Export table data to Cloud Storage (original) (raw)

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This page describes how to export or extract data from BigQuery tables to Cloud Storage.

After you've loaded your data into BigQuery, you can export the data in several formats. BigQuery can export up to 1 GB of data to a single file. If you are exporting more than 1 GB of data, you must export your data to multiple files. When you export your data to multiple files, the size of the files will vary.

You can also export the results of a query by using theEXPORT DATAstatement. You can use EXPORT DATA OPTIONSto specify the format of the exported data.

Finally, you can use a service such as Dataflowto read data from BigQuery instead of exporting it from BigLake. For more information about using Dataflow to read from and write to BigQuery, see BigQuery I/O documentation.

Export limitations

When you export data from BigQuery, note the following:

• You cannot export table data to a local file, to Google Sheets, or to Google Drive. The only supported export location is Cloud Storage. For information on saving query results, see Downloading and saving query results.
• You can export up to 1 GB of table data to a single file. If you are exporting more than 1 GB of data, use a wildcardto export the data into multiple files. When you export data to multiple files, the size of the files will vary. Tolimit the exported file size, you can partition your data and export each partition.
• The generated file size when using the EXPORT DATA statement is not guaranteed.
• The number of files generated by an export job can vary.
• You cannot export nested and repeated data in CSV format. Nested and repeated data are supported for Avro, JSON, and Parquet exports.
• When you export data inJSON format,INT64(integer) data types are encoded as JSON strings to preserve 64-bit precision when the data is read by other systems.
• You cannot export data from multiple tables in a single export job.
• You cannot choose a compression type other than GZIP when you export data using the Google Cloud console.
• When you export a table in JSON format, the symbols <, >, and & are converted by using the unicode notation \uNNNN, where N is a hexadecimal digit. For example, profit&loss becomes profit\u0026loss. This unicode conversion is done to avoid security vulnerabilities.
• The order of exported table data is not guaranteed unless you use theEXPORT DATAstatement and specify an ORDER BY clause in the query_statement.
• BigQuery doesn't support Cloud Storage resource paths that include multiple consecutive slashes after the initial double slash. Cloud Storage object names can contain multiple consecutive slash ("/") characters. However, BigQuery converts multiple consecutive slashes into a single slash. For example, the following resource path, though valid in Cloud Storage, doesn't work in BigQuery: gs://bucket/my//object//name.
• Any new data loaded into BigQuery while an export job is running won't be included in that export job. You must create a new export job to export the new data.

Before you begin

Grant Identity and Access Management (IAM) roles that give users the necessary permissions to perform each task in this document.

Required permissions

To perform the tasks in this document, you need the following permissions.

Permissions to export data from a BigQuery table

To export data from a BigQuery table, you need thebigquery.tables.export IAM permission.

Each of the following predefined IAM roles includes thebigquery.tables.export permission:

• roles/bigquery.dataViewer
• roles/bigquery.dataOwner
• roles/bigquery.dataEditor
• roles/bigquery.admin

Permissions to run an export job

To run an export job, you need the bigquery.jobs.create IAM permission.

Each of the following predefined IAM roles includes the permissions that you need in order to run an export job:

• roles/bigquery.user
• roles/bigquery.jobUser
• roles/bigquery.admin

Permissions to write the data to the Cloud Storage bucket

To write the data to an existing Cloud Storage bucket, you need the following IAM permissions:

• storage.objects.create
• storage.objects.delete

Each of the following predefined IAM roles includes the permissions that you need in order to write the data to an existing Cloud Storage bucket:

• roles/storage.objectAdmin
• roles/storage.admin

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

Export formats and compression types

BigQuery supports the following data formats and compression types for exported data.

Export data

You can export table data by:

• Using the Google Cloud console
• Using the bq extract command in the bq command-line tool
• Submitting an extract job using the API or client libraries

Export table data

To export data from a BigQuery table:

Console

1. Open the BigQuery page in the Google Cloud console.
   Go to the BigQuery page
2. In the Explorer panel, expand your project and dataset, then select the table.
3. In the details panel, click Export and select Export to Cloud Storage.
4. In the Export table to Google Cloud Storage dialog:
   • For Select Google Cloud Storage location, browse for the bucket, folder, or file where you want to export the data.
   • For Export format, choose the format for your exported data: CSV, JSON (Newline Delimited), Avro, or Parquet.
   • For Compression, select a compression format or select None for no compression.
   • Click Save to export the table.

