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"""Base operator for SQL to GCS operators."""
import abc
import json
from tempfile import NamedTemporaryFile
from typing import TYPE_CHECKING, Dict, Optional, Sequence, Union
import pyarrow as pa
import pyarrow.parquet as pq
import unicodecsv as csv
from airflow.models import BaseOperator
from airflow.providers.google.cloud.hooks.gcs import GCSHook
if TYPE_CHECKING:
from airflow.utils.context import Context
[docs]class BaseSQLToGCSOperator(BaseOperator):
"""
Copy data from SQL to Google Cloud Storage in JSON or CSV format.
:param sql: The SQL to execute.
:param bucket: The bucket to upload to.
:param filename: The filename to use as the object name when uploading
to Google Cloud Storage. A ``{}`` should be specified in the filename
to allow the operator to inject file numbers in cases where the
file is split due to size.
:param schema_filename: If set, the filename to use as the object name
when uploading a .json file containing the BigQuery schema fields
for the table that was dumped from the database.
:param approx_max_file_size_bytes: This operator supports the ability
to split large table dumps into multiple files (see notes in the
filename param docs above). This param allows developers to specify the
file size of the splits. Check https://cloud.google.com/storage/quotas
to see the maximum allowed file size for a single object.
:param export_format: Desired format of files to be exported.
:param field_delimiter: The delimiter to be used for CSV files.
:param null_marker: The null marker to be used for CSV files.
:param gzip: Option to compress file for upload (does not apply to schemas).
:param schema: The schema to use, if any. Should be a list of dict or
a str. Pass a string if using Jinja template, otherwise, pass a list of
dict. Examples could be seen: https://cloud.google.com/bigquery/docs
/schemas#specifying_a_json_schema_file
:param gcp_conn_id: (Optional) The connection ID used to connect to Google Cloud.
:param delegate_to: The account to impersonate using domain-wide delegation of authority,
if any. For this to work, the service account making the request must have
domain-wide delegation enabled.
:param parameters: a parameters dict that is substituted at query runtime.
:param impersonation_chain: Optional service account to impersonate using short-term
credentials, or chained list of accounts required to get the access_token
of the last account in the list, which will be impersonated in the request.
If set as a string, the account must grant the originating account
the Service Account Token Creator IAM role.
If set as a sequence, the identities from the list must grant
Service Account Token Creator IAM role to the directly preceding identity, with first
account from the list granting this role to the originating account (templated).
"""
[docs] template_fields: Sequence[str] = (
'sql',
'bucket',
'filename',
'schema_filename',
'schema',
'parameters',
'impersonation_chain',
)
[docs] template_ext: Sequence[str] = ('.sql',)
[docs] template_fields_renderers = {'sql': 'sql'}
def __init__(
self,
*,
sql: str,
bucket: str,
filename: str,
schema_filename: Optional[str] = None,
approx_max_file_size_bytes: int = 1900000000,
export_format: str = 'json',
field_delimiter: str = ',',
null_marker: Optional[str] = None,
gzip: bool = False,
schema: Optional[Union[str, list]] = None,
parameters: Optional[dict] = None,
gcp_conn_id: str = 'google_cloud_default',
delegate_to: Optional[str] = None,
impersonation_chain: Optional[Union[str, Sequence[str]]] = None,
**kwargs,
) -> None:
super().__init__(**kwargs)
self.sql = sql
self.bucket = bucket
self.filename = filename
self.schema_filename = schema_filename
self.approx_max_file_size_bytes = approx_max_file_size_bytes
self.export_format = export_format.lower()
self.field_delimiter = field_delimiter
self.null_marker = null_marker
self.gzip = gzip
self.schema = schema
self.parameters = parameters
self.gcp_conn_id = gcp_conn_id
self.delegate_to = delegate_to
self.impersonation_chain = impersonation_chain
[docs] def execute(self, context: 'Context'):
self.log.info("Executing query")
cursor = self.query()
# If a schema is set, create a BQ schema JSON file.
if self.schema_filename:
self.log.info('Writing local schema file')
schema_file = self._write_local_schema_file(cursor)
# Flush file before uploading
schema_file['file_handle'].flush()
self.log.info('Uploading schema file to GCS.')
