unable to load csv from GCS bucket to BigQuery table accurately - csv

Question

I am trying to load the airbnb_nyc data set from GCS bucket to BigqueryTable. Link to the dataset.
I am using the following Code:
def parse_file(element):
for line in csv.reader([element],delimiter=','):
return line
class DataIngestion2:
def parse_method2(self, values):
row1 = dict(
zip(('id', 'name', 'host_id', 'host_name', 'neighbourhood_group', 'neighbourhood', 'latitude', 'longitude',
'room_type', 'price', 'minimum_nights', 'number_of_reviews', 'last_review', 'reviews_per_month',
'calculated_host_listings_count', 'availability_365'),
values))
return row1
with beam.Pipeline(options=pipeline_options) as p:
lines= p | 'Read' >> ReadFromText(known_args.input,skip_header_lines=1)\
| 'parse' >> beam.Map(parse_file)
pipeline2 = lines | 'Format to Dict _ original CSV' >> beam.Map(lambda x: data_ingestion2.parse_method2(x))
pipeline2 | 'Load2' >> beam.io.WriteToBigQuery(table_spec, schema=table_schema,
write_disposition=beam.io.BigQueryDisposition.WRITE_TRUNCATE,
create_disposition=beam.io.BigQueryDisposition.CREATE_IF_NEEDED
)
`
But my output on BigQuery Table is wrong.
I am only getting values for the first two columns and the rest of the 14 columns are showing NULL. I am not able to figure out what I am doing wrong. Can Someone Help me find the error in my logic. I basically want to know how to transfer a csv from GCS bucket to BigQuery through DataFlow pipeline.
Thank you,

Answer 1

You can use the ReadFromText method and then create your own transform by extending beam.DoFn. Attached the code below for reference.
https://beam.apache.org/releases/pydoc/2.32.0/apache_beam.io.textio.html#apache_beam.io.textio.ReadFromText
Note that you can use gs:// for GCS in file_pattern.
More details about Pardo and DoFn
https://beam.apache.org/documentation/programming-guide/#pardo
import apache_beam as beam
from apache_beam.io.textio import ReadAllFromText,ReadFromText
from apache_beam.io.gcp.bigquery import WriteToBigQuery
from apache_beam.io.gcp.gcsio import GcsIO
import csv
COLUMN_NAMES = ['id','name','host_id','host_name','neighbourhood_group','neighbourhood','latitude','longitude','room_type','price','minimum_nights','number_of_reviews','last_review','reviews_per_month','calculated_host_listings_count','availability_365']
def files(path='gs:/some/path'):
return list(GcsIO(storage_client='<ur storage client>').list_prefix(path=path).keys())
def transform_csv(element):
rows = []
with open(element,newline='\r\n') as f:
itr = csv.reader(f, delimiter = ',',quotechar= '"')
skip_head = next(itr)
for row in itr:
rows.append(row)
return rows
def to_dict(element):
rows = []
for item in element:
row_dict = {}
zipped = zip(COLUMN_NAMES,item)
for key,val in zipped:
row_dict[key] =val
rows.append(row_dict)
yield rows
with beam.Pipeline() as p:
read =(
p
|'read-file'>> beam.Create(files())
|'transform-dict'>>beam.Map(transform_csv)
|'list-to-dict'>>beam.FlatMap(to_dict )
|'print'>>beam.Map(print)
#|'write-to-bq'>>WriteToBigQuery(schema=COLUMN_NAMES,table='ur table',project='',dataset='')
)
EDITED1 The ReadFromText supports \r\n as newline char.But,this fails to consider the condition where column data itself has \r\n. Updating the code below.
EDITED 2 GcsIo error fixed.
Note - I have used GCSIO for getting the list of files.
Details here
Please Up-vote and mark as answer if this helps.

Answer 2

Let me suggest another approch for this use case. BiqQuery offers special feature for uploading from Google Could Storage (GCS) to Bigquery. You can load data in several formats and CSV is among them.
There is nice tutorial on Google documentation explaining how to do it. You do not have to use Dataflow or apache_beam. Such process is available through BigQuery API itself.
This is working in many languages, but you do not have to use any language as such process can be done from console or via Cloud SDK using bq command. Everything can be found in mentioned tutorial.