Manage partition and cluster recommendations

This document describes how the partition and cluster recommender works, how to view your recommendations and insights, and how can apply partition and cluster recommendations.

How the recommender works

The BigQuery partitioning and clustering recommender generates partition or cluster recommendations to optimize your BigQuery tables. The recommender analyzes workflows on your BigQuery tables and offers recommendations to better optimize your workflows and query costs using either table partitioning or table clustering.

For more information about the Recommender service, see the Recommender overview.

The partitioning and clustering recommender uses the project's workload execution data from the past 30 days to analyze each BigQuery table for suboptimal partitioning and clustering configurations. The recommender also uses machine learning to predict how much the workload execution could be optimized with different partitioning or clustering configurations. If the recommender finds that partitioning or clustering a table yields significant savings, the recommender generates a recommendation. The partitioning and clustering recommender generates the following types of recommendations:

Existing table type	Recommendation subtype	Recommendation example
Non-partitioned, non-clustered	Partition	"Save about 64 slot hours per month by partitioning on column_C by DAY"
Non-partitioned, non-clustered	Cluster	"Save about 64 slot hours per month by clustering on column_C"
Partitioned, non-clustered	Cluster	"Save about 64 slot hours per month by clustering on column_C"

Each recommendation consists of three parts:

• Guidance to either partition or cluster a specific table
• The specific column in a table to partition or cluster
• Estimated monthly savings for applying the recommendation

To calculate potential workload savings, the recommender assumes that the historical execution workload data from the past 30 days represents the future workload.

The recommender API also returns table workload information in the form of insights. Insights are findings that help you understand your project's workload, providing more context on how a partition or cluster recommendation might improve workload costs.

Limitations

• The partitioning and clustering recommender does not support BigQuery tables with legacy SQL. When generating a recommendation, the recommender excludes any legacy SQL queries in its analysis. Additionally, applying partition recommendations on BigQuery tables with legacy SQL breaks any legacy SQL workflows in that table.

  Before you apply partition recommendations, migrate your legacy SQL workflows into GoogleSQL.

• BigQuery does not support changing the partitioning scheme of a table in place. You can only change the partitioning of a table on a copy of the table. For more information, see Apply partition recommendations.

Locations

The partitioning and clustering recommender is available in the following processing locations:

	Region description	Region name	Details
Asia Pacific
	Delhi	asia-south2
	Hong Kong	asia-east2
	Jakarta	asia-southeast2
	Mumbai	asia-south1
	Osaka	asia-northeast2
	Seoul	asia-northeast3
	Singapore	asia-southeast1
	Sydney	australia-southeast1
	Taiwan	asia-east1
	Tokyo	asia-northeast1
Europe
	Belgium	europe-west1	Low CO2
	Berlin	europe-west10	Low CO2
	EU multi-region	eu
	Frankfurt	europe-west3	Low CO2
	London	europe-west2	Low CO2
	Netherlands	europe-west4	Low CO2
	Zürich	europe-west6	Low CO2
Americas
	Iowa	us-central1	Low CO2
	Las Vegas	us-west4
	Los Angeles	us-west2
	Montréal	northamerica-northeast1	Low CO2
	Northern Virginia	us-east4
	Oregon	us-west1	Low CO2
	Salt Lake City	us-west3
	São Paulo	southamerica-east1	Low CO2
	Toronto	northamerica-northeast2	Low CO2
	US multi-region	us

Before you begin

• Ensure that Gemini in BigQuery is enabled for your Google Cloud project.
• Enable the Recommender API.

Required permissions

To get the permissions that you need to access partition and cluster recommendations, ask your administrator to grant you the BigQuery Partitioning Clustering Recommender Viewer (roles/recommender.bigqueryPartitionClusterViewer) IAM role. For more information about granting roles, see Manage access to projects, folders, and organizations.

This predefined role contains the permissions required to access partition and cluster recommendations. To see the exact permissions that are required, expand the Required permissions section:

Required permissions

The following permissions are required to access partition and cluster recommendations:

• recommender.bigqueryPartitionClusterRecommendations.get
• recommender.bigqueryPartitionClusterRecommendations.list

You might also be able to get these permissions with custom roles or other predefined roles.

