Best practices for importing and exporting data

This page provides best practices for importing and exporting data with Cloud SQL. For step-by-step instructions for importing data into Cloud SQL, see Importing Data. For step-by-step instructions for exporting your data, whether it is in Cloud SQL or an instance you manage, see Exporting Data.

Best practices for importing and exporting

The following are best practices to consider when importing and exporting data:

Don't use Cloud Storage Requester Pays buckets

You cannot use a Cloud Storage bucket that has Requester Pays enabled for imports and exports from Cloud SQL.

Use the correct flags when you create a SQL dump file

Compress data to reduce cost

Cloud SQL supports importing and exporting both compressed and uncompressed files. Compression can save significant storage space on Cloud Storage and reduce your storage costs, especially when you are exporting large instances.

When you export a BAK file, use a .gz file extension to compress the data. When you import a file with an extension of .gz, it is decompressed automatically.

Reduce long-running import and export processes

Imports and exports into Cloud SQL using the import functionality (with a Cloud Storage bucket) can take a long time to complete, depending on the size of the database. This can have the following impacts:

  • You cannot stop a long-running Cloud SQL instance operation.
  • You can perform only one import or export operation at a time for each instance.

You can decrease the amount of time it takes to complete each operation by using the Cloud SQL import or export functionality with smaller batches of data.

Verify the imported database

After an import operation is complete, connect to your database and run the appropriate database commands to make sure the contents are correct. For example, connect and list the databases, tables, and specific entries.

Known limitations

Cloud Storage supports a maximum single-object size up five terabytes. If you have databases larger than 5TB, the export operation to Cloud Storage will fail. In that case, you need to break down your export files into smaller segments.

Troubleshooting

Click the links in the table for details:

For this problem... The issue might be... Try this...
Import is taking too long. Too many active connections can interfere with import operations. Close unused connections, or restart the Cloud SQL instance before beginning an import operation.
Import fails. Exported file may contain database users who do not yet exist. Clean up the failed database before retrying the import. Create the database users before doing the import.

Import is taking too long

Import is taking too long, blocking other operations.

The issue might be

Too many active connections can interfere with import operations. Connections consume CPU and memory, limiting the resources available.

Things to try

Close unused operations. Check CPU and memory usage to make sure there are plenty of resources available. The best way to ensure maximum resources for the import operation is to restart the instance before beginning the operation. A restart:

  • Closes all connections.
  • Ends any tasks that may be consuming resources.

Import fails

Import fails when one or more users referenced in the exported SQL dump file does not exist.

The issue might be

Before importing a SQL dump, all the database users who own objects or were granted permissions on objects in the dumped database must exist. If they do not, the restore fails to recreate the objects with the original ownership and/or permissions.

Things to try

Clean up the failed database before retrying the import. Create the database users before importing the SQL dump.

Click the links in the table for details:

For this problem... The issue might be... Try this...
Can't see the operation status. The user interface only shows success or failure. Use these database commands to find out more.
Export is taking too long. Cloud SQL does not support concurrent synchronous operations. Use export offloading. Learn more.
Connection closed during the export operation. Query must produce data within first seven minutes. Test the query manually. Learn more.
Unknown error during export. Possible bandwidth issue. Ensure that both the instance and the Cloud Storage bucket are in the same region.
You want to automate exports. Cloud SQL does not provide a way to automate exports. Build your own pipeline to perform this functionality. Learn more.

Can't see the operation status

You can't see the status of an ongoing operation.

The issue might be

The Google Cloud Console reports only success or failure when done, and is not designed to return warnings.

Things to try

Connect to the database and run SHOW WARNINGS.

Export is taking too long

Export is taking too long, blocking other operations.

The issue might be

Cloud SQL does not support concurrent synchronous operations.

Things to try

Try exporting smaller datasets at a time.

Connection closed during the export operation

Connection closed during the export operation.

The issue might be

The connection to Cloud Storage may be timing out because the query running in the export is not producing any data within the first seven minutes since the export is initiated.

Things to try

Test the query manually by connecting from any client and sending the output of your query to STDOUT with the command below:

COPY (INSERT_YOUR_QUERY_HERE) TO STDOUT WITH ( FORMAT csv, DELIMITER ',', ENCODING 'UTF8', QUOTE '"', ESCAPE '"' ).

This is expected behavior since when the export is initiated, the client is expected to start sending data right away. Keeping the connection with no data sent ends up breaking the connection and eventually resulting in the export failing and leaving the operation in an uncertain state. Also, this is what the error message from gcloud is trying to say with this message:

operation is taking longer than expected.

Unknown error during export

You see the error message Unknown error while trying to export a database to a Cloud Storage bucket.

The issue might be

The transfer might be failing due to a bandwidth issue.

Things to try

The Cloud SQL instance may be located in a different region from the Cloud Storage bucket. Reading and writing data from one continent to another involves a lot of network usage, and can cause intermittent issues like this. Check the regions of your instance and bucket.

Want to automate exports

You want to automate exports.

The issue might be

Cloud SQL does not provide a way to automate exports.

Things to try

You could build your own automated export system using Google Cloud products such as Cloud Scheduler, Pub/Sub, and Cloud Functions.

ERROR_RDBMS system error occurred

You see the error message [ERROR_RDBMS] system error occurred.

The issue might be

  • The user might not have all the Cloud Storage permissions it needs.
  • The database table might not exist.

Things to try

  1. Check that you have at least WRITER permissions on the bucket and READER permissions on the export file. For more information on configuring access control in Cloud Storage, see Create and Manage Access Control Lists.
  2. Ensure the table exists. If the table exists, confirm that you have the correct permissions on the bucket.

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