Managing Tables¶
Tables exist within datasets. See BigQuery documentation for more information on Tables.
Listing Tables¶
List the tables belonging to a dataset with the
list_tables()
method:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set dataset_id to the ID of the dataset that contains
# the tables you are listing.
# dataset_id = 'your-project.your_dataset'
tables = client.list_tables(dataset_id) # Make an API request.
print("Tables contained in '{}':".format(dataset_id))
for table in tables:
print("{}.{}.{}".format(table.project, table.dataset_id, table.table_id))
Getting a Table¶
Get a table resource with the
get_table()
method:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the model to fetch.
# table_id = 'your-project.your_dataset.your_table'
table = client.get_table(table_id) # Make an API request.
# View table properties
print(
"Got table '{}.{}.{}'.".format(table.project, table.dataset_id, table.table_id)
)
print("Table schema: {}".format(table.schema))
print("Table description: {}".format(table.description))
print("Table has {} rows".format(table.num_rows))
Determine if a table exists with the
get_table()
method:
from google.cloud import bigquery
from google.cloud.exceptions import NotFound
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to determine existence.
# table_id = "your-project.your_dataset.your_table"
try:
client.get_table(table_id) # Make an API request.
print("Table {} already exists.".format(table_id))
except NotFound:
print("Table {} is not found.".format(table_id))
Browse data rows in a table with the
list_rows()
method:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to browse data rows.
# table_id = "your-project.your_dataset.your_table_name"
# Download all rows from a table.
rows_iter = client.list_rows(table_id) # Make an API request.
# Iterate over rows to make the API requests to fetch row data.
rows = list(rows_iter)
print("Downloaded {} rows from table {}".format(len(rows), table_id))
# Download at most 10 rows.
rows_iter = client.list_rows(table_id, max_results=10)
rows = list(rows_iter)
print("Downloaded {} rows from table {}".format(len(rows), table_id))
# Specify selected fields to limit the results to certain columns.
table = client.get_table(table_id) # Make an API request.
fields = table.schema[:2] # First two columns.
rows_iter = client.list_rows(table_id, selected_fields=fields, max_results=10)
rows = list(rows_iter)
print("Selected {} columns from table {}.".format(len(rows_iter.schema), table_id))
print("Downloaded {} rows from table {}".format(len(rows), table_id))
# Print row data in tabular format.
rows = client.list_rows(table, max_results=10)
format_string = "{!s:<16} " * len(rows.schema)
field_names = [field.name for field in rows.schema]
print(format_string.format(*field_names)) # Prints column headers.
for row in rows:
print(format_string.format(*row)) # Prints row data.
Creating a Table¶
Create an empty table with the
create_table()
method:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name"
schema = [
bigquery.SchemaField("full_name", "STRING", mode="REQUIRED"),
bigquery.SchemaField("age", "INTEGER", mode="REQUIRED"),
]
table = bigquery.Table(table_id, schema=schema)
table = client.create_table(table) # Make an API request.
print(
"Created table {}.{}.{}".format(table.project, table.dataset_id, table.table_id)
)
Create a clustered table with the
create_table()
method:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name"
schema = [
bigquery.SchemaField("full_name", "STRING"),
bigquery.SchemaField("city", "STRING"),
bigquery.SchemaField("zipcode", "INTEGER"),
]
table = bigquery.Table(table_id, schema=schema)
table.clustering_fields = ["city", "zipcode"]
table = client.create_table(table) # Make an API request.
print(
"Created clustered table {}.{}.{}".format(
table.project, table.dataset_id, table.table_id
)
)
Create an integer range partitioned table with the
create_table()
method:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name"
schema = [
bigquery.SchemaField("full_name", "STRING"),
bigquery.SchemaField("city", "STRING"),
bigquery.SchemaField("zipcode", "INTEGER"),
]
table = bigquery.Table(table_id, schema=schema)
table.range_partitioning = bigquery.RangePartitioning(
# To use integer range partitioning, select a top-level REQUIRED /
# NULLABLE column with INTEGER / INT64 data type.
field="zipcode",
range_=bigquery.PartitionRange(start=0, end=100000, interval=10),
)
table = client.create_table(table) # Make an API request.
print(
"Created table {}.{}.{}".format(table.project, table.dataset_id, table.table_id)
)
Load table data from a file with the
load_table_from_file()
method:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name"
job_config = bigquery.LoadJobConfig(
source_format=bigquery.SourceFormat.CSV, skip_leading_rows=1, autodetect=True,
)
with open(file_path, "rb") as source_file:
job = client.load_table_from_file(source_file, table_id, job_config=job_config)
job.result() # Waits for the job to complete.
table = client.get_table(table_id) # Make an API request.
print(
"Loaded {} rows and {} columns to {}".format(
table.num_rows, len(table.schema), table_id
)
)
Creating a clustered table from a query result:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the destination table.
