When running an information link a join database is used for creating temporary tables and joining the final result. When you specify a default join database, this is one possible join database. Spotfire can also search the information link query for a writable data source that can be used as a join database, or use any writable information services data source in the library.

Configure a default join database when you know that your data sources are read-only. You might also want to configure a default join database, for example, if you prefer to run these operations as a specific user on a certain database, or if you want to use a database that is optimized for temporary tables.

When you do not configure your own default join database you risk the join failing if you don’t have any writable database available in the library for the current user. To set up a default join database use the command create-join-db.

What database can I use as the default join database?

You can use a JDBC-compliant database of your choice as the default join database. You need the following to configure a database as the default join database

How can I decide what database to use for joins?

Spotfire chooses a join database according to certain selection rules. You can determine the order of these selection rules with the configuration property information-services.join-data-source-selection-rule in the Spotfire server configuration .

With the default settings, Spotfire first searches the data sources in the join for a suitable join database. If it cannot find a writable database then it will use the default join database, if configured.

If you always want to use your configured default join database, change the join-data-source-selection-rule setting to DEFAULT_JOIN_DATA_SOURCE. This modifies the selection order so that Spotfire tries to use the configured default join database first.

You can also determine the database that Spotfire should use for specific joins. In Information Designer, you can determine a join database on the Information link tab under Join path. Here, you can either select one of the data sources in your library, or you can select Use default. In this case, Spotfire follows the selection rules described above.

Table 1. Default join database settings

Option	Description
Type	Sets the type of database and driver you want to use as the default join database. Refers to a data source template.
Connection URL	The connection URL to the database.
Number of Connections	A minimum and maximum number of connections to use when accessing the database.
Username and Password	The username and password that will be used to access the database.