Adding CommentsΒΆ

Let us understand how to create table with comments in Hive using orders as example.

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.

val username = System.getProperty("user.name")

import org.apache.spark.sql.SparkSession

val username = System.getProperty("user.name")
val spark = SparkSession.
    builder.
    config("spark.ui.port", "0").
    config("spark.sql.warehouse.dir", s"/user/${username}/warehouse").
    enableHiveSupport.
    appName(s"${username} | Spark SQL - Managing Tables - Basic DDL and DML").
    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

  • We can specify comments for both columns as well as tables using COMMENT keyword.

%%sql

USE itversity_retail

%%sql

DROP TABLE IF EXISTS orders

%%sql

CREATE TABLE orders (
  order_id INT COMMENT 'Unique order id',
  order_date STRING COMMENT 'Date on which order is placed',
  order_customer_id INT COMMENT 'Customer id who placed the order',
  order_status STRING COMMENT 'Current status of the order'
) COMMENT 'Table to save order level details'

  • Using Spark SQL with Python or Scala

spark.sql("USE itversity_retail")

spark.sql("DROP TABLE orders")

spark.sql("""
CREATE TABLE orders (
  order_id STRING COMMENT 'Unique order id',
  order_date STRING COMMENT 'Date on which order is placed',
  order_customer_id INT COMMENT 'Customer id who placed the order',
  order_status STRING COMMENT 'Current status of the order'
) COMMENT 'Table to save order level details'
""")

  • Default field delimiter is \001 character.

  • We can see the comments using DESCRIBE orders or DESCRIBE FORMATTED orders.

%%sql

DESCRIBE orders

%%sql

DESCRIBE FORMATTED orders

spark.sql("DESCRIBE FORMATTED orders").show(200, false) // Scala
Overview of Data Types Loading Data into Tables - Local