self._upload_to_gcs(schema_file)
schema_file['file_handle'].close()
counter = 0
self.log.info('Writing local data files')
for file_to_upload in self._write_local_data_files(cursor):
# Flush file before uploading
file_to_upload['file_handle'].flush()
self.log.info('Uploading chunk file #%d to GCS.', counter)
self._upload_to_gcs(file_to_upload)
self.log.info('Removing local file')
file_to_upload['file_handle'].close()
counter += 1
[docs] def convert_types(self, schema, col_type_dict, row, stringify_dict=False) -> list:
"""Convert values from DBAPI to output-friendly formats."""
return [
self.convert_type(value, col_type_dict.get(name), stringify_dict=stringify_dict)
for name, value in zip(schema, row)
]
def _write_local_data_files(self, cursor):
"""
Takes a cursor, and writes results to a local file.
:return: A dictionary where keys are filenames to be used as object
names in GCS, and values are file handles to local files that
contain the data for the GCS objects.
"""
schema = list(map(lambda schema_tuple: schema_tuple[0], cursor.description))
col_type_dict = self._get_col_type_dict()
file_no = 0
tmp_file_handle = NamedTemporaryFile(delete=True)
if self.export_format == 'csv':
file_mime_type = 'text/csv'
elif self.export_format == 'parquet':
file_mime_type = 'application/octet-stream'
else:
file_mime_type = 'application/json'
file_to_upload = {
'file_name': self.filename.format(file_no),
'file_handle': tmp_file_handle,
'file_mime_type': file_mime_type,
}
if self.export_format == 'csv':
csv_writer = self._configure_csv_file(tmp_file_handle, schema)
if self.export_format == 'parquet':
parquet_schema = self._convert_parquet_schema(cursor)
parquet_writer = self._configure_parquet_file(tmp_file_handle, parquet_schema)
for row in cursor:
if self.export_format == 'csv':
row = self.convert_types(schema, col_type_dict, row)
if self.null_marker is not None:
row = [value if value is not None else self.null_marker for value in row]
csv_writer.writerow(row)
elif self.export_format == 'parquet':
row = self.convert_types(schema, col_type_dict, row)
if self.null_marker is not None:
row = [value if value is not None else self.null_marker for value in row]
row_pydic = {col: [value] for col, value in zip(schema, row)}
tbl = pa.Table.from_pydict(row_pydic, parquet_schema)
parquet_writer.write_table(tbl)
else:
row = self.convert_types(schema, col_type_dict, row, stringify_dict=False)
row_dict = dict(zip(schema, row))
tmp_file_handle.write(
json.dumps(row_dict, sort_keys=True, ensure_ascii=False).encode("utf-8")
)
# Append newline to make dumps BigQuery compatible.
tmp_file_handle.write(b'\n')
# Stop if the file exceeds the file size limit.
if tmp_file_handle.tell() >= self.approx_max_file_size_bytes:
file_no += 1
if self.export_format == 'parquet':
parquet_writer.close()
yield file_to_upload
tmp_file_handle = NamedTemporaryFile(delete=True)
file_to_upload = {
'file_name': self.filename.format(file_no),
'file_handle': tmp_file_handle,
'file_mime_type': file_mime_type,
}
if self.export_format == 'csv':
csv_writer = self._configure_csv_file(tmp_file_handle, schema)
if self.export_format == 'parquet':
parquet_writer = self._configure_parquet_file(tmp_file_handle, parquet_schema)
if self.export_format == 'parquet':
parquet_writer.close()
yield file_to_upload
def _configure_csv_file(self, file_handle, schema):
"""Configure a csv writer with the file_handle and write schema
as headers for the new file.
