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Hive Metastore Administration

Introduction

All the metadata for Hive tables and partitions are accessed through the Hive Metastore. Metadata is persisted using JPOX ORM solution (Data Nucleus) so any database that is supported by it can be used by Hive. Most of the commercial relational databases and many open source databases are supported. See the list of supported databases in section below.

You can find an E/R diagram for the metastore here.

There are 2 different ways to setup the metastore server and metastore database using different Hive configurations:

Configuration options for metastore database where metadata is persisted:

Configuration options for metastore server:

Basic Configuration Parameters

The relevant configuration parameters are shown here. (Non-metastore parameters are described in Configuring Hive. Also see the Language Manual's Hive Configuration Properties, including Metastore and Hive Metastore Security.)

Also see hivemetastore-site.xml documentation under Configuring Hive.

Configuration Parameter

Description

javax.jdo.option.ConnectionURL

JDBC connection string for the data store which contains metadata

javax.jdo.option.ConnectionDriverName

JDBC Driver class name for the data store which contains metadata

hive.metastore.uris

Hive connects to one of these URIs to make metadata requests to a remote Metastore (comma separated list of URIs)

hive.metastore.local

local or remote metastore (removed as of Hive 0.10: If hive.metastore.uris is empty local mode is assumed, remote otherwise)

hive.metastore.warehouse.dir

URI of the default location for native tables

The Hive metastore is stateless and thus there can be multiple instances to achieve High Availability. Using hive.metastore.uris it is possible to specify multiple remote metastores. Hive will use the first one from the list by default but will pick a random one on connection failure and will try to reconnect.

Additional Configuration Parameters

These metastore configuration parameters were carried over from old documentation without a guarantee that they all still exist (see the HiveConf java class for current Hive configuration options):

Configuration Parameter

Description

Default Value

hive.metastore.metadb.dir

The location of filestore metadata base directory. (Functionality removed in 0.4.0 with HIVE-143.)

 

hive.metastore.rawstore.impl

Name of the class that implements the org.apache.hadoop.hive.metastore.rawstore interface. This class is used to store and retrieval of raw metadata objects such as table, database. (Hive 0.8.1 and later.)

 

org.jpox.autoCreateSchema

Creates necessary schema on startup if one doesn't exist. (The schema includes tables, columns, and so on.) Set to false after creating it once.

 

org.jpox.fixedDatastore

Whether the datastore schema is fixed.

 

datanucleus.autoStartMechanism

Whether to initialize on startup.

 

hive.metastore.ds.connection.url.hook

Name of the hook to use for retriving the JDO connection URL. If empty, the value in javax.jdo.option.ConnectionURL is used as the connection URL. (Hive 0.6 and later.)

 

hive.metastore.ds.retry.attempts

The number of times to retry a call to the backing datastore if there were a connection error.
(Hive 0.6 through 0.12; removed in 0.13.0 – use hive.hmshandler.retry.attempts instead.)

1

hive.metastore.ds.retry.interval

The number of miliseconds between datastore retry attempts.
(Hive 0.6 through 0.12; removed in 0.13.0 – use hive.hmshandler.retry.interval instead.)

1000

hive.metastore.server.min.threads

Minimum number of worker threads in the Thrift server's pool.
(Hive 0.6 and later.)

200

hive.metastore.server.max.threads

Maximum number of worker threads in the Thrift server's pool.
(Hive 0.6 and later.)

100000 since Hive 0.8.1

hive.metastore.filter.hook

Metastore hook class for further filtering the metadata read results on client side.
(Hive 0.15 and later.)

org.apache.hadoop.hive.metastore.DefaultMetaStoreFilterHookImpl

hive.metastore.port

Hive metastore listener port.
(Hive 1.3.0 and later.)

9083

Data Nucleus Auto Start

Configuring datanucleus.autoStartMechanism is highly recommended

Configuring auto start for data nucleus is highly recommended. See HIVE-4762 for more details.

Default Configuration

The default configuration sets up an embedded metastore which is used in unit tests and is described in the next section. More practical options are described in the subsequent sections.

Local/Embedded Metastore Database (Derby)

An embedded metastore database is mainly used for unit tests. Only one process can connect to the metastore database at a time, so it is not really a practical solution but works well for unit tests.

For unit tests Local/Embedded Metastore Server configuration for the metastore server is used in conjunction with embedded database.

Derby is the default database for the embedded metastore.

Config Param

Config Value

Comment

javax.jdo.option.ConnectionURL

jdbc:derby:;databaseName=
../build/test/junit_metastore_db;create=true

Derby database located at hive/trunk/build...

javax.jdo.option.ConnectionDriverName

org.apache.derby.jdbc.EmbeddedDriver

Derby embeded JDBC driver class.

hive.metastore.warehouse.dir

file://${user.dir}/../build/ql/test/data/warehouse

Unit test data goes in here on your local filesystem.

