How do I get the Hive table schema in Spark?
Spark SQL – Hive Tables
- Start Spark Shell. First, we have to start the Spark Shell.
- Create SQLContext object.
- Create table using HiveQL.
- Load data into table using HiveQL.
- Select fields from the table.
Table of Contents
How do I get Hive data from Spark?
Chapter 9. Accessing Hive Tables from Spark
- Start the Spark Shell on a YARN cluster: su hdfs ./bin/spark-shell –num-executors 2 –executor-memory 512m –master yarn-client.
- Create hive context: scala> val hiveContext = new org.apache.spark.sql.hive.HiveContext(sc)
How do I return an empty dataframe in spark?
Approach 1: Using the createDataFrame function
- import apache organization Spark – spark. sql. types
- import apache organization Spark – spark. sql. _
- value schema = StructType(
- StructField(“empno”, StringType, true) ::
- StructField(“ename”, StringType, true) ::
- StructField(“designation”, StringType, true) ::
- StructField(“admin”, StringType, true) :: Nil.
- )
How is data stored from Spark to Hive Table?
Spark: save dataframe to hive table
- Create a DataFrame from an existing Hive table.
- Save the DataFrame to a new Hive table.
- Add data to the existing Hive table via the INSERT statement and attached write mode.
How does Hive work on Spark?
Spark SQL also supports reading and writing data stored in Apache Hive. However, since Hive has a large number of dependencies, these dependencies are not included in the default Spark distribution. If hive dependencies can be found on the classpath, Spark will load them automatically.
How do I pass an empty data frame?
Import python pandas module like this,
- import pandas as pd.
- # Create an empty data frame with only column names.
- Columns: [User_ID, UserName, Action]
- def __init__(self, data=None, index=None, columns=None, dtype=None,
- # Add rows to the empty data frame by adding dictionaries.
- User_ID Username Action.
How to create hive table from Spark dataframe?
The first is to create a direct hive table via the dataframe. The second is to take the schema of this dataframe and create a table in Hive.
How to create a Hive database in Scala?
To connect to Hive from Scala, you need to start hiveserver2 from $HIVE_HOME/bin Here is a complete Scala example of how to create a Hive database. Note: If you are using an older version of Hive, you must use the org.apache.hadoop.hive.jdbc.HiveDriver driver and your connection string must start with jdbc:hive://
Is it possible to create a table in HiveQL?
With HiveContext, you can create and look up tables in the HiveMetaStore and write queries against them with HiveQL. Users who don’t have an existing Hive implementation can still create a HiveContext.
One of the most important pieces of Spark SQL’s Hive support is the interaction with the Hive metastore, which allows Spark SQL to access metadata from Hive tables. As of Spark 1.4.0, a single Spark SQL binary build can be used to query different versions of Hive metastores, using the configuration described below.