For more information about IAM roles and permissions in BigQuery, see Introduction to IAM.

View recommendations

This section describes how to view partition and cluster recommendations and insights using the Google Cloud console, the Google Cloud CLI, or the Recommender API.

Note: You can also export recommendations to BigQuery using the BigQuery Data Transfer Service. For more information, see Export recommendations to BigQuery.

Select one of the following options:

Console

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

   Go to BigQuery

2. To open the recommendations tab, click Recommendations > View all recommendations.

   

   The recommendations tab lists all recommendations available to your project.

3. In the Optimize BigQuery workload cost panel, click View all.

   The cost recommendation table lists all recommendations generated for the current project. For example, the following screenshot shows that the recommender analyzed the example_table table, and then recommended clustering the example_column column to save an approximate amount of bytes and slots.

   

4. To see more information about the table insight and recommendation, click a recommendation.

gcloud

To view partition or cluster recommendations for a specific project, use the gcloud recommender recommendations list command:

gcloud recommender recommendations list \
    --project=PROJECT_NAME \
    --location=REGION_NAME \
    --recommender=google.bigquery.table.PartitionClusterRecommender \
    --format=FORMAT_TYPE \

Replace the following:

• PROJECT_NAME: the name of the project that contains your BigQuery table
• REGION_NAME: the region that your project is in
• FORMAT_TYPE: a supported gcloud CLI output format—for example, JSON

The following table describes the important fields from the recommender API response:

Property	Relevant for subtype	Description
recommenderSubtype	Partition or cluster	Indicates the type of recommendation.
content.overview.partitionColumn	Partition	Recommended partitioning column name.
content.overview.partitionTimeUnit	Partition	Recommended partitioning time unit. For example, DAY means the recommendation is to have daily partitions on the recommended column.
content.overview.clusterColumns	Cluster	Recommended clustering column names.

• For more information about other fields in the recommender response, see REST Resource: projects.locations.recommendersrecommendation.
• For more information about using the Recommender API, see Using the API - Recommendations.

To view table insights using the gcloud CLI, use the gcloud recommender insights list command:

gcloud recommender insights list \
    --project=PROJECT_NAME \
    --location=REGION_NAME \
    --insight-type=google.bigquery.table.StatsInsight \
    --format=FORMAT_TYPE \

Replace the following:

• PROJECT_NAME: the name of the project that contains your BigQuery table
• REGION_NAME: the region that your project is in
• FORMAT_TYPE: a supported gcloud CLI output format—for example, JSON

The following table describes the important fields from the insights API response:

Property	Relevant for subtype	Description
content.existingPartitionColumn	Cluster	Existing partitioning column, if any
content.tableSizeTb	All	Size of the table in terabytes
content.bytesReadMonthly	All	Monthly bytes read from the table
content.slotMsConsumedMonthly	All	Monthly slot milliseconds consumed by the workload running on the table
content.queryJobsCountMonthly	All	Monthly count of jobs running on the table

• For more information about other fields in the insights response, see REST Resource: projects.locations.insightTypes.insights.
• For more information about using insights, see Using the API - Insights.

REST API

To view partition or cluster recommendations for a specific project, use the REST API. With each command, you must provide an authentication token, which you can get using the gcloud CLI. For more information about getting an authentication token, see Methods for getting an ID token.

You can use the curl list request to view all recommendations for a specific project:

curl
    -H "Authorization: Bearer $GCLOUD_AUTH_TOKEN"
    -H "x-goog-user-project: PROJECT_NAME" https://recommender.googleapis.com/v1/projects/my-project/locations/us/recommenders/google.bigquery.table.PartitionClusterRecommender/recommendations

Replace the following:

• GCLOUD_AUTH_TOKEN: the name of a valid gcloud CLI access token
• PROJECT_NAME: the name of the project containing your BigQuery table

The following table describes the important fields from the recommender API response:

Property	Relevant for subtype	Description
recommenderSubtype	Partition or cluster	Indicates the type of recommendation.
content.overview.partitionColumn	Partition	Recommended partitioning column name.
content.overview.partitionTimeUnit	Partition	Recommended partitioning time unit. For example, DAY means the recommendation is to have daily partitions on the recommended column.
content.overview.clusterColumns	Cluster	Recommended clustering column names.

