Introduction to sessions

This guide describes how to enable, create, and track changes in a BigQuery session. It is intended for users who are familiar with BigQuery and GoogleSQL.

You can capture your SQL activities in a BigQuery session. Temporary tables, temporary functions, and variables can be used throughout the session to interactively build one or more queries. Multiple sessions can be active at the same time and the history for each session is saved. You can view the history of a session for up to 20 days after the session is terminated.

Typical uses for a session include the following:

• Maintain transient session data. Define variables and temporary tables once and use them throughout the session.

• Look up query history by session. If you want to keep track of a behavior that happened at a particular time during the session, you can view the history of changes that were made during the session.

• Create multi-statement transactions over multiple queries. Within a session, you can begin a transaction, make changes, and view the temporary result before deciding to commit or rollback. You can do this over several queries in the session. If you do not use a session, a multi-statement transaction needs to be completed in a single query.

Pricing

• There are no additional costs for using sessions.

• For projects that use on-demand pricing, queries against INFORMATION_SCHEMA incur charges. For more information, see INFORMATION_SCHEMA pricing.

• You are charged for temporary tables that you create in sessions. Storage charges are based on how much data is stored in the tables. For information about storage pricing, see Storage pricing.

Limitations

• Every query in a session is run in the location where the session was created.

• A session is currently automatically terminated after 24-hours of inactivity.

• A session is currently automatically terminated 7 days after its creation.

• The maximum size of a session variable is 1 MB, and the maximum size of all variables used in a session is 10 MB.

• No concurrent queries are allowed in the same session.

Roles and permissions

This section describes the Identity and Access Management (IAM) permissions and the IAM roles that you need to perform actions with sessions.

What's next

• Creating sessions