[GitHub] [beam] chunyang commented on a change in pull request #17153: [BEAM-14112] Avoid storing a generator in _CustomBigQuerySource

[GitBox <gi...@apache.org>]

chunyang commented on a change in pull request #17153:
URL: https://github.com/apache/beam/pull/17153#discussion_r832546377



##########
File path: sdks/python/apache_beam/io/gcp/bigquery.py
##########
@@ -657,6 +658,22 @@ def reader(self, test_bigquery_client=None):
         kms_key=self.kms_key)
 
 
+class _BigQueryExportResult:
+  def __init__(self, schema, metadata_list):
+    self.schema = schema
+    self.metadata_list = metadata_list
+
+  # Store schema as JSON string since TableSchema objects cannot be pickled.
+  @property
+  @functools.lru_cache()
+  def schema(self):
+    return bigquery_tools.parse_table_schema_from_json(self._schema)
+
+  @schema.setter
+  def schema(self, value):
+    self._schema = json.dumps(bigquery_tools.table_schema_to_dict(value))

Review comment:
       Are there any guarantees that `json.dumps(bigquery_tools.table_schema_to_dict(x))` and `bigquery_tools.parse_table_schema_from_json(x)` are reciprocal functions?




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