How to best handle data stored in different locations in Google BigQuery?

Question

My current workflow in BigQuery is as follows:

(1) query data in a public repository (stored in the US), (2) write it to a table in my repository, (3) export a csv

Answer 1

One way to copy a BigQuery dataset from one region to another is to take advantage of the Storage Data Transfer Service. It doesn't get around the fact that you still have to pay for bucket-to-bucket network traffic, but might save you some CPU time on copying data to a server in the EU.

The flow would be to:

1. Extract all the BigQuery tables into a bucket in the same region as the tables. (Recommend Avro format for best fidelity in data types and fastest loading speed.)
2. Run a storage transfer job to copy the extracted files from the starting location bucket to a bucket in the destination location.
3. Load all the files into a BigQuery dataset located in the destination location.

Python example:

# Copyright 2018 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import datetime
import sys
import time

import googleapiclient.discovery
from google.cloud import bigquery
import json
import pytz


PROJECT_ID = 'swast-scratch'  # TODO: set this to your project name
FROM_LOCATION = 'US'  # TODO: set this to the BigQuery location
FROM_DATASET = 'workflow_test_us'  # TODO: set to BQ dataset name
FROM_BUCKET = 'swast-scratch-us'  # TODO: set to bucket name in same location
TO_LOCATION = 'EU'  # TODO: set this to the destination BigQuery location
TO_DATASET = 'workflow_test_eu'  # TODO: set to destination dataset name
TO_BUCKET = 'swast-scratch-eu'  # TODO: set to bucket name in destination loc

# Construct API clients.
bq_client = bigquery.Client(project=PROJECT_ID)
transfer_client = googleapiclient.discovery.build('storagetransfer', 'v1')


def extract_tables():
    # Extract all tables in a dataset to a Cloud Storage bucket.
    print('Extracting {}:{} to bucket {}'.format(
        PROJECT_ID, FROM_DATASET, FROM_BUCKET))

    tables = list(bq_client.list_tables(bq_client.dataset(FROM_DATASET)))
    extract_jobs = []
    for table in tables:
        job_config = bigquery.ExtractJobConfig()
        job_config.destination_format = bigquery.DestinationFormat.AVRO
        extract_job = bq_client.extract_table(
            table.reference,
            ['gs://{}/{}.avro'.format(FROM_BUCKET, table.table_id)],
            location=FROM_LOCATION,  # Available in 0.32.0 library.
            job_config=job_config)  # Starts the extract job.
        extract_jobs.append(extract_job)

    for job in extract_jobs:
        job.result()

    return tables


def transfer_buckets():
    # Transfer files from one region to another using storage transfer service.
    print('Transferring bucket {} to {}'.format(FROM_BUCKET, TO_BUCKET))
    now = datetime.datetime.now(pytz.utc)
    transfer_job = {
        'description': '{}-{}-{}_once'.format(
            PROJECT_ID, FROM_BUCKET, TO_BUCKET),
        'status': 'ENABLED',
        'projectId': PROJECT_ID,
        'transferSpec': {
            'transferOptions': {
                'overwriteObjectsAlreadyExistingInSink': True,
            },
            'gcsDataSource': {
                'bucketName': FROM_BUCKET,
            },
            'gcsDataSink': {
                'bucketName': TO_BUCKET,
            },
        },
        # Set start and end date to today (UTC) without a time part to start
        # the job immediately.
        'schedule': {
            'scheduleStartDate': {
                'year': now.year,
                'month': now.month,
                'day': now.day,
            },
            'scheduleEndDate': {
                'year': now.year,
                'month': now.month,
                'day': now.day,
            },
        },
    }
    transfer_job = transfer_client.transferJobs().create(
        body=transfer_job).execute()
    print('Returned transferJob: {}'.format(
        json.dumps(transfer_job, indent=4)))

    # Find the operation created for the job.
    job_filter = {
        'project_id': PROJECT_ID,
        'job_names': [transfer_job['name']],
    }

    # Wait until the operation has started.
    response = {}
    while ('operations' not in response) or (not response['operations']):
        time.sleep(1)
        response = transfer_client.transferOperations().list(
            name='transferOperations', filter=json.dumps(job_filter)).execute()

    operation = response['operations'][0]
    print('Returned transferOperation: {}'.format(
        json.dumps(operation, indent=4)))

    # Wait for the transfer to complete.
    print('Waiting ', end='')
    while operation['metadata']['status'] == 'IN_PROGRESS':
        print('.', end='')
        sys.stdout.flush()
        time.sleep(5)
        operation = transfer_client.transferOperations().get(
            name=operation['name']).execute()
    print()

    print('Finished transferOperation: {}'.format(
        json.dumps(operation, indent=4)))


def load_tables(tables):
    # Load all tables into the new dataset.
    print('Loading tables from bucket {} to {}:{}'.format(
        TO_BUCKET, PROJECT_ID, TO_DATASET))

    load_jobs = []
    for table in tables:
        dest_table = bq_client.dataset(TO_DATASET).table(table.table_id)
        job_config = bigquery.LoadJobConfig()
        job_config.source_format = bigquery.SourceFormat.AVRO
        load_job = bq_client.load_table_from_uri(
            ['gs://{}/{}.avro'.format(TO_BUCKET, table.table_id)],
            dest_table,
            location=TO_LOCATION,  # Available in 0.32.0 library.
            job_config=job_config)  # Starts the load job.
        load_jobs.append(load_job)

    for job in load_jobs:
        job.result()


# Actually run the script.
tables = extract_tables()
transfer_buckets()
load_tables(tables)

The preceding sample uses google-cloud-bigquery library for BigQuery API and google-api-python-client for Storage Data Transfer API.

Note that this sample does not account for partitioned tables.