# table_id = "your-project.your_dataset.your_table_name"
sql = "SELECT * FROM `bigquery-public-data.samples.shakespeare`"
cluster_fields = ["corpus"]
job_config = bigquery.QueryJobConfig(
clustering_fields=cluster_fields, destination=table_id
)
# Start the query, passing in the extra configuration.
query_job = client.query(sql, job_config=job_config) # Make an API request.
query_job.result() # Wait for the job to complete.
table = client.get_table(table_id) # Make an API request.
if table.clustering_fields == cluster_fields:
print(
"The destination table is written using the cluster_fields configuration."
)
Creating a clustered table when you load data with the
load_table_from_uri()
method:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name"
job_config = bigquery.LoadJobConfig(
skip_leading_rows=1,
source_format=bigquery.SourceFormat.CSV,
schema=[
bigquery.SchemaField("timestamp", bigquery.SqlTypeNames.TIMESTAMP),
bigquery.SchemaField("origin", bigquery.SqlTypeNames.STRING),
bigquery.SchemaField("destination", bigquery.SqlTypeNames.STRING),
bigquery.SchemaField("amount", bigquery.SqlTypeNames.NUMERIC),
],
time_partitioning=bigquery.TimePartitioning(field="timestamp"),
clustering_fields=["origin", "destination"],
)
job = client.load_table_from_uri(
["gs://cloud-samples-data/bigquery/sample-transactions/transactions.csv"],
table_id,
job_config=job_config,
)
job.result() # Waits for the job to complete.
table = client.get_table(table_id) # Make an API request.
print(
"Loaded {} rows and {} columns to {}".format(
table.num_rows, len(table.schema), table_id
)
)
Load a CSV file from Cloud Storage with the
load_table_from_uri()
method:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name"
job_config = bigquery.LoadJobConfig(
schema=[
bigquery.SchemaField("name", "STRING"),
bigquery.SchemaField("post_abbr", "STRING"),
],
skip_leading_rows=1,
# The source format defaults to CSV, so the line below is optional.
source_format=bigquery.SourceFormat.CSV,
)
uri = "gs://cloud-samples-data/bigquery/us-states/us-states.csv"
load_job = client.load_table_from_uri(
uri, table_id, job_config=job_config
) # Make an API request.
load_job.result() # Waits for the job to complete.
destination_table = client.get_table(table_id) # Make an API request.
print("Loaded {} rows.".format(destination_table.num_rows))
See also: Loading CSV data from Cloud Storage.
Load a JSON file from Cloud Storage:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name"
job_config = bigquery.LoadJobConfig(
schema=[
bigquery.SchemaField("name", "STRING"),
bigquery.SchemaField("post_abbr", "STRING"),
],
source_format=bigquery.SourceFormat.NEWLINE_DELIMITED_JSON,
)
uri = "gs://cloud-samples-data/bigquery/us-states/us-states.json"
load_job = client.load_table_from_uri(
uri,
table_id,
location="US", # Must match the destination dataset location.
job_config=job_config,
) # Make an API request.
load_job.result() # Waits for the job to complete.
destination_table = client.get_table(table_id)
print("Loaded {} rows.".format(destination_table.num_rows))
See also: Loading JSON data from Cloud Storage.
Load a Parquet file from Cloud Storage:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name"
job_config = bigquery.LoadJobConfig(source_format=bigquery.SourceFormat.PARQUET,)
uri = "gs://cloud-samples-data/bigquery/us-states/us-states.parquet"
load_job = client.load_table_from_uri(
uri, table_id, job_config=job_config
) # Make an API request.
load_job.result() # Waits for the job to complete.
destination_table = client.get_table(table_id)
print("Loaded {} rows.".format(destination_table.num_rows))
See also: Loading Parquet data from Cloud Storage.
