Pre-defined Functions¶

We typically process data in the columns using functions in pyspark.sql.functions. Let us understand details about these functions in detail as part of this module.

Let us recap about Functions or APIs to process Data Frames.
Projection - select or withColumn or drop or selectExpr
Filtering - filter or where
Grouping data by key and perform aggregations - groupBy
Sorting data - sort or orderBy
We can pass column names or literals or expressions to all the Data Frame APIs.
Expressions include arithmetic operations, transformations using functions from pyspark.sql.functions.
There are approximately 300 functions under pyspark.sql.functions.
We will talk about some of the important functions used for String Manipulation, Date Manipulation etc.

Let us start spark context for this Notebook so that we can execute the code provided. You can sign up for our 10 node state of the art cluster/labs to learn Spark SQL using our unique integrated LMS.

from pyspark.sql import SparkSession

import getpass
username = getpass.getuser()

spark = SparkSession. \
    builder. \
    config('spark.ui.port', '0'). \
    config("spark.sql.warehouse.dir", f"/user/{username}/warehouse"). \
    enableHiveSupport(). \
    appName(f'{username} | Python - Processing Column Data'). \
    master('yarn'). \
    getOrCreate()

If you are going to use CLIs, you can use Spark SQL using one of the 3 approaches.

Using Spark SQL

spark2-sql \
    --master yarn \
    --conf spark.ui.port=0 \
    --conf spark.sql.warehouse.dir=/user/${USER}/warehouse

Using Scala

spark2-shell \
    --master yarn \
    --conf spark.ui.port=0 \
    --conf spark.sql.warehouse.dir=/user/${USER}/warehouse

Using Pyspark

pyspark2 \
    --master yarn \
    --conf spark.ui.port=0 \
    --conf spark.sql.warehouse.dir=/user/${USER}/warehouse

Here are some of the examples of using functions to take care of required transformations.

# Reading data

orders = spark.read.csv(
    '/public/retail_db/orders',
    schema='order_id INT, order_date STRING, order_customer_id INT, order_status STRING'
)

# Importing functions

from pyspark.sql.functions import date_format

orders.show()

+--------+--------------------+-----------------+---------------+
|order_id|          order_date|order_customer_id|   order_status|
+--------+--------------------+-----------------+---------------+
|       1|2013-07-25 00:00:...|            11599|         CLOSED|
|       2|2013-07-25 00:00:...|              256|PENDING_PAYMENT|
|       3|2013-07-25 00:00:...|            12111|       COMPLETE|
|       4|2013-07-25 00:00:...|             8827|         CLOSED|
|       5|2013-07-25 00:00:...|            11318|       COMPLETE|
|       6|2013-07-25 00:00:...|             7130|       COMPLETE|
|       7|2013-07-25 00:00:...|             4530|       COMPLETE|
|       8|2013-07-25 00:00:...|             2911|     PROCESSING|
|       9|2013-07-25 00:00:...|             5657|PENDING_PAYMENT|
|      10|2013-07-25 00:00:...|             5648|PENDING_PAYMENT|
|      11|2013-07-25 00:00:...|              918| PAYMENT_REVIEW|
|      12|2013-07-25 00:00:...|             1837|         CLOSED|
|      13|2013-07-25 00:00:...|             9149|PENDING_PAYMENT|
|      14|2013-07-25 00:00:...|             9842|     PROCESSING|
|      15|2013-07-25 00:00:...|             2568|       COMPLETE|
|      16|2013-07-25 00:00:...|             7276|PENDING_PAYMENT|
|      17|2013-07-25 00:00:...|             2667|       COMPLETE|
|      18|2013-07-25 00:00:...|             1205|         CLOSED|
|      19|2013-07-25 00:00:...|             9488|PENDING_PAYMENT|
|      20|2013-07-25 00:00:...|             9198|     PROCESSING|
+--------+--------------------+-----------------+---------------+
only showing top 20 rows

orders.printSchema()

root
 |-- order_id: integer (nullable = true)
 |-- order_date: string (nullable = true)
 |-- order_customer_id: integer (nullable = true)
 |-- order_status: string (nullable = true)

# Function as part of projections

orders.select('*', date_format('order_date', 'yyyyMM').alias('order_month')).show()

+--------+--------------------+-----------------+---------------+-----------+
|order_id|          order_date|order_customer_id|   order_status|order_month|
+--------+--------------------+-----------------+---------------+-----------+
|       1|2013-07-25 00:00:...|            11599|         CLOSED|     201307|
|       2|2013-07-25 00:00:...|              256|PENDING_PAYMENT|     201307|
|       3|2013-07-25 00:00:...|            12111|       COMPLETE|     201307|
|       4|2013-07-25 00:00:...|             8827|         CLOSED|     201307|
|       5|2013-07-25 00:00:...|            11318|       COMPLETE|     201307|
|       6|2013-07-25 00:00:...|             7130|       COMPLETE|     201307|
|       7|2013-07-25 00:00:...|             4530|       COMPLETE|     201307|
|       8|2013-07-25 00:00:...|             2911|     PROCESSING|     201307|
|       9|2013-07-25 00:00:...|             5657|PENDING_PAYMENT|     201307|
|      10|2013-07-25 00:00:...|             5648|PENDING_PAYMENT|     201307|
|      11|2013-07-25 00:00:...|              918| PAYMENT_REVIEW|     201307|
|      12|2013-07-25 00:00:...|             1837|         CLOSED|     201307|
|      13|2013-07-25 00:00:...|             9149|PENDING_PAYMENT|     201307|
|      14|2013-07-25 00:00:...|             9842|     PROCESSING|     201307|
|      15|2013-07-25 00:00:...|             2568|       COMPLETE|     201307|
|      16|2013-07-25 00:00:...|             7276|PENDING_PAYMENT|     201307|
|      17|2013-07-25 00:00:...|             2667|       COMPLETE|     201307|
|      18|2013-07-25 00:00:...|             1205|         CLOSED|     201307|
|      19|2013-07-25 00:00:...|             9488|PENDING_PAYMENT|     201307|
|      20|2013-07-25 00:00:...|             9198|     PROCESSING|     201307|
+--------+--------------------+-----------------+---------------+-----------+
only showing top 20 rows

