Run multiple BigQuery jobs in parallel

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BigQuery hosts a number of public datasets that are available to the general public to query. In this tutorial, you create a workflow that runs multiple BigQuery query jobs in parallel, demonstrating an improvement in performance when compared to running the jobs serially, one after the other.

Objectives

In this tutorial you will:

1. Run a query against a Wikipedia public dataset to determine the most viewed titles in a specific month.
2. Deploy and execute a workflow that runs multiple BigQuery query jobs serially, one after the other.
3. Deploy and execute a workflow that runs the BigQuery jobs using parallel iteration, and where ordinary for loops are executed in parallel.

You can run the following commands in the Google Cloud console, or by using the Google Cloud CLI in either your terminal or Cloud Shell.

Costs

In this document, you use the following billable components of Google Cloud:

• BigQuery
• Workflows

To generate a cost estimate based on your projected usage, use the pricing calculator. New Google Cloud users might be eligible for a free trial.

Before you begin

Security constraints defined by your organization might prevent you from completing the following steps. For troubleshooting information, see Develop applications in a constrained Google Cloud environment.

Console

1. Sign in to your Google Cloud account. If you're new to Google Cloud, create an account to evaluate how our products perform in real-world scenarios. New customers also get $300 in free credits to run, test, and deploy workloads.

2. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

   Note: If you don't plan to keep the resources that you create in this procedure, create a project instead of selecting an existing project. After you finish these steps, you can delete the project, removing all resources associated with the project.

   Go to project selector

3. Make sure that billing is enabled for your Google Cloud project.

4. Enable the Workflows API.

   Enable the API

5. Create a service account:

   1. In the Google Cloud console, go to the Create service account page.

      Go to Create service account
   2. Select your project.

   3. In the Service account name field, enter a name. The Google Cloud console fills in the Service account ID field based on this name.

      In the Service account description field, enter a description. For example, Service account for quickstart.

   4. Click Create and continue.

   5. Grant the following roles to the service account: BigQuery > BigQuery Job User, Logging > Logs Writer.

      To grant a role, find the Select a role list, then select the role.

      To grant additional roles, click Add another role and add each additional role.

      Note: The Role field affects which resources the service account can access in your project. You can revoke these roles or grant additional roles later. In production environments, do not grant the Owner, Editor, or Viewer roles. Instead, grant a predefined role or custom role that meets your needs.
   6. Click Continue.

   7. Click Done to finish creating the service account.

6. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

   Note: If you don't plan to keep the resources that you create in this procedure, create a project instead of selecting an existing project. After you finish these steps, you can delete the project, removing all resources associated with the project.

   Go to project selector

7. Make sure that billing is enabled for your Google Cloud project.

8. Enable the Workflows API.

   Enable the API

9. Create a service account:

   1. In the Google Cloud console, go to the Create service account page.

      Go to Create service account
   2. Select your project.

   3. In the Service account name field, enter a name. The Google Cloud console fills in the Service account ID field based on this name.

      In the Service account description field, enter a description. For example, Service account for quickstart.

   4. Click Create and continue.

   5. Grant the following roles to the service account: BigQuery > BigQuery Job User, Logging > Logs Writer.

      To grant a role, find the Select a role list, then select the role.

      To grant additional roles, click Add another role and add each additional role.

      Note: The Role field affects which resources the service account can access in your project. You can revoke these roles or grant additional roles later. In production environments, do not grant the Owner, Editor, or Viewer roles. Instead, grant a predefined role or custom role that meets your needs.
   6. Click Continue.

   7. Click Done to finish creating the service account.

gcloud

1. Sign in to your Google Account.

   If you don't already have one, sign up for a new account.

2. Install the Google Cloud CLI.

3. To initialize the gcloud CLI, run the following command:

   gcloud init

4. Create or select a Google Cloud project.

   Note: If you don't plan to keep the resources that you create in this procedure, create a project instead of selecting an existing project. After you finish these steps, you can delete the project, removing all resources associated with the project.

   • Create a Google Cloud project:

     gcloud projects create PROJECT_ID

     Replace PROJECT_ID with a name for the Google Cloud project you are creating.

   • Select the Google Cloud project that you created:

     gcloud config set project PROJECT_ID

     Replace PROJECT_ID with your Google Cloud project name.

5. Make sure that billing is enabled for your Google Cloud project.

6. Enable the Workflows API:

   gcloud services enable workflows.googleapis.com

7. Set up authentication:

   1. Create the service account:

      gcloud iam service-accounts create SERVICE_ACCOUNT_NAME

      Replace SERVICE_ACCOUNT_NAME with a name for the service account.

