What are Scheduled Queries?

Scheduled Queries in BigQuery allow users to run SQL tasks on a predefined, automated schedule.

Instead of manually initiating a query each day or week, BigQuery can do it for you. This is perfect for light orchestration of repetitive data transformations, updates, and regular reporting tasks.

Creating a Scheduled Query manually

A scheduled query can be created manually using the Schedule button in the Query window.

A dialog box is presented where we are prompted to provide the following information:

• a name for the scheduled query

• a scheduling option or the option to run it manually (on demand)

• start date and end date for which this query would run

• optionally, a destination dataset and table for the query result (including the possibility of adding a partitioning field)

• region selection

• encryption options

• principal (user or service account) to run the query under

• write disposition, in order words what to do with the contents already in the table: keep (and append new data) or overwrite (and replace with the new data)

• notification options

Creating a scheduled query using Terraform

A schedule can also be created using Terraform, as per the following example.

This option provides a subset of options from the manual method - at the time of writing, for example, the write disposition cannot be set up here.

variable "envConfig" {

    type = map(object({
        project_id = string
        service_account_name = string
    }))
}

variable "config" {
    type = map(object({
        name = string
        query = string
        destination_table_name_template = string
    }))
}

resource "google_bigquery_data_transfer_config" "query_config" {
    for_each = var.config
    display_name = each.value["name"]
    location = "europe"
    data_source_id = "scheduled_query"
    schedule = "every saturday 05:00"
    destination_dataset_id = "learning"
    params = {
        destination_table_name_template = each.value["destination_table_name_template"]
        write_disposition = "WRITE_APPEND"
        query = each.value["query"]
    }
    service_account_name = var.envConfig["dev"].service_account_name
    project = var.envConfig["dev"].project_id
}

Creating a Scheduled Query using the API

It's also possible to create a scheduled query using one of the BigQuery APIs or the bq CLI command - check the GCP documentation here.

Viewing scheduled queries

Viewing the scheduled query can be done by Accessing the 'Scheduled queries' option in the BigQuery subgroup.

It will display a list of queries, their schedule, region, destination (if any) and next run time.

Click on a particular query would present a Run history and its output. There is also an option for scheduling a backfill (which we can use for a Manual Run).

Clicking on the Configuration tab would display the configurations used to create the query.

In conclusion, BigQuery Scheduled queries can be a useful tool in your toolset, as a quick and easy way to do light orchestration of SQL tasks.

Thanks for reading!

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