8.2. Hive Connector

The Hive connector allows querying data stored in a Hive data warehouse. Hive is a combination of three components:

Data files in varying formats that are typically stored in the Hadoop Distributed File System (HDFS) or in Amazon S3.
Metadata about how the data files are mapped to schemas and tables. This metadata is stored in a database such as MySQL and is accessed via the Hive metastore service.
A query language called HiveQL. This query language is executed on a distributed computing framework such as MapReduce or Tez.

Presto only uses the first two components: the data and the metadata. It does not use HiveQL or any part of Hive’s execution environment.

Supported File Types

The following file types are supported for the Hive connector:

ORC
RCFile
TEXT
Parquet

Configuration

Presto includes Hive connectors for multiple versions of Hadoop:

hive-hadoop2: Apache Hadoop 2.x
hive-cdh5: Cloudera CDH 5

Create /etc/presto/catalog/hive.properties with the following contents to mount the hive-hadoop2 connector as the hive catalog, replacing hive-hadoop2 with the proper connector for your version of Hadoop and example.net:9083 with the correct host and port for your Hive metastore Thrift service:

connector.name=hive-hadoop2
hive.metastore.uri=thrift://example.net:9083

Additionally, you should add the following property to jvm.config, replacing <hdfs_username> with your hdfs user name:

-DHADOOP_USER_NAME=<hdfs_username>

Multiple Hive Clusters

You can have as many catalogs as you need, so if you have additional Hive clusters, simply add another properties file to /etc/presto/catalog with a different name (making sure it ends in .properties). For example, if you name the property file sales.properties, Presto will create a catalog named sales using the configured connector. If you are connecting to more than one Hive metastore, you can create any number of properties files configuring multiple instances of the Hive connector.

HDFS Configuration

Presto configures the HDFS client automatically for most setups and does not require any configuration files. In some rare cases, such as when using federated HDFS or high availability Hive, it may be necessary to specify additional HDFS client options in order to access your HDFS cluster. To do so, add the hive.config.resources property to reference your HDFS config files:

hive.config.resources=/etc/hadoop/conf/core-site.xml,/etc/hadoop/conf/hdfs-site.xml

Only specify additional configuration files if absolutely necessary. We also recommend reducing the configuration files to have the minimum set of required properties, as additional properties may cause problems.

HDFS Permissions

Before running any CREATE TABLE or CREATE TABLE ... AS statements for Hive tables in Presto, you need to check that the operating system user running the Presto server has access to the Hive warehouse directory on HDFS. The Hive warehouse directory is specified by the configuration variable hive.metastore.warehouse.dir in hive-site.xml, and the default value is /user/hive/warehouse. If that is not the case, either add the following to jvm.config on all of the nodes: -DHADOOP_USER_NAME=USER, where USER is an operating system user that has proper permissions for the Hive warehouse directory, or start the Presto server as a user with similar permissions. The hive user generally works as USER, since Hive is often started with the hive user. If you run into HDFS permissions problems on CREATE TABLE ... AS, remove /tmp/presto-* on HDFS, fix the user as described above, then restart all of the Presto servers.

Configuration Properties

Property Name	Description	Default
`hive.metastore.uri`	The URI(s) of the Hive Metastore to connect to using the Thrift protocol. If a comma-separated list of URIs is provided, the first URI is used by default, and the rest of the URIs are fallback Metastores. This property is required. Example: `thrift://192.0.2.3:9083` or `thrift://192.0.2.3:9083,thrift://192.0.2.4:9083`
`hive.config.resources`	An optional comma-separated list of HDFS configuration files. These files must exist on the machines running Presto. Only specify this if absolutely necessary to access HDFS. Example: `/etc/hdfs-site.xml`
`hive.storage-format`	The default file format used when creating new tables.	`RCBINARY`
`hive.force-local-scheduling`	Force splits to be scheduled on the same node as the Hadoop DataNode process serving the split data. This is useful for installations where Presto is collocated with every DataNode.	`false`
`hive.allow-drop-table`	Allow the Hive connector to drop tables.	`false`
`hive.allow-rename-table`	Allow the Hive connector to rename tables.	`false`

Querying Hive Tables

The following table is an example Hive table from the Hive Tutorial. It can be created in Hive (not in Presto) using the following Hive CREATE TABLE command:

hive> CREATE TABLE page_view (
    >   viewTime INT,
    >   userid BIGINT,
    >   page_url STRING,
    >   referrer_url STRING,
    >   ip STRING COMMENT 'IP Address of the User')
    > COMMENT 'This is the page view table'
    > PARTITIONED BY (dt STRING, country STRING)
    > STORED AS SEQUENCEFILE;
OK
Time taken: 3.644 seconds

Assuming that this table was created in the web schema in Hive, this table can be described in Presto:

DESCRIBE hive.web.page_view;

    Column    |  Type   | Null | Partition Key |        Comment
--------------+---------+------+---------------+------------------------
 viewtime     | bigint  | true | false         |
 userid       | bigint  | true | false         |
 page_url     | varchar | true | false         |
 referrer_url | varchar | true | false         |
 ip           | varchar | true | false         | IP Address of the User
 dt           | varchar | true | true          |
 country      | varchar | true | true          |
(7 rows)

This table can then be queried in Presto:

SELECT * FROM hive.web.page_view;

Custom Storage Handlers

Hive tables can use custom storage handlers to support alternative data formats. To query from Hive tables that use custom storage handlers, you will need the JARs containing the storage handler classes. Copy the storage handler JARs to the connector plugin directory on all nodes, restart the presto servers, and then query the table as you would any other Hive table. You can copy the jar across the cluster using presto-admin’s plugin add_jar command and restart servers by using the server restart command.

For example, if the plugin directory is located at /usr/lib/presto/lib/plugin, and you want to use the hive-hadoop2 connector to query from a table that uses a storage handler available in /tmp/my-classes.jar:

Copy my-classes.jar into /usr/lib/presto/lib/plugin/hive-hadoop2 on all nodes of the cluster.
```
sudo ./presto-admin plugin add_jar /tmp/my-classes.jar hive-hadoop2
```
Restart your presto-servers:
```
sudo ./presto-admin server restart
```

Then you can query from the table as you would any other Hive table in Presto.

Presto 0.115t Documentation