Load an Avro file from Cloud Storage:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name
job_config = bigquery.LoadJobConfig(source_format=bigquery.SourceFormat.AVRO)
uri = "gs://cloud-samples-data/bigquery/us-states/us-states.avro"
load_job = client.load_table_from_uri(
uri, table_id, job_config=job_config
) # Make an API request.
load_job.result() # Waits for the job to complete.
destination_table = client.get_table(table_id)
print("Loaded {} rows.".format(destination_table.num_rows))
See also: Loading Avro data from Cloud Storage.
Load an ORC file from Cloud Storage:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name
job_config = bigquery.LoadJobConfig(source_format=bigquery.SourceFormat.ORC)
uri = "gs://cloud-samples-data/bigquery/us-states/us-states.orc"
load_job = client.load_table_from_uri(
uri, table_id, job_config=job_config
) # Make an API request.
load_job.result() # Waits for the job to complete.
destination_table = client.get_table(table_id)
print("Loaded {} rows.".format(destination_table.num_rows))
See also: Loading ORC data from Cloud Storage.
Load a CSV file from Cloud Storage and auto-detect schema:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name
# Set the encryption key to use for the destination.
# TODO: Replace this key with a key you have created in KMS.
# kms_key_name = "projects/{}/locations/{}/keyRings/{}/cryptoKeys/{}".format(
# "cloud-samples-tests", "us", "test", "test"
# )
job_config = bigquery.LoadJobConfig(
autodetect=True,
skip_leading_rows=1,
# The source format defaults to CSV, so the line below is optional.
source_format=bigquery.SourceFormat.CSV,
)
uri = "gs://cloud-samples-data/bigquery/us-states/us-states.csv"
load_job = client.load_table_from_uri(
uri, table_id, job_config=job_config
) # Make an API request.
load_job.result() # Waits for the job to complete.
destination_table = client.get_table(table_id)
print("Loaded {} rows.".format(destination_table.num_rows))
Load a JSON file from Cloud Storage and auto-detect schema:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name
# Set the encryption key to use for the destination.
# TODO: Replace this key with a key you have created in KMS.
# kms_key_name = "projects/{}/locations/{}/keyRings/{}/cryptoKeys/{}".format(
# "cloud-samples-tests", "us", "test", "test"
# )
job_config = bigquery.LoadJobConfig(
autodetect=True, source_format=bigquery.SourceFormat.NEWLINE_DELIMITED_JSON
)
uri = "gs://cloud-samples-data/bigquery/us-states/us-states.json"
load_job = client.load_table_from_uri(
uri, table_id, job_config=job_config
) # Make an API request.
load_job.result() # Waits for the job to complete.
destination_table = client.get_table(table_id)
print("Loaded {} rows.".format(destination_table.num_rows))
Updating a Table¶
Update a property in a table’s metadata with the
update_table()
method:
# from google.cloud import bigquery
# client = bigquery.Client()
# project = client.project
# dataset_ref = bigquery.DatasetReference(project, dataset_id)
# table_ref = dataset_ref.table('my_table')
# table = client.get_table(table_ref) # API request
assert table.description == "Original description."
table.description = "Updated description."
table = client.update_table(table, ["description"]) # API request
assert table.description == "Updated description."
Insert rows into a table’s data with the
insert_rows()
method:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of table to append to.
# table_id = "your-project.your_dataset.your_table"
rows_to_insert = [
{u"full_name": u"Phred Phlyntstone", u"age": 32},
{u"full_name": u"Wylma Phlyntstone", u"age": 29},
]
errors = client.insert_rows_json(table_id, rows_to_insert) # Make an API request.
if errors == []:
print("New rows have been added.")
else:
print("Encountered errors while inserting rows: {}".format(errors))
Insert rows into a table’s data with the
insert_rows()
method, achieving
higher write limit:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of table to append to.
# table_id = "your-project.your_dataset.your_table"
rows_to_insert = [
{u"full_name": u"Phred Phlyntstone", u"age": 32},
{u"full_name": u"Wylma Phlyntstone", u"age": 29},
]
errors = client.insert_rows_json(
table_id, rows_to_insert, row_ids=[None] * len(rows_to_insert)
) # Make an API request.
if errors == []:
print("New rows have been added.")
else:
print("Encountered errors while inserting rows: {}".format(errors))
Mind that inserting data with None
row insert IDs can come at the expense of
more duplicate inserts. See also:
Streaming inserts.