To check on the progress of the job, expand the Job history pane and look for EXTRACT type job.

To export views to Cloud Storage, use EXPORT DATA OPTIONS statement.

SQL

Use theEXPORT DATA statement. The following example exports selected fields from a table named mydataset.table1:

1. In the Google Cloud console, go to the BigQuery page.
   Go to BigQuery
2. In the query editor, enter the following statement:
   EXPORT DATA
   OPTIONS (
   uri = 'gs://bucket/folder/*.csv',
   format = 'CSV',
   overwrite = true,
   header = true,
   field_delimiter = ';')
   AS (
   SELECT field1, field2
   FROM mydataset.table1
   ORDER BY field1
   );
3. Click Run.

For more information about how to run queries, see Run an interactive query.

bq

Use the bq extract command with the --destination_format flag.

(Optional) Supply the --location flag and set the value to yourlocation.

Other optional flags include:

• --compression: The compression type to use for exported files.
• --field_delimiter: The character that indicates the boundary between columns in the output file for CSV exports. Both \t and tab are allowed for tab delimiters.
• --print_header: When specified, print header rows for formats that have headers such as CSV.

bq extract --location=location
--destination_format format
--compression compression_type
--field_delimiter delimiter
--print_header=boolean
project_id:dataset.table
gs://bucket/filename.ext

Where:

• location is the name of your location. The --location flag is optional. For example, if you are using BigQuery in the Tokyo region, you can set the flag's value to asia-northeast1. You can set a default value for the location using the .bigqueryrc file.
• format is the format for the exported data: CSV,NEWLINE_DELIMITED_JSON, AVRO, or PARQUET.
• compression_type is a supported compression type for your data format. See Export formats and compression types.
• delimiter is the character that indicates the boundary between columns in CSV exports. \t and tab are accepted names for tab.
• boolean is true or false. When set to true, header rows are printed to the exported data if the data format supports headers. The default value is true.
• project_id is your project ID.
• dataset is the name of the source dataset.
• table is the table you're exporting. If you use apartition decorator, then you must surround the table path with single quotation marks or escape the $ character.
• bucket is the name of the Cloud Storage bucket to which you're exporting the data. The BigQuery dataset and the Cloud Storage bucket must be in the same location.
• filename.ext is the name and extension of the exported data file. You can export to multiple files using a wildcard.

Examples:

For example, the following command exports mydataset.mytable into a gzip compressed file named myfile.csv. myfile.csv is stored in a Cloud Storage bucket named example-bucket.

bq extract
--compression GZIP
'mydataset.mytable'
gs://example-bucket/myfile.csv

The default destination format is CSV. To export into JSON or Avro, use thedestination_format flag and set it to either NEWLINE_DELIMITED_JSONor AVRO. For example:

bq extract
--destination_format NEWLINE_DELIMITED_JSON
'mydataset.mytable'
gs://example-bucket/myfile.json

The following command exports mydataset.mytable into an Avro file that is compressed using Snappy. The file is named myfile.avro. myfile.avro is exported to a Cloud Storage bucket named example-bucket.

bq extract
--destination_format AVRO
--compression SNAPPY
'mydataset.mytable'
gs://example-bucket/myfile.avro

The following command exports a single partition ofmydataset.my_partitioned_table into a CSV file in Cloud Storage:

bq extract
--destination_format CSV
'mydataset.my_partitioned_table$0'
gs://example-bucket/single_partition.csv

API

To export data, create an extract job and populate the job configuration.

(Optional) Specify your location in the location property in thejobReference section of the job resource.