orders.withColumn('order_month', date_format('order_date', 'yyyyMM')).show()

+--------+--------------------+-----------------+---------------+-----------+
|order_id|          order_date|order_customer_id|   order_status|order_month|
+--------+--------------------+-----------------+---------------+-----------+
|       1|2013-07-25 00:00:...|            11599|         CLOSED|     201307|
|       2|2013-07-25 00:00:...|              256|PENDING_PAYMENT|     201307|
|       3|2013-07-25 00:00:...|            12111|       COMPLETE|     201307|
|       4|2013-07-25 00:00:...|             8827|         CLOSED|     201307|
|       5|2013-07-25 00:00:...|            11318|       COMPLETE|     201307|
|       6|2013-07-25 00:00:...|             7130|       COMPLETE|     201307|
|       7|2013-07-25 00:00:...|             4530|       COMPLETE|     201307|
|       8|2013-07-25 00:00:...|             2911|     PROCESSING|     201307|
|       9|2013-07-25 00:00:...|             5657|PENDING_PAYMENT|     201307|
|      10|2013-07-25 00:00:...|             5648|PENDING_PAYMENT|     201307|
|      11|2013-07-25 00:00:...|              918| PAYMENT_REVIEW|     201307|
|      12|2013-07-25 00:00:...|             1837|         CLOSED|     201307|
|      13|2013-07-25 00:00:...|             9149|PENDING_PAYMENT|     201307|
|      14|2013-07-25 00:00:...|             9842|     PROCESSING|     201307|
|      15|2013-07-25 00:00:...|             2568|       COMPLETE|     201307|
|      16|2013-07-25 00:00:...|             7276|PENDING_PAYMENT|     201307|
|      17|2013-07-25 00:00:...|             2667|       COMPLETE|     201307|
|      18|2013-07-25 00:00:...|             1205|         CLOSED|     201307|
|      19|2013-07-25 00:00:...|             9488|PENDING_PAYMENT|     201307|
|      20|2013-07-25 00:00:...|             9198|     PROCESSING|     201307|
+--------+--------------------+-----------------+---------------+-----------+
only showing top 20 rows

# Function as part of where or filter

orders. \
    filter(date_format('order_date', 'yyyyMM') == 201401). \
    show()

+--------+--------------------+-----------------+---------------+
|order_id|          order_date|order_customer_id|   order_status|
+--------+--------------------+-----------------+---------------+
|   25876|2014-01-01 00:00:...|             3414|PENDING_PAYMENT|
|   25877|2014-01-01 00:00:...|             5549|PENDING_PAYMENT|
|   25878|2014-01-01 00:00:...|             9084|        PENDING|
|   25879|2014-01-01 00:00:...|             5118|        PENDING|
|   25880|2014-01-01 00:00:...|            10146|       CANCELED|
|   25881|2014-01-01 00:00:...|             3205|PENDING_PAYMENT|
|   25882|2014-01-01 00:00:...|             4598|       COMPLETE|
|   25883|2014-01-01 00:00:...|            11764|        PENDING|
|   25884|2014-01-01 00:00:...|             7904|PENDING_PAYMENT|
|   25885|2014-01-01 00:00:...|             7253|        PENDING|
|   25886|2014-01-01 00:00:...|             8195|     PROCESSING|
|   25887|2014-01-01 00:00:...|            10062|        PENDING|
|   25888|2014-01-01 00:00:...|             6735|       COMPLETE|
|   25889|2014-01-01 00:00:...|            10045|       COMPLETE|
|   25890|2014-01-01 00:00:...|             2581|        PENDING|
|   25891|2014-01-01 00:00:...|             3037|         CLOSED|
|   25892|2014-01-01 00:00:...|             3853|        ON_HOLD|
|   25893|2014-01-01 00:00:...|             8679|PENDING_PAYMENT|
|   25894|2014-01-01 00:00:...|             7839|     PROCESSING|
|   25895|2014-01-01 00:00:...|             1044|       COMPLETE|
+--------+--------------------+-----------------+---------------+
only showing top 20 rows

# Function as part of groupBy

orders. \
    groupBy(date_format('order_date', 'yyyyMM').alias('order_month')). \
    count(). \
    show()

+-----------+-----+
|order_month|count|
+-----------+-----+
|     201401| 5908|
|     201405| 5467|
|     201312| 5892|
|     201310| 5335|
|     201311| 6381|
|     201307| 1533|
|     201407| 4468|
|     201403| 5778|
|     201404| 5657|
|     201402| 5635|
|     201309| 5841|
|     201406| 5308|
|     201308| 5680|
+-----------+-----+

Mastering Pyspark

Pre-defined Functions¶