Add an empty column to the existing table with the
update_table()
method:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table
# to add an empty column.
# table_id = "your-project.your_dataset.your_table_name"
table = client.get_table(table_id) # Make an API request.
original_schema = table.schema
new_schema = original_schema[:] # Creates a copy of the schema.
new_schema.append(bigquery.SchemaField("phone", "STRING"))
table.schema = new_schema
table = client.update_table(table, ["schema"]) # Make an API request.
if len(table.schema) == len(original_schema) + 1 == len(new_schema):
print("A new column has been added.")
else:
print("The column has not been added.")
Copying a Table¶
Copy a table with the
copy_table()
method:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set source_table_id to the ID of the original table.
# source_table_id = "your-project.source_dataset.source_table"
# TODO(developer): Set destination_table_id to the ID of the destination table.
# destination_table_id = "your-project.destination_dataset.destination_table"
job = client.copy_table(source_table_id, destination_table_id)
job.result() # Wait for the job to complete.
print("A copy of the table created.")
Copy table data to Google Cloud Storage with the
extract_table()
method:
# from google.cloud import bigquery
# client = bigquery.Client()
# bucket_name = 'my-bucket'
project = "bigquery-public-data"
dataset_id = "samples"
table_id = "shakespeare"
destination_uri = "gs://{}/{}".format(bucket_name, "shakespeare.csv")
dataset_ref = bigquery.DatasetReference(project, dataset_id)
table_ref = dataset_ref.table(table_id)
extract_job = client.extract_table(
table_ref,
destination_uri,
# Location must match that of the source table.
location="US",
) # API request
extract_job.result() # Waits for job to complete.
print(
"Exported {}:{}.{} to {}".format(project, dataset_id, table_id, destination_uri)
)
Deleting a Table¶
Delete a table with the
delete_table()
method:
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to fetch.
# table_id = 'your-project.your_dataset.your_table'
# If the table does not exist, delete_table raises
# google.api_core.exceptions.NotFound unless not_found_ok is True.
client.delete_table(table_id, not_found_ok=True) # Make an API request.
print("Deleted table '{}'.".format(table_id))
Restoring a Deleted Table¶
Restore a deleted table from a snapshot by using the
copy_table()
method:
import time
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Choose a table to recover.
# table_id = "your-project.your_dataset.your_table"
# TODO(developer): Choose a new table ID for the recovered table data.
# recovery_table_id = "your-project.your_dataset.your_table_recovered"
# TODO(developer): Choose an appropriate snapshot point as epoch
# milliseconds. For this example, we choose the current time as we're about
# to delete the table immediately afterwards.
snapshot_epoch = int(time.time() * 1000)
# [START_EXCLUDE]
# Due to very short lifecycle of the table, ensure we're not picking a time
# prior to the table creation due to time drift between backend and client.
table = client.get_table(table_id)
created_epoch = datetime_helpers.to_milliseconds(table.created)
if created_epoch > snapshot_epoch:
snapshot_epoch = created_epoch
# [END_EXCLUDE]
# "Accidentally" delete the table.
client.delete_table(table_id) # Make an API request.
# Construct the restore-from table ID using a snapshot decorator.
snapshot_table_id = "{}@{}".format(table_id, snapshot_epoch)
# Construct and run a copy job.
job = client.copy_table(
snapshot_table_id,
recovered_table_id,
# Must match the source and destination tables location.
location="US",
) # Make an API request.
job.result() # Wait for the job to complete.
print(
"Copied data from deleted table {} to {}".format(table_id, recovered_table_id)
)
Overwrite a Table¶
Replace the table data with an Avro file from Cloud Storage:
import six
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name
job_config = bigquery.LoadJobConfig(
schema=[
bigquery.SchemaField("name", "STRING"),
bigquery.SchemaField("post_abbr", "STRING"),
],
)
body = six.BytesIO(b"Washington,WA")
client.load_table_from_file(body, table_id, job_config=job_config).result()
previous_rows = client.get_table(table_id).num_rows
assert previous_rows > 0
job_config = bigquery.LoadJobConfig(
write_disposition=bigquery.WriteDisposition.WRITE_TRUNCATE,
source_format=bigquery.SourceFormat.AVRO,
)
uri = "gs://cloud-samples-data/bigquery/us-states/us-states.avro"
load_job = client.load_table_from_uri(
uri, table_id, job_config=job_config
) # Make an API request.