"""
csv_writer = csv.writer(file_handle, encoding='utf-8', delimiter=self.field_delimiter)
csv_writer.writerow(schema)
return csv_writer
def _configure_parquet_file(self, file_handle, parquet_schema):
parquet_writer = pq.ParquetWriter(file_handle.name, parquet_schema)
return parquet_writer
def _convert_parquet_schema(self, cursor):
type_map = {
'INTEGER': pa.int64(),
'FLOAT': pa.float64(),
'NUMERIC': pa.float64(),
'BIGNUMERIC': pa.float64(),
'BOOL': pa.bool_(),
'STRING': pa.string(),
'BYTES': pa.binary(),
'DATE': pa.date32(),
'DATETIME': pa.date64(),
'TIMESTAMP': pa.timestamp('s'),
}
columns = [field[0] for field in cursor.description]
bq_fields = [self.field_to_bigquery(field) for field in cursor.description]
bq_types = [bq_field.get('type') if bq_field is not None else None for bq_field in bq_fields]
pq_types = [type_map.get(bq_type, pa.string()) for bq_type in bq_types]
parquet_schema = pa.schema(zip(columns, pq_types))
return parquet_schema
@abc.abstractmethod
[docs] def query(self):
"""Execute DBAPI query."""
@abc.abstractmethod
[docs] def field_to_bigquery(self, field) -> Dict[str, str]:
"""Convert a DBAPI field to BigQuery schema format."""
@abc.abstractmethod
[docs] def convert_type(self, value, schema_type, **kwargs):
"""Convert a value from DBAPI to output-friendly formats."""
def _get_col_type_dict(self):
"""Return a dict of column name and column type based on self.schema if not None."""
schema = []
if isinstance(self.schema, str):
schema = json.loads(self.schema)
elif isinstance(self.schema, list):
schema = self.schema
elif self.schema is not None:
self.log.warning('Using default schema due to unexpected type. Should be a string or list.')
col_type_dict = {}
try:
col_type_dict = {col['name']: col['type'] for col in schema}
except KeyError:
self.log.warning(
'Using default schema due to missing name or type. Please '
'refer to: https://cloud.google.com/bigquery/docs/schemas'
'#specifying_a_json_schema_file'
)
return col_type_dict
def _write_local_schema_file(self, cursor):
"""
Takes a cursor, and writes the BigQuery schema for the results to a
local file system. Schema for database will be read from cursor if
not specified.
:return: A dictionary where key is a filename to be used as an object
name in GCS, and values are file handles to local files that
contains the BigQuery schema fields in .json format.
"""
if self.schema:
self.log.info("Using user schema")
schema = self.schema
else:
self.log.info("Starts generating schema")
schema = [self.field_to_bigquery(field) for field in cursor.description]
if isinstance(schema, list):
schema = json.dumps(schema, sort_keys=True)
self.log.info('Using schema for %s', self.schema_filename)
self.log.debug("Current schema: %s", schema)
tmp_schema_file_handle = NamedTemporaryFile(delete=True)
tmp_schema_file_handle.write(schema.encode('utf-8'))
schema_file_to_upload = {
'file_name': self.schema_filename,
'file_handle': tmp_schema_file_handle,
'file_mime_type': 'application/json',
}
return schema_file_to_upload
def _upload_to_gcs(self, file_to_upload):
"""Upload a file (data split or schema .json file) to Google Cloud Storage."""
hook = GCSHook(
gcp_conn_id=self.gcp_conn_id,
delegate_to=self.delegate_to,
impersonation_chain=self.impersonation_chain,
)
hook.upload(
self.bucket,
file_to_upload.get('file_name'),
file_to_upload.get('file_handle').name,
mime_type=file_to_upload.get('file_mime_type'),
gzip=self.gzip if file_to_upload.get('file_name') != self.schema_filename else False,
)