How to implement auto increment in spark SQL(PySpa

问题:

I need to implement a auto increment column in my spark sql table, how could i do that. Kindly guide me. i am using pyspark 2.0

Thank you Kalyan

回答1:

I would write/reuse stateful Hive udf and register with pySpark as Spark SQL does have good support for Hive.

check this line @UDFType(deterministic = false, stateful = true) in below code to make sure it's stateful UDF.

package org.apache.hadoop.hive.contrib.udf;

import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.hive.ql.udf.UDFType;
import org.apache.hadoop.io.LongWritable;

/**
 * UDFRowSequence.
 */
@Description(name = "row_sequence",
    value = "_FUNC_() - Returns a generated row sequence number starting from 1")
@UDFType(deterministic = false, stateful = true)
public class UDFRowSequence extends UDF
{
  private LongWritable result = new LongWritable();

  public UDFRowSequence() {
    result.set(0);
  }

  public LongWritable evaluate() {
    result.set(result.get() + 1);
    return result;
  }
}

// End UDFRowSequence.java

Now build the jar and add the location when pyspark get's started.

$ pyspark --jars your_jar_name.jar

Then register with sqlContext.

sqlContext.sql("CREATE TEMPORARY FUNCTION row_seq AS 'org.apache.hadoop.hive.contrib.udf.UDFRowSequence'")

Now use row_seq() in select query

sqlContext.sql("SELECT row_seq(), col1, col2 FROM table_name")

Project to use Hive UDFs in pySpark