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From Spark 2.0, you can easily read data from Hive data warehouse and also write/append new data to Hive tables.

This page shows how to operate with Hive in Spark including:

  • Create DataFrame from existing Hive table
  • Save DataFrame to a new Hive table
  • Append data to the existing Hive table via both INSERT statement and append write mode.

Python is used as programming language. The syntax for Scala will be very similar.

Create a SparkSession with Hive supported

Run the following code to create a Spark session with Hive support:

from pyspark.sql import SparkSession

appName = "PySpark Hive Example"

master = "local"

# Create Spark session with Hive supported.

spark = SparkSession.builder \

.appName(appName) \

.master(master) \

.enableHiveSupport() \

.getOrCreate()

Read data from Hive

And now we can use the SparkSession object to read data from Hive database:

# Read data from Hive database test_db, table name: test_table.

df = spark.sql("select * from test_db.test_table")

df.show()

I use Derby as Hive metastore and I already created on database named test_db with a table named test_table. Inside the table, there are two records.

The results look similar to the following:

+---+-----+
| id|value|
+---+-----+
|  1|  ABC|
|  2|  DEF|
+---+-----+

Add a new column

# Let's add a new column

df = df.withColumn("NewColumn",lit('Test'))

df.show()

The following is the result:

+---+-----+---------+
| id|value|NewColumn|
+---+-----+---------+
|  1|  ABC|     Test|
|  2|  DEF|     Test|
+---+-----+---------+

Save DataFrame as a new Hive table

Use the following code to save the data frame to a new hive table named test_table2:

# Save df to a new table in Hive

df.write.mode("overwrite").saveAsTable("test_db.test_table2")

# Show the results using SELECT

spark.sql("select * from test_db.test_table2").show()

In the logs, I can see the new table is saved as Parquet by default:

Initialized Parquet WriteSupport with Catalyst schema:
{
   "type" : "struct",
   "fields" : [ {
     "name" : "id",
     "type" : "long",
     "nullable" : true,
     "metadata" : { }
   }, {
     "name" : "value",
     "type" : "string",
     "nullable" : true,
     "metadata" : {
       "HIVE_TYPE_STRING" : "varchar(100)"
     }
   }, {
     "name" : "NewColumn",
     "type" : "string",
     "nullable" : false,
     "metadata" : { }
   } ]
}
and corresponding Parquet message type:
message spark_schema {
   optional int64 id;
   optional binary value (UTF8);
   required binary NewColumn (UTF8);
}

Append data to existing Hive table

You can also append data to existing Hive table either via ‘INSERT SQL statement’ or ‘append’ write mode.

# Append data via SQL

spark.sql("insert into test_db.test_table2 values (3, 'GHI', 'SQL INSERT')")

spark.sql("select * from test_db.test_table2").show()

# Append data via code

df = spark.sql("select 4 as id, 'JKL' as value, 'Spark Write Append Mode' as NewColumn")

df.show()

df.write.mode("append").saveAsTable("test_db.test_table2")

spark.sql("select * from test_db.test_table2").show()

Both records are inserted into the table successfully as the following output shows:

+---+-----+--------------------+
| id|value|           NewColumn|
+---+-----+--------------------+
|  4|  JKL|Spark Write Appen...|
|  1|  ABC|                Test|
|  2|  DEF|                Test|
|  3|  GHI|          SQL INSERT|
+---+-----+--------------------+

Complete code - hive-example.py

from pyspark.sql import SparkSession
from pyspark.sql.functions import lit

appName = "PySpark Hive Example"
master = "local"

# Create Spark session with Hive supported.
spark = SparkSession.builder \
    .appName(appName) \
    .master(master) \
    .enableHiveSupport() \
    .getOrCreate()

# Read data from Hive database test_db, table name: test_table.
df = spark.sql("select * from test_db.test_table")
df.show()

# Let's add a new column
df = df.withColumn("NewColumn",lit('Test'))
df.show()

# Save df to a new table in Hive
df.write.mode("overwrite").saveAsTable("test_db.test_table2")
# Show the results using SELECT
spark.sql("select * from test_db.test_table2").show()

# Append data via SQL
spark.sql("insert into test_db.test_table2 values (3, 'GHI', 'SQL INSERT')")
spark.sql("select * from test_db.test_table2").show()

# Append data via code
df = spark.sql("select 4 as id, 'JKL' as value, 'Spark Write Append Mode' as NewColumn")
df.show()
df.write.mode("append").saveAsTable("test_db.test_table2")
spark.sql("select * from test_db.test_table2").show()

Have fun with Spark!

info Last modified by Raymond at 9 months ago

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