load_job.result() # Waits for the job to complete.
destination_table = client.get_table(table_id)
print("Loaded {} rows.".format(destination_table.num_rows))
Replace the table data with a CSV file from Cloud Storage:
import six
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name
job_config = bigquery.LoadJobConfig(
schema=[
bigquery.SchemaField("name", "STRING"),
bigquery.SchemaField("post_abbr", "STRING"),
],
)
body = six.BytesIO(b"Washington,WA")
client.load_table_from_file(body, table_id, job_config=job_config).result()
previous_rows = client.get_table(table_id).num_rows
assert previous_rows > 0
job_config = bigquery.LoadJobConfig(
write_disposition=bigquery.WriteDisposition.WRITE_TRUNCATE,
source_format=bigquery.SourceFormat.CSV,
skip_leading_rows=1,
)
uri = "gs://cloud-samples-data/bigquery/us-states/us-states.csv"
load_job = client.load_table_from_uri(
uri, table_id, job_config=job_config
) # Make an API request.
load_job.result() # Waits for the job to complete.
destination_table = client.get_table(table_id)
print("Loaded {} rows.".format(destination_table.num_rows))
Replace the table data with a JSON file from Cloud Storage:
import six
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name
job_config = bigquery.LoadJobConfig(
schema=[
bigquery.SchemaField("name", "STRING"),
bigquery.SchemaField("post_abbr", "STRING"),
],
)
body = six.BytesIO(b"Washington,WA")
client.load_table_from_file(body, table_id, job_config=job_config).result()
previous_rows = client.get_table(table_id).num_rows
assert previous_rows > 0
job_config = bigquery.LoadJobConfig(
write_disposition=bigquery.WriteDisposition.WRITE_TRUNCATE,
source_format=bigquery.SourceFormat.NEWLINE_DELIMITED_JSON,
)
uri = "gs://cloud-samples-data/bigquery/us-states/us-states.json"
load_job = client.load_table_from_uri(
uri, table_id, job_config=job_config
) # Make an API request.
load_job.result() # Waits for the job to complete.
destination_table = client.get_table(table_id)
print("Loaded {} rows.".format(destination_table.num_rows))
Replace the table data with an ORC file from Cloud Storage:
import six
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name
job_config = bigquery.LoadJobConfig(
schema=[
bigquery.SchemaField("name", "STRING"),
bigquery.SchemaField("post_abbr", "STRING"),
],
)
body = six.BytesIO(b"Washington,WA")
client.load_table_from_file(body, table_id, job_config=job_config).result()
previous_rows = client.get_table(table_id).num_rows
assert previous_rows > 0
job_config = bigquery.LoadJobConfig(
write_disposition=bigquery.WriteDisposition.WRITE_TRUNCATE,
source_format=bigquery.SourceFormat.ORC,
)
uri = "gs://cloud-samples-data/bigquery/us-states/us-states.orc"
load_job = client.load_table_from_uri(
uri, table_id, job_config=job_config
) # Make an API request.
load_job.result() # Waits for the job to complete.
destination_table = client.get_table(table_id)
print("Loaded {} rows.".format(destination_table.num_rows))
Replace the table data with a Parquet file from Cloud Storage:
import six
from google.cloud import bigquery
# Construct a BigQuery client object.
client = bigquery.Client()
# TODO(developer): Set table_id to the ID of the table to create.
# table_id = "your-project.your_dataset.your_table_name
job_config = bigquery.LoadJobConfig(
schema=[
bigquery.SchemaField("name", "STRING"),
bigquery.SchemaField("post_abbr", "STRING"),
],
)
body = six.BytesIO(b"Washington,WA")
client.load_table_from_file(body, table_id, job_config=job_config).result()
previous_rows = client.get_table(table_id).num_rows
assert previous_rows > 0
job_config = bigquery.LoadJobConfig(
write_disposition=bigquery.WriteDisposition.WRITE_TRUNCATE,
source_format=bigquery.SourceFormat.PARQUET,
)
uri = "gs://cloud-samples-data/bigquery/us-states/us-states.parquet"
load_job = client.load_table_from_uri(
uri, table_id, job_config=job_config
) # Make an API request.
load_job.result() # Waits for the job to complete.
destination_table = client.get_table(table_id)
print("Loaded {} rows.".format(destination_table.num_rows))