   2. Grant roles to the service account. Run the following command once for each of the following IAM roles: roles/bigquery.jobUser, roles/logging.logWriter:

      gcloud projects add-iam-policy-binding PROJECT_ID --member="serviceAccount:SERVICE_ACCOUNT_NAME@PROJECT_ID.iam.gserviceaccount.com" --role=ROLE

      Replace the following:

      • SERVICE_ACCOUNT_NAME: the name of the service account
      • PROJECT_ID: the project ID where you created the service account
      • ROLE: the role to grant
      Note: The --role flag affects which resources the service account can access in your project. You can revoke these roles or grant additional roles later. In production environments, do not grant the Owner, Editor, or Viewer roles. Instead, grant a predefined role or custom role that meets your needs.
8. Install the Google Cloud CLI.

9. To initialize the gcloud CLI, run the following command:

   gcloud init

10. Create or select a Google Cloud project.

    Note: If you don't plan to keep the resources that you create in this procedure, create a project instead of selecting an existing project. After you finish these steps, you can delete the project, removing all resources associated with the project.

    • Create a Google Cloud project:

      gcloud projects create PROJECT_ID

      Replace PROJECT_ID with a name for the Google Cloud project you are creating.

    • Select the Google Cloud project that you created:

      gcloud config set project PROJECT_ID

      Replace PROJECT_ID with your Google Cloud project name.

11. Make sure that billing is enabled for your Google Cloud project.

12. Enable the Workflows API:

    gcloud services enable workflows.googleapis.com

13. Set up authentication:

    1. Create the service account:

       gcloud iam service-accounts create SERVICE_ACCOUNT_NAME

       Replace SERVICE_ACCOUNT_NAME with a name for the service account.

    2. Grant roles to the service account. Run the following command once for each of the following IAM roles: roles/bigquery.jobUser, roles/logging.logWriter:

       gcloud projects add-iam-policy-binding PROJECT_ID --member="serviceAccount:SERVICE_ACCOUNT_NAME@PROJECT_ID.iam.gserviceaccount.com" --role=ROLE

       Replace the following:

       • SERVICE_ACCOUNT_NAME: the name of the service account
       • PROJECT_ID: the project ID where you created the service account
       • ROLE: the role to grant
       Note: The --role flag affects which resources the service account can access in your project. You can revoke these roles or grant additional roles later. In production environments, do not grant the Owner, Editor, or Viewer roles. Instead, grant a predefined role or custom role that meets your needs.

Run a BigQuery query job

In BigQuery, you can run an interactive (on-demand) query job. For more information, see Running interactive and batch query jobs.

Console

1. In the Google Cloud console, go to the BigQuery page.

   Go to BigQuery

2. Enter the following BigQuery SQL query in the Query editor text area:

   SELECT TITLE, SUM(views)
   FROM `bigquery-samples.wikipedia_pageviews.201207h`
   GROUP BY TITLE
   ORDER BY SUM(views) DESC
   LIMIT 100
   

3. Click Run.

bq

In your terminal, enter the following bq query command to run an interactive query using standard SQL syntax:

bq query \
--use_legacy_sql=false \
'SELECT
  TITLE, SUM(views)
FROM
  `bigquery-samples.wikipedia_pageviews.201207h`
GROUP BY
  TITLE
ORDER BY
  SUM(views) DESC
LIMIT 100'

This runs a query that returns the top 100 Wikipedia titles with the most views in a specific month and writes the output to a temporary table.

Note how long the query takes to run.

Deploy a workflow that runs multiple queries serially

A workflow definition is made up of a series of steps described using the Workflows syntax. After creating a workflow, you deploy it to make it available for execution. The deploy step also validates that the source file can be executed.

The following workflow defines a list of five tables to run a query against using the Workflows BigQuery connector. The queries are run serially, one after the other, and the most viewed titles from each table are saved to a results map.

Console

1. In the Google Cloud console, go to the Workflows page:

   Go to Workflows

2. Click Create.

3. Enter a name for the new workflow, such as workflow-serial-bqjobs.

4. Choose an appropriate region; for example, us-central1.

5. Select the service account you previously created.

   You should have already granted both the BigQuery > BigQuery Job User and Logging > Logs Writer IAM roles to the service account.

6. Click Next.

7. In the workflow editor, enter the following definition for your workflow:

   main:
       steps:
       - init:
           assign:
               - results : {} # result from each iteration keyed by table name
               - tables:
                   - 201201h
                   - 201202h
                   - 201203h
                   - 201204h
                   - 201205h
       - runQueries:
           for:
               value: table
               in: ${tables}
               steps:
               - logTable:
                   call: sys.log
                   args:
                       text: ${"Running query for table " + table}
               - runQuery:
                   call: googleapis.bigquery.v2.jobs.query
                   args:
                       projectId: ${sys.get_env("GOOGLE_CLOUD_PROJECT_ID")}
                       body:
                           useLegacySql: false
                           useQueryCache: false
                           timeoutMs: 30000
                           # Find top 100 titles with most views on Wikipedia
                           query: ${
                               "SELECT TITLE, SUM(views)
                               FROM `bigquery-samples.wikipedia_pageviews." + table + "`
                               WHERE LENGTH(TITLE) > 10
                               GROUP BY TITLE
                               ORDER BY SUM(VIEWS) DESC
                               LIMIT 100"
                               }
                   result: queryResult
               - returnResult:
                   assign:
                       # Return the top title from each table
                       - results[table]: {}
                       - results[table].title: ${queryResult.rows[0].f[0].v}
                       - results[table].views: ${queryResult.rows[0].f[1].v}
       - returnResults:
           return: ${results}