• For more information about other fields in the recommender response, see REST Resource: projects.locations.recommendersrecommendation.
• For more information about using the Recommender API, see Using the API - Recommendations.

To view table insights using the REST API, run the following command:

curl
-H "Authorization: Bearer $GCLOUD_AUTH_TOKEN"
-H "x-goog-user-project: PROJECT_NAME" https://recommender.googleapis.com/v1/projects/my-project/locations/us/insightTypes/google.bigquery.table.StatsInsight/insights

Replace the following:

• GCLOUD_AUTH_TOKEN: the name of a valid gcloud CLI access token
• PROJECT_NAME: the name of the project containing your BigQuery table

The following table describes the important fields from the insights API response:

Property	Relevant for subtype	Description
content.existingPartitionColumn	Cluster	Existing partitioning column, if any
content.tableSizeTb	All	Size of the table in terabytes
content.bytesReadMonthly	All	Monthly bytes read from the table
content.slotMsConsumedMonthly	All	Monthly slot milliseconds consumed by the workload running on the table
content.queryJobsCountMonthly	All	Monthly count of jobs running on the table

• For more information about other fields in the insights response, see REST Resource: projects.locations.insightTypes.insights.
• For more information about using insights, see Using the API - Insights.

Apply cluster recommendations

To apply cluster recommendations, do one of the following:

• Apply clusters directly to the original table
• Apply clusters to a copied table
• Apply clusters in a materialized view

Apply clusters directly to the original table

You can apply cluster recommendations directly to an existing BigQuery table. This method is quicker than applying recommendations to a copied table, but it does not preserve a backup table.

Follow these steps to apply a new clustering specification to unpartitioned or partitioned tables.

1. In the bq tool, update the clustering specification of your table to match the new clustering:

    bq update --clustering_fields=CLUSTER_COLUMN DATASET.ORIGINAL_TABLE 

   Replace the following:

   • CLUSTER_COLUMN: the column you are clustering on—for example, mycolumn
   • DATASET: the name of the dataset containing the table—for example, mydataset
   • ORIGINAL_TABLE: the name of your original table—for example, mytable

   You can also call the tables.update or tables.patch API method to modify the clustering specification.

2. To cluster all rows according to the new clustering specification, run the following UPDATE statement:

   UPDATE DATASET.ORIGINAL_TABLE SET CLUSTER_COLUMN=CLUSTER_COLUMN WHERE true
   

   Note: If a new clustering specification is applied to a table that is in long-term storage, then the table reverts to active storage pricing. For more information, see Storage pricing.

Apply clusters to a copied table

When you apply cluster recommendations to a BigQuery table, you can first copy the original table and then apply the recommendation to the copied table. This method ensures that your original data is preserved if you need to roll back the change to the clustering configuration.

You can use this method to apply cluster recommendations to both unpartitioned and partitioned tables.

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

   Go to BigQuery

2. In the query editor, create an empty table with the same metadata (including the clustering specifications) of the original table by using the LIKE operator:

   CREATE TABLE DATASET.COPIED_TABLE
   LIKE DATASET.ORIGINAL_TABLE
   

   Replace the following:

   • DATASET: the name of the dataset containing the table—for example, mydataset
   • COPIED_TABLE: a name for your copied table—for example, copy_mytable
   • ORIGINAL_TABLE: the name of your original table—for example, mytable

3. In the Google Cloud console, open the Cloud Shell Editor.

   Activate Cloud Shell

4. In the Cloud Shell Editor, update the clustering specification of the copied table to match the recommended clustering by using the bq update command:

    bq update --clustering_fields=CLUSTER_COLUMN DATASET.COPIED_TABLE 

   Replace CLUSTER_COLUMN with the column you are clustering on—for example, mycolumn.

