```
spark-shell --jars spark-iotdb-connector-0.9.2.jar,iotdb-jdbc-0.9.2-jar-with-dependencies.jar

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

val df = spark.read.format("org.apache.iotdb.spark.db").option("url","jdbc:iotdb://127.0.0.1:6667/").option("sql","select * from root").
                        option("lowerBound", [lower bound of time that you want query(include)]).option("upperBound", [upper bound of time that you want query(include)]).
                        option("numPartition", [the partition number you want]).load

df.printSchema()

df.show()
```

# 3. Schema Inference

Take the following TsFile structure as an example: There are three Measurements in the TsFile schema: status, temperature, and hardware. The basic information of these three measurements is as follows:

<center>
<table style="text-align:center">
	<tr><th colspan="2">Name</th><th colspan="2">Type</th><th colspan="2">Encode</th></tr>
	<tr><td colspan="2">status</td><td colspan="2">Boolean</td><td colspan="2">PLAIN</td></tr>
	<tr><td colspan="2">temperature</td><td colspan="2">Float</td><td colspan="2">RLE</td></tr>
	<tr><td colspan="2">hardware</td><td colspan="2">Text</td><td colspan="2">PLAIN</td></tr>
</table>
</center>

The existing data in the TsFile is as follows:


<center>
<table style="text-align:center">
	<tr><th colspan="4">device:root.ln.wf01.wt01</th><th colspan="4">device:root.ln.wf02.wt02</th></tr>
	<tr><th colspan="2">status</th><th colspan="2">temperature</th><th colspan="2">hardware</th><th colspan="2">status</th></tr>
	<tr><th>time</th><th>value</th><th>time</th><th>value</th><th>time</th><th>value</th><th>time</th><th>value</th></tr>
	<tr><td>1</td><td>True</td><td>1</td><td>2.2</td><td>2</td><td>"aaa"</td><td>1</td><td>True</td></tr>
	<tr><td>3</td><td>True</td><td>2</td><td>2.2</td><td>4</td><td>"bbb"</td><td>2</td><td>False</td></tr>
	<tr><td>5</td><td> False </td><td>3</td><td>2.1</td><td>6</td><td>"ccc"</td><td>4</td><td>True</td></tr>
</table>
</center>
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 narrow table form which as follows: (You can see part 4 about how to use narrow form)

| time | device_name                   | 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                          |

# 4. Transform between wide and narrow table

## 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. Java user guide
```
import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Row;
import org.apache.spark.sql.SparkSession;
import org.apache.iotdb.spark.db.*

public class Example {

  public static void main(String[] args) {
    SparkSession spark = SparkSession
        .builder()
        .appName("Build a DataFrame from Scratch")
        .master("local[*]")
        .getOrCreate();

    Dataset<Row> df = spark.read().format("org.apache.iotdb.spark.db")
        .option("url","jdbc:iotdb://127.0.0.1:6667/")
        .option("sql","select * from root").load();

    df.printSchema();

    df.show();
    
    Dataset<Row> narrowTable = Transformer.toNarrowForm(spark, df)
    narrowTable.show()
  }
}
```