8. Click Deploy.

gcloud

1. Open a terminal and create a source code file for your workflow:

   touch workflow-serial-bqjobs.yaml
   

2. Copy the following workflow to your source code file:

   main:
       steps:
       - init:
           assign:
               - results : {} # result from each iteration keyed by table name
               - tables:
                   - 201201h
                   - 201202h
                   - 201203h
                   - 201204h
                   - 201205h
       - runQueries:
           for:
               value: table
               in: ${tables}
               steps:
               - logTable:
                   call: sys.log
                   args:
                       text: ${"Running query for table " + table}
               - runQuery:
                   call: googleapis.bigquery.v2.jobs.query
                   args:
                       projectId: ${sys.get_env("GOOGLE_CLOUD_PROJECT_ID")}
                       body:
                           useLegacySql: false
                           useQueryCache: false
                           timeoutMs: 30000
                           # Find top 100 titles with most views on Wikipedia
                           query: ${
                               "SELECT TITLE, SUM(views)
                               FROM `bigquery-samples.wikipedia_pageviews." + table + "`
                               WHERE LENGTH(TITLE) > 10
                               GROUP BY TITLE
                               ORDER BY SUM(VIEWS) DESC
                               LIMIT 100"
                               }
                   result: queryResult
               - returnResult:
                   assign:
                       # Return the top title from each table
                       - results[table]: {}
                       - results[table].title: ${queryResult.rows[0].f[0].v}
                       - results[table].views: ${queryResult.rows[0].f[1].v}
       - returnResults:
           return: ${results}

3. Deploy the workflow by entering the following command:

   gcloud workflows deploy workflow-serial-bqjobs \
      --source=workflow-serial-bqjobs.yaml \
      --service-account=MY_SERVICE_ACCOUNT@MY_PROJECT.IAM.GSERVICEACCOUNT.COM
   

   Replace MY_SERVICE_ACCOUNT@MY_PROJECT.IAM.GSERVICEACCOUNT.COM with the email of the service account you previously created.

   You should have already granted both the roles/bigquery.jobUser and roles/logging.logWriter IAM roles to the service account.

Execute the workflow and run multiple queries serially

Executing a workflow runs the current workflow definition associated with the workflow.

Console

1. In the Google Cloud console, go to the Workflows page:

   Go to Workflows

2. On the Workflows page, select the workflow-serial-bqjobs workflow to go to its details page.

3. On the Workflow Details page, click Execute.

4. Click Execute again.

5. View the results of the workflow in the Output pane.

gcloud

1. Open a terminal.

2. Execute the workflow:

    gcloud workflows run workflow-serial-bqjob

The workflow execution should take approximately a minute or five times the previous running time. The result will include each table and look similar to the following:

{
  "201201h": {
    "title": "Special:Search",
    "views": "14591339"
  },
  "201202h": {
    "title": "Special:Search",
    "views": "132765420"
  },
  "201203h": {
    "title": "Special:Search",
    "views": "123316818"
  },
  "201204h": {
    "title": "Special:Search",
    "views": "116830614"
  },
  "201205h": {
    "title": "Special:Search",
    "views": "131357063"
  }
}

Deploy and execute a workflow that runs multiple queries in parallel

Instead of running five queries sequentially, you can run the queries in parallel by making a few changes:

 - runQueries:
    parallel:
        shared: [results]
        for:
            value: table
            in: ${tables}

• A parallel step allows each iteration of the for loop to run in parallel.

• The results variable is declared as shared which allows it to be writable by a branch, and the result of each branch can be appended to it.