   You can also call the tables.update or tables.patch API method to modify the clustering specification.

5. In the query editor, retrieve the table schema with the partitioning and clustering configuration of the original table, if any partitioning or clustering exists. You can retrieve the schema by viewing the INFORMATION_SCHEMA.TABLES view of the original table:

   SELECT
     ddl
   FROM
     DATASET.INFORMATION_SCHEMA.TABLES
   WHERE
     table_name = 'DATASET.ORIGINAL_TABLE;'
   

   The output is the full data definition language (DDL) statement of ORIGINAL_TABLE, including the PARTITION BY clause. For more information about the arguments in your DDL output, see CREATE TABLE statement.

   The DDL output indicates the type of partitioning in the original table:

   Partitioning type	Output example
   Not partitioned	The PARTITION BY clause is absent.
   Partitioned by table column	PARTITION BY c0
   	PARTITION BY DATE(c0)
   	PARTITION BY DATETIME_TRUNC(c0, MONTH)
   Partitioned by ingestion time	PARTITION BY _PARTITIONDATE
   	PARTITION BY DATETIME_TRUNC(_PARTITIONTIME, MONTH)

6. Ingest data into the copied table. The process that you use is based on the partition type.

   • If the original table is non-partitioned or partitioned by a table column, ingest the data from the original table to the copied table:

     INSERT INTO DATASET.COPIED_TABLE
     SELECT * FROM DATASET.ORIGINAL_TABLE
     

   • If the original table is partitioned by ingestion time, follow these steps:

     1. Retrieve the list of columns to form the data ingestion expression by using the INFORMATION_SCHEMA.COLUMNS view:

        SELECT
        ARRAY_TO_STRING((
        SELECT
          ARRAY(
          SELECT
            column_name
          FROM
            DATASET.INFORMATION_SCHEMA.COLUMNS
          WHERE
            table_name = 'ORIGINAL_TABLE')), ", ")
        

        The output is a comma-separated list of column names.

     2. Ingest the data from the original table to the copied table:

        INSERT DATASET.COPIED_TABLE (COLUMN_NAMES, _PARTITIONTIME)
        SELECT *, _PARTITIONTIME FROM DATASET.ORIGINAL_TABLE
        

        Replace COLUMN_NAMES with the list of columns that was the output in the preceding step, separated by commas—for example, col1, col2, col3.

   You now have a clustered copied table with the same data as the original table. In the next steps, you replace your original table with a newly clustered table.

7. Rename the original table to a backup table:

   ALTER TABLE DATASET.ORIGINAL_TABLE
   RENAME TO DATASET.BACKUP_TABLE
   

   Replace BACKUP_TABLE with a name for your backup table—for example, backup_mytable.

8. Rename the copied table to the original table:

   ALTER TABLE DATASET.COPIED_TABLE
   RENAME TO DATASET.ORIGINAL_TABLE
   

   Your original table is now clustered according to the cluster recommendation.

We recommend that you review the clustered table to ensure that all table functions work as intended. Many table functions are likely tied to the table ID and not the table name, so it is best to review the following table functions before proceeding:

• Access and permissions, such as IAM permissions, row-level access, or column-level access.
• Table artifacts such as table clones, table snapshots, or search indexes.
• The status of any ongoing table processes, such as any materialized views or any jobs that ran when you copied the table.
• The ability to access historical table data using time travel.
• Any metadata associated with the original table—for example, table_option_list or column_option_list. For more information, see Data definition language statements.

If any issues arise, you must manually migrate the affected artifacts to the new table.

After reviewing the clustered table, you can optionally delete the backup table with the following command:

    DROP TABLE DATASET.BACKUP_TABLE
    

Apply clusters in a materialized view

You can create a materialized view of the table to store data from the original table with the recommendation applied. Using materialized views to apply recommendations ensures that the clustered data is kept up to date using automatic refreshes. There are pricing considerations when you query, maintain, and store materialized views. To learn how to create a clustered materialized view, see Clustered materialized views.

