Hi I'm trying to find out where SparkSQL stores the table metadata in Spark? If it is not in the Hive metastore by default, then where is it stored?
Here is explanation from spark-2.2.0 documentation
When not configured by the hive-site.xml, the context automatically creates metastore_db in the current directory and creates a directory configured by spark.sql.warehouse.dir, which defaults to the directory spark-warehouse in the current directory that the Spark application is started. Note that the hive.metastore.warehouse.dir property in hive-site.xml is deprecated since Spark 2.0.0. Instead, use spark.sql.warehouse.dir to specify the default location of database in warehouse.
Here is the link:
https://spark.apache.org/docs/latest/sql-data-sources-hive-tables.html
Related
Authority says:
When not configured by the hive-site.xml, the context automatically creates metastore_db in the current directory and creates a directory configured by spark.sql.warehouse.dir, which defaults to the directory spark-warehouse in the current directory that the Spark application is started. Note that the hive.metastore.warehouse.dir property in hive-site.xml is deprecated since Spark 2.0.0. Instead, use spark.sql.warehouse.dir to specify the default location of database in warehouse. You may need to grant write privilege to the user who starts the Spark application.
I have checked it as well. One directory gets created in spark.sql.warehouse.dir that houses all the data and there is a metadata_db directory in the current directory that stores the metadata for the data in spark.sql.warehouse.dir
Also, metadata is needed to retain partition information while reading from hive store. How does one manage this in production then? Should the metadata not be stored at spark.sql.warehouse.dir only so that the user does not have to worry about its maintenance?
Where is table created when I use SQL syntax for create table in Spark 2.*?
CREATE TABLE ... AS
Does spark store it internally somewhere of there has to always be Impala or Hive support for Spark tables to work?
By default (when no connection specified e.g. in hive-site.xml). Spark will save it in the local metastore that is on Derby db.
And it should be stored in spark-warehouse directory in your Spark directory or whatever is defined in spark.sql.warehouse.dir prop.
I was aware of the fact that Hive Metastore is used to store metadata of the tables that we create in HIVE but why do spark required Metastore, what is the default relation between Metastore and Spark
Does metasore is being used by spark SQL, if so is this to store dataframes metadata?
Why does spark by defaults checks for metastore connectivity even though iam not using any sql libraries?
Here is explanation from spark-2.2.0 documentation
When not configured by the hive-site.xml, the context automatically creates metastore_db in the current directory and creates a directory configured by spark.sql.warehouse.dir, which defaults to the directory spark-warehouse in the current directory that the Spark application is started. Note that the hive.metastore.warehouse.dir property in hive-site.xml is deprecated since Spark 2.0.0. Instead, use spark.sql.warehouse.dir to specify the default location of database in warehouse.
Going back a few versions of Spark it used to be required to put the
hive-site.xml
in the $SPARK_HOME/conf directory. Is that still the case?
The motivation for this question: we are unable to see hive tables that are defined within the metastore instance for which we did copy the hive-site.xml to the conf dir.
I have verified that the hive-site.xml is still used. It is selected from the classpath of spark. This may be set up via
export SPARK_CLASSPATH=/path/to/conf/dir
I'm trying to write a unit test case that relies on DataFrame.saveAsTable() (since it is backed by a file system). I point the hive warehouse parameter to a local disk location:
sql.sql(s"SET hive.metastore.warehouse.dir=file:///home/myusername/hive/warehouse")
By default, Embedded Mode of metastore should be enabled, thus doesn't require an external database.
But HiveContext seems to be ignoring this configuration: since I still get this error when calling saveAsTable():
MetaException(message:file:/user/hive/warehouse/users is not a directory or unable to create one)
org.apache.hadoop.hive.ql.metadata.HiveException: MetaException(message:file:/user/hive/warehouse/users is not a directory or unable to create one)
at org.apache.hadoop.hive.ql.metadata.Hive.createTable(Hive.java:619)
at org.apache.spark.sql.hive.HiveMetastoreCatalog.createDataSourceTable(HiveMetastoreCatalog.scala:172)
at org.apache.spark.sql.hive.execution.CreateMetastoreDataSourceAsSelect.run(commands.scala:224)
at org.apache.spark.sql.execution.ExecutedCommand.sideEffectResult$lzycompute(commands.scala:54)
at org.apache.spark.sql.execution.ExecutedCommand.sideEffectResult(commands.scala:54)
at org.apache.spark.sql.execution.ExecutedCommand.execute(commands.scala:64)
at org.apache.spark.sql.SQLContext$QueryExecution.toRdd$lzycompute(SQLContext.scala:1099)
at org.apache.spark.sql.SQLContext$QueryExecution.toRdd(SQLContext.scala:1099)
at org.apache.spark.sql.DataFrame.saveAsTable(DataFrame.scala:1121)
at org.apache.spark.sql.DataFrame.saveAsTable(DataFrame.scala:1071)
at org.apache.spark.sql.DataFrame.saveAsTable(DataFrame.scala:1037)
This is quite annoying, why is it still happening and how to fix it?
According to http://spark.apache.org/docs/latest/sql-programming-guide.html#sql
Note that the hive.metastore.warehouse.dir property in hive-site.xml
is deprecated since Spark 2.0.0. Instead, use spark.sql.warehouse.dir
to specify the default location of database in warehouse.
tl;dr Set hive.metastore.warehouse.dir while creating a SQLContext (or SparkSession).
The location of the default database for the Hive metastore warehouse is /user/hive/warehouse by default. It used to be set using hive.metastore.warehouse.dir Hive-specific configuration property (in a Hadoop configuration).
It's been a while since you asked this question (it's Spark 2.3 days), but that part has not changed since - if you use sql method of SQLContext (or SparkSession these days), it's simply too late to change where Spark creates the metastore database. It is far too late as the underlying infrastructure has been set up already (so you can use the SQLContext). The warehouse location has to be set up before the HiveContext / SQLContext / SparkSession initialization.
You should set hive.metastore.warehouse.dir while creating SparkSession (or SQLContext before Spark SQL 2.0) using config and (very important) enable the Hive support using enableHiveSupport.
config(key: String, value: String): Builder Sets a config option. Options set using this method are automatically propagated to both SparkConf and SparkSession's own configuration.
enableHiveSupport(): Builder Enables Hive support, including connectivity to a persistent Hive metastore, support for Hive serdes, and Hive user-defined functions.
You could use hive-site.xml configuration file or spark.hadoop prefix, but I'm digressing (and it strongly depends on the current configuration).
Another option is to just create a new database and then USE new_DATATBASE and then create the table. The warehouse will be created under the folder you ran the sql-spark.
I faced exactly theI faced exactly the same issues. I was running spark-submit command in shell action via oozie.
Setting warehouse directory doesn't worked for me while creating sparksession
All you need to do is to pass the pass the hive-site.xml in spark-submit command using below property:
--files ${location_of_hive-site.xml}