Console

1. In the Google Cloud console, go to the Workflows page:

   Go to Workflows

2. Click Create.

3. Enter a name for the new workflow, such as workflow-parallel-bqjobs.

4. Choose an appropriate region; for example, us-central1.

5. Select the service account you previously created.

6. Click Next.

7. In the workflow editor, enter the following definition for your workflow:

   main:
       steps:
       - init:
           assign:
               - results : {} # result from each iteration keyed by table name
               - tables:
                   - 201201h
                   - 201202h
                   - 201203h
                   - 201204h
                   - 201205h
       - runQueries:
           parallel:
               shared: [results]
               for:
                   value: table
                   in: ${tables}
                   steps:
                   - logTable:
                       call: sys.log
                       args:
                           text: ${"Running query for table " + table}
                   - runQuery:
                       call: googleapis.bigquery.v2.jobs.query
                       args:
                           projectId: ${sys.get_env("GOOGLE_CLOUD_PROJECT_ID")}
                           body:
                               useLegacySql: false
                               useQueryCache: false
                               timeoutMs: 30000
                               # Find top 100 titles with most views on Wikipedia
                               query: ${
                                   "SELECT TITLE, SUM(views)
                                   FROM `bigquery-samples.wikipedia_pageviews." + table + "`
                                   WHERE LENGTH(TITLE) > 10
                                   GROUP BY TITLE
                                   ORDER BY SUM(VIEWS) DESC
                                   LIMIT 100"
                                   }
                       result: queryResult
                   - returnResult:
                       assign:
                           # Return the top title from each table
                           - results[table]: {}
                           - results[table].title: ${queryResult.rows[0].f[0].v}
                           - results[table].views: ${queryResult.rows[0].f[1].v}
       - returnResults:
           return: ${results}

8. Click Deploy.

9. On the Workflow Details page, click Execute.

10. Click Execute again.

11. View the results of the workflow in the Output pane.

gcloud

1. Open a terminal and create a source code file for your workflow:

   touch workflow-parallel-bqjobs.yaml
   

2. Copy the following workflow to your source code file:

   main:
       steps:
       - init:
           assign:
               - results : {} # result from each iteration keyed by table name
               - tables:
                   - 201201h
                   - 201202h
                   - 201203h
                   - 201204h
                   - 201205h
       - runQueries:
           parallel:
               shared: [results]
               for:
                   value: table
                   in: ${tables}
                   steps:
                   - logTable:
                       call: sys.log
                       args:
                           text: ${"Running query for table " + table}
                   - runQuery:
                       call: googleapis.bigquery.v2.jobs.query
                       args:
                           projectId: ${sys.get_env("GOOGLE_CLOUD_PROJECT_ID")}
                           body:
                               useLegacySql: false
                               useQueryCache: false
                               timeoutMs: 30000
                               # Find top 100 titles with most views on Wikipedia
                               query: ${
                                   "SELECT TITLE, SUM(views)
                                   FROM `bigquery-samples.wikipedia_pageviews." + table + "`
                                   WHERE LENGTH(TITLE) > 10
                                   GROUP BY TITLE
                                   ORDER BY SUM(VIEWS) DESC
                                   LIMIT 100"
                                   }
                       result: queryResult
                   - returnResult:
                       assign:
                           # Return the top title from each table
                           - results[table]: {}
                           - results[table].title: ${queryResult.rows[0].f[0].v}
                           - results[table].views: ${queryResult.rows[0].f[1].v}
       - returnResults:
           return: ${results}

3. Deploy the workflow by entering the following command:

   gcloud workflows deploy workflow-parallell-bqjobs \
      --source=workflow-parallel-bqjobs.yaml \
      --service-account=MY_SERVICE_ACCOUNT@MY_PROJECT.IAM.GSERVICEACCOUNT.COM
   

   Replace MY_SERVICE_ACCOUNT@MY_PROJECT.IAM.GSERVICEACCOUNT.COM with the email of the service account you previously created.

4. Execute the workflow:

    gcloud workflows run workflow-serial-bqjob

The result will be similar to the previous output but the workflow execution should take approximately twenty seconds or less!

Clean up

If you created a new project for this tutorial, delete the project. If you used an existing project and wish to keep it without the changes added in this tutorial, delete resources created for the tutorial.

Delete the project

The easiest way to eliminate billing is to delete the project that you created for the tutorial.

To delete the project:

Caution: Deleting a project has the following effects:

• Everything in the project is deleted. If you used an existing project for the tasks in this document, when you delete it, you also delete any other work you've done in the project.
• Custom project IDs are lost. When you created this project, you might have created a custom project ID that you want to use in the future. To preserve the URLs that use the project ID, such as an appspot.com URL, delete selected resources inside the project instead of deleting the whole project.

If you plan to explore multiple architectures, tutorials, or quickstarts, reusing projects can help you avoid exceeding project quota limits.

1. In the Google Cloud console, go to the Manage resources page.

   Go to Manage resources

2. In the project list, select the project that you want to delete, and then click Delete.
3. In the dialog, type the project ID, and then click Shut down to delete the project.

Delete tutorial resources

Delete the workflows created in this tutorial:

gcloud workflows delete WORKFLOW_NAME

What's next

• To learn more about parallel steps, see Execute parallel steps.
• To learn more about Workflows connectors, see Understand connectors.
• To learn more about Workflows, see the Workflows overview.