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Connecting Looker to Your Database

After you have secured and configured your database, you’re ready to connect your database to Looker.

Creating a New Database Connection

Select Admin > Connections (under Database). On the Connections page, click New Connection:

Connection Settings

Looker displays the Connection Settings page:

The fields that the Connection Settings page displays depend on your dialect setting. The example above shows the configurable connection settings for Amazon Redshift.

For more information about applying user attributes to connection settings, see the “Connections” section of the User Attributes page.

For more information about using the PDT Overrides column to configure separate login credentials for PDT processes, see the Configuring Separate Login Credentials for PDT Processes section.

The following options are available for configuration when connecting Looker to Amazon Redshift.

Name

The name of the connection as you want to refer to it. You should not use the name of any Spaces. This value does not need to match anything in your database; it is just a label that you assign. You’ll use it in the connection parameter of your LookML model.

Dialect

The SQL dialect that matches your connection. It’s important to choose the correct value so that you are presented with the proper connection options, and so that Looker can properly translate your LookML into SQL.

Host:Port

Your database hostname and the port that Looker should use to connect to your database host.

If you apply a user attribute to the Host field, the user attribute cannot have a user access level set to Editable.

Database

The name of the database on your host. For example, you might have a host name of my-instance.us-east-1.redshift.amazonaws.com on which there is a database called sales_info. You would enter sales_info in this field. If you have multiple databases on the same host, you may need to create multiple connections to use them (with the exception of MySQL, in which the word “database” means something a little bit different than in most SQL dialects).

Username

The username that Looker should use to connect to your database. You should configure the user ahead of time according to our database configuration instructions.

Password

The password that Looker should use to connect to your database. You should configure the password ahead of time according to our database configuration instructions.

Schema

The default schema that Looker uses when a schema is not specified. This applies when using SQL Runner, during LookML project generation, and when querying tables.

Persistent Derived Tables

Check this box to enable persistent derived tables. This reveals the Temp Database field and the PDT Overrides column. Looker displays this option only if the database dialect you chose supports using PDTs.

Temp Database

Although this is labeled Temp Database, you’ll enter either the database name or schema name — as appropriate for your SQL dialect — that Looker should use to create persistent derived tables. You should configure this database or schema ahead of time, with the appropriate write permissions. On the Database Configuration Instructions documentation page, select your database dialect to see the instructions for that dialect.

Each connection must have its own Temp Database or Schema; they cannot be shared across connections.

Additional Params

You can include additional Java Database Connectivity (JDBC) parameters for your queries here, if needed.

If you want to use a user attribute in a JDBC parameter, you can use Liquid templating. The syntax is _user_attributes['name_of_your_user_attribute']. For example:

my_jdbc_param={{ _user_attributes['name_of_attribute'] }}

Here’s how it might look in the Additional Params field in Looker:

PDT and Datagroup Maintenance Schedule

This setting accepts a cron expression that indicates when Looker should check datagroups and persistent derived tables (that are based on sql_trigger_value) to be regenerated or dropped.

The default value of */5 * * * * means “check every 5 minutes,” which is the maximum frequency of checks. A cron expression indicating more frequent checks will cause checks to occur every 5 minutes.

If your database isn’t up 24/7, you may want to limit checks to times when the database is up. Here are some additional cron expressions:

cron expresssion Definition
*/5 8-17 * * MON-FRI Check datagroups and PDTs every 5 minutes during business hours, Monday through Friday
*/5 8-17 * * * Check datagroups and PDTs every 5 minutes during business hours, every day
0 8-17 * * MON-FRI Check datagroups and PDTs every hour during business hours, Monday through Friday
1 3 * * * Check datagroups and PDTs every day at 3:01am

A few things to note when creating a cron expression:

Below are a couple of resources to assist with creating cron strings:

SSL

Choose whether or not you want to use SSL encryption to protect data as it passes between Looker and your database. SSL is only one option that can be used to protect your data; other secure options are described on the Enabling Secure Database Access documentation page.

