Why does the Table metadata show zero rows when querying the table returns rows?

Question

I have inserted data into a Table in Cloud Datalab. When I look at the table metadata it says the table has size 0, but if I query or sample the table I can see data. What gives?

Answer 1

When inserting data into a BigQuery table, it passes through a 'streaming buffer'. The BigQuery APIs return the following when metadata is queried:

• numBytes - The size of this table in bytes, excluding any data in the streaming buffer.
• numRows - The number of rows of data in this table, excluding any data in the streaming buffer.

The metadata will eventually show the correct values but it can take some time.

(Note: this is an issue with the BigQuery API, not a Datalab issue per-se).