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https://issues.apache.org/jira/browse/BEAM-1440?focusedWorklogId=339983&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-339983
]
ASF GitHub Bot logged work on BEAM-1440:
----------------------------------------
Author: ASF GitHub Bot
Created on: 07/Nov/19 15:00
Start Date: 07/Nov/19 15:00
Worklog Time Spent: 10m
Work Description: kamilwu commented on pull request #9772: [BEAM-1440]
Create a BigQuery source that implements iobase.BoundedSource for Python
URL: https://github.com/apache/beam/pull/9772#discussion_r343697148
##########
File path: sdks/python/apache_beam/io/gcp/bigquery.py
##########
@@ -496,6 +506,189 @@ def reader(self, test_bigquery_client=None):
kms_key=self.kms_key)
+FieldSchema = collections.namedtuple('FieldSchema', 'fields mode name type')
+
+
+def _to_bool(value):
+ return value == 'true'
+
+
+def _to_decimal(value):
+ return decimal.Decimal(value)
+
+
+def _to_bytes(value):
+ """Converts value from str to bytes on Python 3.x. Does nothing on
+ Python 2.7."""
+ return value.encode('utf-8')
+
+
+class _JsonToDictCoder(coders.Coder):
+ """A coder for a JSON string to a Python dict."""
+
+ def __init__(self, table_schema):
+ self.fields = self._convert_to_tuple(table_schema.fields)
+ self._converters = {
+ 'INTEGER': int,
+ 'INT64': int,
+ 'FLOAT': float,
+ 'BOOLEAN': _to_bool,
+ 'NUMERIC': _to_decimal,
+ 'BYTES': _to_bytes,
+ }
+
+ @classmethod
+ def _convert_to_tuple(cls, table_field_schemas):
+ """Recursively converts the list of TableFieldSchema instances to the
+ list of tuples to prevent errors when pickling and unpickling
Review comment:
This error was quite interesting. It seems that it's impossible to serialize
and deserialize nested `bigquery.TableFieldSchema` instances:
```
from apache_beam.internal import pickler
from apache_beam.io.gcp.internal.clients import bigquery
obj = bigquery.TableFieldSchema(fields=[bigquery.TableFieldSchema()])
pickler.loads(pickler.dumps(obj))
```
This snippet triggers the following exception:
`AttributeError: 'FieldList' object has no attribute '_FieldList__field'`.
My workaround was to rewrite all TableFieldSchema instances to an equivalent
tuple, which can be serialized and deserialized without problems.
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Issue Time Tracking
-------------------
Worklog Id: (was: 339983)
Time Spent: 9.5h (was: 9h 20m)
> Create a BigQuery source (that implements iobase.BoundedSource) for Python SDK
> ------------------------------------------------------------------------------
>
> Key: BEAM-1440
> URL: https://issues.apache.org/jira/browse/BEAM-1440
> Project: Beam
> Issue Type: New Feature
> Components: sdk-py-core
> Reporter: Chamikara Madhusanka Jayalath
> Assignee: Kamil Wasilewski
> Priority: Major
> Time Spent: 9.5h
> Remaining Estimate: 0h
>
> Currently we have a BigQuery native source for Python SDK [1].
> This can only be used by Dataflow runner.
> We should implement a Beam BigQuery source that implements
> iobase.BoundedSource [2] interface so that other runners that try to use
> Python SDK can read from BigQuery as well. Java SDK already has a Beam
> BigQuery source [3].
> [1]
> https://github.com/apache/beam/blob/master/sdks/python/apache_beam/io/gcp/bigquery.py
> [2]
> https://github.com/apache/beam/blob/master/sdks/python/apache_beam/io/iobase.py#L70
> [3]
> https://github.com/apache/beam/blob/master/sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigquery/BigQueryIO.java#L1189
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