If you want to run Derby as a network server so the metastore can be accessed from multiple nodes, see Hive Using Derby in Server Mode.

Remote Metastore Database

In this configuration, you would use a traditional standalone RDBMS server. The following example configuration will set up a metastore in a MySQL server. This configuration of metastore database is recommended for any real use.

Config Param

Config Value

Comment

javax.jdo.option.ConnectionURL

jdbc:mysql://<host name>/<database name>?createDatabaseIfNotExist=true

metadata is stored in a MySQL server

javax.jdo.option.ConnectionDriverName

com.mysql.jdbc.Driver

MySQL JDBC driver class

javax.jdo.option.ConnectionUserName

<user name>

user name for connecting to MySQL server

javax.jdo.option.ConnectionPassword

<password>

password for connecting to MySQL server

Local/Embedded Metastore Server

In local/embedded metastore setup, the metastore server component is used like a library within the Hive Client. Each Hive Client will open a connection to the database and make SQL queries against it. Make sure that the database is accessible from the machines where Hive queries are executed since this is a local store. Also make sure the JDBC client library is in the classpath of Hive Client. This configuration is often used with HiveServer2 (to use embedded metastore only with HiveServer2 add "-hiveconf hive.metastore.uris=' '" in command line parameters of the hiveserver2 start command or use hiveserver2-site.xml (available in Hive 0.14)).

Config Param

Config Value

Comment

hive.metastore.uris

not needed because this is local store

 

hive.metastore.local

true

this is local store (removed in Hive 0.10, see configuration description section)

hive.metastore.warehouse.dir

<base hdfs path>

default location for Hive tables

Remote Metastore Server

In remote metastore setup, all Hive Clients will make a connection to a metastore server which in turn queries the datastore (MySQL in this example) for metadata. Metastore server and client communicate using Thrift Protocol. Starting with Hive 0.5.0, you can start a Thrift server by executing the following command:

hive --service metastore

In versions of Hive earlier than 0.5.0, it's instead necessary to run the Thrift server via direct execution of Java:

$JAVA_HOME/bin/java  -Xmx1024m -Dlog4j.configuration=file://$HIVE_HOME/conf/hms-log4j.properties -Djava.library.path=$HADOOP_HOME/lib/native/Linux-amd64-64/ -cp $CLASSPATH org.apache.hadoop.hive.metastore.HiveMetaStore

If you execute Java directly, then JAVA_HOME, HIVE_HOME, HADOOP_HOME must be correctly set; CLASSPATH should contain Hadoop, Hive (lib and auxlib), and Java jars.

Server Configuration Parameters

The following example uses a Remote Metastore Database.

Config Param

Config Value

Comment

javax.jdo.option.ConnectionURL

jdbc:mysql://<host name>/<database name>?createDatabaseIfNotExist=true

metadata is stored in a MySQL server

javax.jdo.option.ConnectionDriverName

com.mysql.jdbc.Driver

MySQL JDBC driver class

javax.jdo.option.ConnectionUserName

<user name>

user name for connecting to MySQL server

javax.jdo.option.ConnectionPassword

<password>

password for connecting to MySQL server

hive.metastore.warehouse.dir

<base hdfs path>

default location for Hive tables.

Client Configuration Parameters

Config Param

Config Value

Comment

hive.metastore.uris

thrift://<host_name>:<port>

host and port for the Thrift metastore server

hive.metastore.local

false

This is local store.  Note: This is no longer needed as of Hive 0.10.  Setting hive.metastore.uris is sufficient.

hive.metastore.warehouse.dir

<base hdfs path>

default location for Hive tables.

If you are using MySQL as the datastore for metadata, put MySQL jdbc libraries in HIVE_HOME/lib before starting Hive Client or HiveMetastore Server.

To change the metastore port, use this hive command:

hive --service metastore -p <port_num>

Supported Backend Databases for Metastore

DatabaseMinimum Supported VersionName for Parameter Values
MySQL5.6.17mysql
Postgres9.1.13
postgres
Oracle11goracle
MS SQL Server2008 R2mssql

Metastore Schema Consistency and Upgrades

Version

Introduced in Hive 0.12.0. See HIVE-3764.

Hive now records the schema version in the metastore database and verifies that the metastore schema version is compatible with Hive binaries that are going to accesss the metastore. Note that the Hive properties to implicitly create or alter the existing schema are disabled by default. Hive will not attempt to change the metastore schema implicitly. When you execute a Hive query against an old schema, it will fail to access the metastore.

To suppress the schema check and allow the metastore to implicitly modify the schema, you need to set a configuration property hive.metastore.schema.verification to false in hive-site.xml.

Starting in release 0.12, Hive also includes an off-line schema tool to initialize and upgrade the metastore schema. Please refer to the details here.

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