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PrestoDB

This page discusses how to make an Apache Presto connection, along with potential issues and workarounds.

Configuring a Connection

In the Admin section of Looker, navigate to the Connections page and click New Connection. Looker displays this page:

Fill out the page as follows:

Click Test These Settings to verify a connection. Looker will run a SELECT 1 query to verify a basic connection and perform a query test. It will not validate that the catalog and schema combination exists or that the user has access to it.

Click Update Connection to save these settings.

For more information about connection settings, see the Connections documentation page.

Configuring Apache Presto for PDTs

This section explains the necessary configuration settings for a scratch database.

Currently only Hive connectors are supported for PDTs. You may want to set up a separate Hive catalog properties file for the PDT scratch schema, or modify the existing Hive catalog properties file.

There are a few configuration properties and values that the Hive catalog properties file should contain.

The following is required because Presto caches the Hive metastore results, and Looker needs to be able to see the tables right away:

hive.metastore-cache-ttl = 0s

These two properties are required because Looker needs to be able to drop and rename PDTs:

hive.allow-rename-table=true

hive.allow-drop-table=true

For reference, in our internal Presto testing servers we use the following hive.properties file, which is used for all Hive schemas:

hive.s3.connect-timeout=1m hive.s3.max-backoff-time=10m hive.s3.max-error-retries=50 hive.metastore-cache-ttl = 0s hive.metastore-refresh-interval = 5s hive.s3.max-connections=500 hive.s3.max-client-retries=50 connector.name=hive-hadoop2 hive.s3.socket-timeout=2m hive.s3.staging-directory=/mnt/tmp/ hive.s3.use-instance-credentials=true hive.config.resources=/etc/hadoop/conf/core-site.xml,/etc/hadoop/conf/hdfs-site.xml hive.parquet.use-column-names=true hive.allow-drop-table=true hive.metastore.uri=thrift://:9083 hive.storage-format=ORC hive.allow-rename-table=true

Reference

For more information about configuring your Hive connector, see the Presto documentation.

Troubleshooting

If using EMR with a Hive 1.0.0 version, there is a bug in the permissions of /user/hive/warehouse that prevents ALTER TABLE...RENAME TO from working.

To fix it, change the ownership of that database’s directory to hive:hadoop from hadoop:hive, with something like:

hadoop dfs -chown hive:hadoop -R /user/hive/warehouse/scratch_db.db

See the Presto on EMR documentation for more detail.

Debugging

Feature Support

Looker’s ability to provide some features depends on whether the database dialect can support them.

In the current Looker release, PrestoDB supports the following Looker features:

Next Step

After you have connected your database to Looker, you’re ready to configure sign-in options for your users.

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