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>

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

Configuration Properties

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:

1. 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
   

2. 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.

Character data types

Hive supports three character data types:

• STRING
• CHAR(n)
• VARCHAR(n)

Currently columns for all those data types are exposed in presto as unparametrized VARCHAR type. This implies semantic inconsistencies for columns defined as CHAR(x) between Hive and Presto.

Following example documents basic semantic differences:

Create table in Hive

hive> create table string_test (c char(5), v varchar(5), s string) stored as orc;
hive> insert into string_test values ('ala', 'ala', 'ala'), ('ala ', 'ala ', 'ala ');

Query the table in Hive

hive> select concat('x', c, 'x'), concat('x', v, 'x'), concat('x', s, 'x'), length(c), length(v), length(s) from string_test;
OK
xalax       xalax    xalax   3      3       3
xalax       xala x   xala x  3      4       4

Query the table in Presto

presto:default> select concat('x',c,'x'), concat('x', v, 'x'), concat('x', s, 'x'), length(c), length(v), length(s) from string_test;
  _col0  | _col1  | _col2  | _col3 | _col4 | _col5
---------+--------+--------+-------+-------+-------
 xala  x | xalax  | xalax  |     5 |     3 |     3
 xala  x | xala x | xala x |     5 |     4 |     4

Also for CHAR(x) datatype padding whitespace should not be taken into consideration during comparisons. So 'ala  ' should be equal to 'ala        '. This is currently not the case in Presto.

Note: Ultimately Presto presto will implement native CHAR(x) data type. It will follow ANSI SQL semantics which differs from

Hive’s. This will cause backward incompatibilities of queries using Hive’s CHAR(x) columns.