1. Create an extract job that points to the BigQuery source data and the Cloud Storage destination.
2. Specify the source table by using the sourceTable configuration object that contains the project ID, dataset ID, and table ID.
3. The destination URI(s) property must be fully-qualified, in the formatgs://bucket/filename.ext. Each URI can contain one '*' wildcard character and it must come after the bucket name.
4. Specify the data format by setting theconfiguration.extract.destinationFormatproperty. For example, to export a JSON file, set this property to the value NEWLINE_DELIMITED_JSON.
5. To check the job status, call jobs.get(job_id)with the ID of the job returned by the initial request.
   • If status.state = DONE, the job completed successfully.
   • If the status.errorResult property is present, the request failed, and that object will include information describing what went wrong.
   • If status.errorResult is absent, the job finished successfully, although there might have been some nonfatal errors. Nonfatal errors are listed in the returned job object's status.errors property.

API notes:

• As a best practice, generate a unique ID and pass it asjobReference.jobId when calling jobs.insert to create a job. This approach is more robust to network failure because the client can poll or retry on the known job ID.
• Calling jobs.insert on a given job ID is idempotent; in other words, you can retry as many times as you like on the same job ID, and at most one of those operations will succeed.

C#

Before trying this sample, follow the C# setup instructions in theBigQuery quickstart using client libraries. For more information, see theBigQuery C# API reference documentation.

To authenticate to BigQuery, set up Application Default Credentials. For more information, seeSet up authentication for client libraries.

Go

Before trying this sample, follow the Go setup instructions in theBigQuery quickstart using client libraries. For more information, see theBigQuery Go API reference documentation.

To authenticate to BigQuery, set up Application Default Credentials. For more information, seeSet up authentication for client libraries.

Java

Before trying this sample, follow the Java setup instructions in theBigQuery quickstart using client libraries. For more information, see theBigQuery Java API reference documentation.

To authenticate to BigQuery, set up Application Default Credentials. For more information, seeSet up authentication for client libraries.

Node.js

Before trying this sample, follow the Node.js setup instructions in theBigQuery quickstart using client libraries. For more information, see theBigQuery Node.js API reference documentation.

To authenticate to BigQuery, set up Application Default Credentials. For more information, seeSet up authentication for client libraries.

PHP

Before trying this sample, follow the PHP setup instructions in theBigQuery quickstart using client libraries. For more information, see theBigQuery PHP API reference documentation.

To authenticate to BigQuery, set up Application Default Credentials. For more information, seeSet up authentication for client libraries.

Python

Before trying this sample, follow the Python setup instructions in theBigQuery quickstart using client libraries. For more information, see theBigQuery Python API reference documentation.

To authenticate to BigQuery, set up Application Default Credentials. For more information, seeSet up authentication for client libraries.

Ruby

Before trying this sample, follow the Ruby setup instructions in theBigQuery quickstart using client libraries. For more information, see theBigQuery Ruby API reference documentation.

To authenticate to BigQuery, set up Application Default Credentials. For more information, seeSet up authentication for client libraries.

Export table metadata

To export table metadata from Iceberg tables, use the following SQL statement:

EXPORT TABLE METADATA FROM [[PROJECT_NAME.]DATASET_NAME.]TABLE_NAME;

Replace the following:

• PROJECT_NAME: the name of the project for the table. The value defaults to the project that runs this query.
• DATASET_NAME: the name of the dataset for the table.
• TABLE_NAME: the name of the table.

The exported metadata is located in the STORAGE_URI/metadatafolder, where STORAGE_URI is the table's storage location set in the options.

Avro export details

BigQuery expresses Avro formatted data in the following ways:

• The resulting export files are Avro container files.
• Each BigQuery row is represented as an Avro record. Nested data is represented by nested record objects.
• REQUIRED fields are represented as the corresponding Avro types. For example, a BigQuery INTEGER type maps to an Avro LONG type.
• NULLABLE fields are represented as an Avro union of the corresponding type and "null".
• REPEATED fields are represented as Avro arrays.
• TIMESTAMP data types are represented as timestamp-micros logical type (it annotates an Avro LONG type) by default in both Extract jobs and Export Data SQL. (Caution: you can add use_avro_logical_types=False toExport Data Options to disable the logical type so it uses string type instead on timestamp column, but in Extract Jobs, it always uses the Avro logical type.)
• DATE data types are represented as date logical type (it annotates an AvroINT types) by default in Export Data SQL, but are represented as string type by default in Extract jobs. (Note: you can add use_avro_logical_types=Falseto Export Data Options to disable the logical type, or use the flag--use_avro_logical_types=True to enable the logical type in Extract jobs.)
• TIME data types are represented as timestamp-micro logical type (it annotates an Avro LONG types) by default in Export Data SQL, but are represented as string type by default in Extract jobs. (Note: you can adduse_avro_logical_types=False to Export Data Options to disable the logical type, or use the flag --use_avro_logical_types=True to enable the logical type in Extract jobs.)
• DATETIME data types are represented as Avro STRING types (a string type with custom named logical type datetime) by default in Export Data SQL, but are represented as string type by default in Extract jobs. (Note: you can adduse_avro_logical_types=False to Export Data Options to disable the logical type, or use the flag --use_avro_logical_types=True to enable logical type in Extract jobs.)
• RANGE typesaren't supported in Avro export.

Parameterized NUMERIC(P[, S]) and BIGNUMERIC(P[, S]) data types transfer their precision and scale type parameters to the Avro decimal logical type.

The Avro format can't be used in combination with GZIP compression. To compress Avro data, use the bq command-line tool or the API and specify one of the supported compression types for Avro data: DEFLATE or SNAPPY.

Parquet export details

BigQuery converts GoogleSQL data types to the following Parquet data types:

The Parquet schema represents nested data as a group and repeated records as repeated groups. For more information about using nested and repeated data in BigQuery, seeSpecifying nested and repeated columns.

You can use the following workarounds for DATETIME types:

• Load the file into a staging table. Then use a SQL query to cast the field to a DATETIME and save the result to a new table. For more information, seeChanging a column's data type.
• Provide a schema for the table by using the --schema flag in the load job. Define the datetime column as col:DATETIME.

The GEOGRAPHY logical type is represented withGeoParquet metadata added to the exported file(s).

Exporting data into one or more files

The destinationUris property indicates the one or more locations and filenames where BigQuery should export your files.

BigQuery supports a single wildcard operator (*) in each URI. The wildcard can appear anywhere in the filename component. Using the wildcard operator instructs BigQuery to create multiple sharded files based on the supplied pattern. The wildcard operator is replaced with a number (starting at 0), left-padded to 12 digits. For example, a URI with a wildcard at the end of the filename would create files with000000000000appended to the first file, and 000000000001 appended to the second file, continuing in that pattern.

The following table describes several possible options for the destinationUrisproperty:

Limit the exported file size

When you export more than 1 GB of data in a single export, you must use a wildcard to export the data into multiple files and the size of the files varies. If you need to limit the maximum size of each exported file, one option is to randomly partition your data and then export each partition to a file:

1. Determine the number of partitions you need, which is equal to the total size of your data divided by the chosen exported file size. For example, if you have 8,000 MB of data and you want each exported file to be approximately 20 MB, then you need 400 partitions.
2. Create a new table that is partitioned and clustered by a new randomly generated column called export_id. The following example shows how to create a new processed_table from an existing table called source_tablewhich requires n partitions to achieve the chosen file size:
   CREATE TABLE my_dataset.processed_table
   PARTITION BY RANGE_BUCKET(export_id, GENERATE_ARRAY(0, n, 1))
   CLUSTER BY export_id
   AS (
   SELECT , CAST(FLOOR(nRAND()) AS INT64) AS export_id
   FROM my_dataset.source_table
   );
3. For each integer i between 0 and n-1, run an EXPORT DATA statement on the following query:
   SELECT * EXCEPT(export_id)
   FROM my_dataset.processed_table
   WHERE export_id = i;

Example use case

This example shows how you can export data to Cloud Storage.

Suppose you are streaming data to Cloud Storage from endpoint logs continuously. A daily snapshot is to be exported to Cloud Storage for backup and archival purposes. The best choice is anextract jobsubject to certainquotasandlimitations.

Submit an extract job with theAPIorclient libraries, passing in a unique ID as jobReference.jobId. Extract Jobs are asynchronous.Check the job statususing the unique job ID used to create the job. The job completed successfully if status.status is DONE. If status.errorResult is present, the job failed and needs to be retried.

