This document describes how to page through table data and query results using the BigQuery REST API.
Paging through results using the API
All *collection*.list
methods return paginated results
under certain circumstances. The number of results per page is controlled by
the maxResults
property.
Method | Pagination criteria | Default maxResults value |
Maximum maxResults value |
Maximum maxFieldValues value |
---|---|---|---|---|
Tabledata.list |
Returns paginated results if the response size is more than
10 MB1 of data or more than maxResults
rows. |
100,000 | Unlimited | Unlimited |
All other *collection*.list methods |
Returns paginated results if the response is more than
maxResults rows and also below the maximum limits. |
10,000 | Unlimited | 300,000 |
If the result is larger than the byte or field limit, the result is
trimmed to fit the limit. If one row is greater than the byte or field limit,
tabledata.list
can return up to 100 MB of data1,
which is consistent with the maximum row size limit for query results.
1The row size is approximate, as the size is based on the internal representation of row data. The maximum row size limit is enforced during certain stages of query job execution.
jobs.getQueryResult
can return 20 MB of data unless explicitly
requested more through support.
A page is a subset of the total number of rows. If your results are more
than one page of data, the result data will have a pageToken
property. To retrieve the next page of results, make another list
call and include the token value as a URL parameter named pageToken.
The tabledata.list method, which is used to page through table data, uses a row offset value or a page token. See Browsing table data for information.
The following samples demonstrate paging through BigQuery table data.
C#
Before trying this sample, follow the C# setup instructions in the BigQuery Quickstart Using Client Libraries. For more information, see the BigQuery C# API reference documentation.
Java
Before trying this sample, follow the Java setup instructions in the BigQuery Quickstart Using Client Libraries. For more information, see the BigQuery Java API reference documentation.
Go
Before trying this sample, follow the Go setup instructions in the BigQuery Quickstart Using Client Libraries. For more information, see the BigQuery Go API reference documentation.
The Cloud Client Libraries for Go automatically paginates by default, so you do not need to implement pagination yourself, for example:
Node.js
Before trying this sample, follow the Node.js setup instructions in the BigQuery Quickstart Using Client Libraries. For more information, see the BigQuery Node.js API reference documentation.
The Cloud Client Libraries for Node.js automatically paginates by default, so you do not need to implement pagination yourself, for example:
PHP
Before trying this sample, follow the PHP setup instructions in the BigQuery Quickstart Using Client Libraries. For more information, see the BigQuery PHP API reference documentation.
Pagination happens automatically in the Cloud Client Libraries for PHP
using the generator function rows
, which fetches the next page of
results during iteration.
Python
Before trying this sample, follow the Python setup instructions in the BigQuery Quickstart Using Client Libraries. For more information, see the BigQuery Python API reference documentation.
The Cloud Client Libraries for Python automatically paginates by default, so you do not need to implement pagination yourself, for example:
Ruby
Before trying this sample, follow the Ruby setup instructions in the BigQuery Quickstart Using Client Libraries. For more information, see the BigQuery Ruby API reference documentation.
Pagination happens automatically in the Cloud Client Libraries for Ruby
using Table#data
and Data#next
.
Requesting arbitrary pages and avoiding redundant list calls
When you page backwards or jump to arbitrary pages using cached pageToken values, it is possible that the data in your pages might have changed since it was last viewed but there is no clear indication that the data might have changed. To mitigate this, you can use the Etag property.
Every collection.list method (except for Tabledata) returns an Etag property in the result. This property is a hash of the page results that can be used to verify whether the page has changed since last request. When you make a request to BigQuery with an Etag value, BigQuery compares the Etag value to the ETag value returned by the API and responds based on whether the ETag values match. You can use ETags to help avoid redundant list calls in the following ways:
If you only want to return list values if the values have changed:
If you only want to return a page of list values if the values have changed, you can make a list call with a previously-stored ETag using the HTTP "if-none-match" header. If the ETag you provide doesn't match the ETag on the server, BigQuery returns a page of new list values. If the ETags do match, BigQuery returns a HTTP 304 "Not Modified" result and no values. An example of this might be a webpage where users might periodically fill in information that is stored in BigQuery. You can avoid making redundant list calls to BigQuery if there are no changes to your data by using the if-none-match header with ETags.
If you only want to return list values if the values have not changed:
If you only want to return a page of list values if the list values have not changed, you can use the HTTP "if-match" header. BigQuery matches the ETag values and returns the page of results if the results have not changed or returns a 412 "Precondition Failed" result if the page has changed.
Paging through query results
Each query writes to a destination table. If no destination table is provided, the BigQuery API automatically populates the destination table property with a reference to a temporary anonymous table.
API
Read the
jobs.config.query.destinationTable
field to determine the table that query results have been written to.
Call the tabledata.list
to read the query results.
Java
Before trying this sample, follow the Java setup instructions in the BigQuery Quickstart Using Client Libraries. For more information, see the BigQuery Java API reference documentation.
Node.js
Before trying this sample, follow the Node.js setup instructions in the BigQuery Quickstart Using Client Libraries. For more information, see the BigQuery Node.js API reference documentation.
Python
The
QueryJob.result
method returns an iterable of the query results. Alternatively,
- Read the
QueryJob.destination
property. If not configured, this property will be set by the API to a reference to a temporary anonymous table. - Get the table schema with the
Client.get_table
method. - Create an iterable over all rows in the destination table with the
Client.list_rows
method.
Before trying this sample, follow the Python setup instructions in the BigQuery Quickstart Using Client Libraries. For more information, see the BigQuery Python API reference documentation.