Verify SSL Cert

Choose whether you want to require verification of the SSL certificate used by the connection. If verification is required, the SSL Certificate Authority (CA) that signed the SSL certificate must come from the client’s list of trusted sources. If the CA is not a trusted source, the database connection is not established.

If this box is unchecked, SSL encryption is still used on the connection, but verification of the SSL connection is not required, so a connection can be established when the CA is not on the client’s list of trusted sources.

Max Connections

Here you can set the maximum number of connections that Looker can establish with your database. For the most part, you are setting the number of simultaneous queries that Looker can run against your database. Looker also reserves up to three connections for query killing. If the connection pool is very small, then Looker will reserve fewer connections.

You should set this value carefully. If the value is too high, you may overwhelm your database. If the value is too low, then queries have to share a small number of connections. Thus many queries may seem slow to users as the queries have to wait for other, earlier queries to return.

The default value (which varies depending upon your SQL dialect) is typically a reasonable starting point. Most databases also have their own settings for the maximum number of connections they will accept. If your database configuration limits connections, ensure that your Max Connections value is equal to or lower than your database’s limit.

Connection Pool Timeout

If your users do request more connections than the Max Connections setting, the requests will wait for others to finish before they are executed. The maximum amount of time that a request will wait is configured here. You should set this value carefully. If it is too low, users may find their queries get cancelled because there isn’t enough time for other user’s queries to finish. If it is too high, large numbers of queries may build up causing users to wait for a very long time. The default value is typically a reasonable starting point.

SQL Runner Precache

In SQL Runner, all table information is pre-loaded as soon as you select a connection and schema. This enables SQL Runner to quickly display table columns as soon as you click on a table name. However, for connections and schema with many tables or with very large tables, you may not want SQL Runner to pre-load all of the information.

If you prefer SQL Runner to load table information only when a table is selected, you can uncheck the SQL Runner Precache option to disable SQL Runner pre-loading for the connection.

Database Time Zone

The time zone in which your database stores time-based information. Looker needs to know this so that it can convert time values for users, making it easier to understand and use time-based data. See the Using Time Zone Settings documentation page for more information.

Query Time Zone

The Query Time Zone option is visible only if you have disabled User Specific Time Zones.

When User Specific Time Zones are disabled, the Query Time Zone is the time zone that is displayed to your users when they query time-based data, and the time zone into which Looker will convert time-based data from the Database Time Zone.

See the Using Time Zone Settings documentation page for more information.

Configuring Separate Login Credentials for PDT Processes

If your database supports persistent derived tables, and you have checked the Persistent Derived Tables box in the connection settings, Looker displays the PDT Overrides column. In the PDT Overrides column, you can enter separate JDBC parameters (host, port, database, username, password, schema, and additional parameters) that are specific to PDT processes. This can be valuable for a number of reasons:

For example, the configuration below shows a connection where the username and password fields are set to user attributes. This way, each user can access the database using their individual credentials. The PDT Override column creates a separate user (pdt_user) with its own password. The pdt_user account will be used for all PDT processes, with access levels appropriate to PDT creation and update:

While the PDT Overrides column enables you to change the database user and other connection properties, any overrides must still use the same connection. Looker cannot read data from one location and write it to another; a PDT override must read the same data as the default connection, and it must write data to the same place.

Testing Your Connection Settings

Once you’ve entered the credentials, click on Test These Settings to verify that the information is correct and that the database is able to connect:

If your connection does not pass one or more tests, try some of the troubleshooting steps on the Testing Database Connectivity documentation page.

If you are running Mongo version 3.6 or below on Atlas and you get a communications link failure, see the Mongo Connector documentation page.

If you are still having trouble, contact Looker support for assistance.

To receive successful connection messages regarding the temp schema and PDTs, you will have needed to allow that functionality when you set up your Looker database. Instructions for doing so are found Database Configuration Instructions documentation page.

Adding Your Database Connection

Once you have configured and tested your database connection settings, click Add Connection. Your database connection is now added to the list on the Connections page.

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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