Batch data processing

Suppose a nightly batch job is used to load data by a fixed deadline. After this load job completes, a table with statistics is materialized from a query as described in the preceding section. Data from this table is retrieved and compiled into a PDF report and sent to a regulator.

Since the amount of data that needs to be read is small, use thetabledata.listAPI to retrieve all rows of the table in JSON dictionary format. If there is more than one page of data, the results have the pageToken property set. To retrieve the next page of results, make another tabledata.list call and include the token value as the pageToken parameter. If the API call fails with a5xx error, retry with exponential backoff. Most 4xx errors cannot be retried. For better decoupling of BigQuery export and report generation, results should be persisted to disk.

Quota policy

For information on export job quotas, see Export jobson the Quotas and limits page.

Usage for export jobs are available in the INFORMATION_SCHEMA. The job entry in the JOBS_BY_* system tables for the export job contains atotal_bytes_processed value that can be used to monitor the aggregate usage to ensure that it stays under 50 TiB per-day. To learn how to query theINFORMATION_SCHEMA.JOBS view to get the total_bytes_processed value, seeINFORMATION_SCHEMA.JOBS schema

View current quota usage

You can view your current usage of query, load, extract, or copy jobs by running an INFORMATION_SCHEMA query to view metadata about the jobs ran over a specified time period. You can compare your current usage against the quota limit to determine your quota usage for a particular type of job. The following example query uses the INFORMATION_SCHEMA.JOBS view to list the number of query, load, extract, and copy jobs by project:

SELECT sum(case when job_type="QUERY" then 1 else 0 end) as QRY_CNT, sum(case when job_type="LOAD" then 1 else 0 end) as LOAD_CNT, sum(case when job_type="EXTRACT" then 1 else 0 end) as EXT_CNT, sum(case when job_type="COPY" then 1 else 0 end) as CPY_CNT FROM region-REGION_NAME.INFORMATION_SCHEMA.JOBS_BY_PROJECT WHERE date(creation_time)= CURRENT_DATE()

You can set up a Cloud Monitoring alert policy that provides notification of the number of bytes exported.

1. In the Google Cloud console, go to the Monitoring page.
   Go to Monitoring
2. In the navigation pane, select Metrics explorer.
3. In the MQL query editor, set up an alert to monitor your exported bytes per day, as seen in the following example:

fetch consumer_quota  
  | filter resource.service == 'bigquery.googleapis.com'  
  | { metric serviceruntime.googleapis.com/quota/rate/net_usage  
      | align delta_gauge(1m)  
      | group_by [resource.project_id, metric.quota_metric, resource.location],  
          sum(value.net_usage)  
    ; metric serviceruntime.googleapis.com/quota/limit  
      | filter metric.limit_name == 'ExtractBytesPerDay'  
      | group_by [resource.project_id, metric.quota_metric, resource.location],  
          sliding(1m), max(val()) }  
  | ratio  
  | every 1m  
  | condition gt(val(), 0.01 '1')  

1. To set up your alert, click Run query.

For more information, see Alerting policies with MQL.

Troubleshooting

To diagnose issues with extract jobs, you can use the Logs Explorerto review the logs for a specific extract job and identify possible errors. The following Logs Explorer filter returns information about your extract jobs:

resource.type="bigquery_resource"
protoPayload.methodName="jobservice.insert"
(protoPayload.serviceData.jobInsertRequest.resource.jobConfiguration.query.query=~"EXPORT" OR
protoPayload.serviceData.jobCompletedEvent.eventName="extract_job_completed" OR
protoPayload.serviceData.jobCompletedEvent.job.jobConfiguration.query.query=~"EXPORT")

Pricing

For information on data export pricing, see the BigQuery pricing page.

Once the data is exported, you are charged for storing the data in Cloud Storage. For more information, see Cloud Storage pricing.

Table security

To control access to tables in BigQuery, seeControl access to resources with IAM.

What's next

• To learn more about the Google Cloud console, seeUsing the Google Cloud console.
• To learn more about the bq command-line tool, seeUsing the bq command-line tool.
• To learn how to create an application using the BigQuery API client libraries, see Client library quickstart.