Apply partition recommendations

To apply partition recommendations, you must apply it to a copy of the original table. BigQuery does not support the changing of a partitioning scheme of a table in place, such as changing an unpartitioned table to a partitioned table, changing the partitioning scheme of a table, or creating a materialized view with a different partitioning scheme from the base table. You can only change the partitioning of a table on a copy of the table.

Caution: Migrate your legacy SQL workflows to GoogleSQL before applying partition recommendations. For more information, see Limitations.

Apply partition recommendations to a copied table

When you apply partition recommendations to a BigQuery table, you must first copy the original table and then apply the recommendation to the copied table. This approach ensures that your original data is preserved if you need to roll back a partition.

The following procedure uses an example recommendation to partition a table by the partition time unit DAY.

1. Create a copied table using the partition recommendations:

   CREATE TABLE DATASET.COPIED_TABLE
   PARTITION BY DATE_TRUNC(PARTITION_COLUMN, DAY)
   AS SELECT * FROM DATASET.ORIGINAL_TABLE
   

   Replace the following:

   • DATASET: the name of the dataset containing the table—for example, mydataset
   • COPIED_TABLE: a name for your copied table—for example, copy_mytable
   • PARTITION_COLUMN: the column you are partitioning on—for example, mycolumn

   For more information about creating partitioned tables, see Creating partitioned tables.

2. Rename the original table to a backup table:

   ALTER TABLE DATASET.ORIGINAL_TABLE
   RENAME TO DATASET.BACKUP_TABLE
   

   Replace BACKUP_TABLE with a name for your backup table—for example, backup_mytable.

3. Rename the copied table to the original table:

   ALTER TABLE DATASET.COPIED_TABLE
   RENAME TO DATASET.ORIGINAL_TABLE
   

   Your original table is now partitioned according to the partition recommendation.

We recommend that you review the partitioned table to ensure that all table functions work as intended. Many table functions are likely tied to the table ID and not the table name, so it is best to review the following table functions before proceeding:

• Access and permissions, such as IAM permissions, row-level access, or column-level access.
• Table artifacts such as table clones, table snapshots, or search indexes.
• The status of any ongoing table processes, such as any materialized views or any jobs that ran when you copied the table.
• The ability to access historical table data using time travel.
• Any metadata associated with the original table—for example, table_option_list or column_option_list. For more information, see Data definition language statements.
• Ability to use legacy SQL to write query results into partitioned tables. The use of legacy SQL is not fully supported in partitioned tables. One solution is to migrate your legacy SQL workflows into GoogleSQL before applying a partition recommendation.

If any issues arise, you must manually migrate the affected artifacts to the new table.

After reviewing the partitioned table, you can optionally delete the backup table with the following command:

    DROP TABLE DATASET.BACKUP_TABLE
    

Pricing

For details about pricing for this feature, see Gemini in BigQuery pricing overview.

When you apply a recommendation to a table, you can incur the following costs:

• Processing costs. When you apply a recommendation, you execute a data definition language (DDL) or data manipulation language (DML) query to your BigQuery project.
• Storage costs. If you use the method of copying a table, you use extra storage for the copied (or backup) table.

Standard processing and storage charges apply depending on the billing account that's associated with the project. For more information, see BigQuery pricing.

Quotas and limits

For information about quotas and limits for this feature, see Quotas for Gemini in BigQuery.

Troubleshooting

Issue: No recommendations appear for a specific table.

Partition and cluster recommendations might not appear under the following circumstances:

• The table is less than 10GB.
• The table has a high write cost from data manipulation language (DML) operations.
• The table was not read in the past 30 days.
• The estimated monthly savings is too insignificant (less than 1 slot hour of savings).
• The table is already clustered.

Note: Tables that are both unclustered and unpartitioned can receive both cluster and partition recommendations. Tables that are unclustered but partitioned can only receive cluster recommendations. Clustered tables don't receive any recommendations.