Class ReadRowsStream (2.27.0)

ReadRowsStream(client, name, offset, read_rows_kwargs, retry_delay_callback=None)

A stream of results from a read rows request.

This stream is an iterable of ReadRowsResponse. Iterate over it to fetch all row messages.

If the fastavro library is installed, use the rows() method to parse all messages into a stream of row dictionaries.

If the pandas and fastavro libraries are installed, use the to_dataframe() method to parse all messages into a pandas.DataFrame.

This object should not be created directly, but is returned by other methods in this library.

Methods

ReadRowsStream(client, name, offset, read_rows_kwargs, retry_delay_callback=None)

Construct a ReadRowsStream.

Parameters
Name	Description
`client`	`google.cloud.bigquery_storage_v1.services big_query_read.BigQueryReadClient` A GAPIC client used to reconnect to a ReadRows stream. This must be the GAPIC client to avoid a circular dependency on this class.
`name`	`str` Required. Stream ID from which rows are being read.
`offset`	`int` Required. Position in the stream to start reading from. The offset requested must be less than the last row read from ReadRows. Requesting a larger offset is undefined.
`read_rows_kwargs`	`dict` Keyword arguments to use when reconnecting to a ReadRows stream.
`retry_delay_callback`	`Optional[Callable[[float], None]]` If the client receives a retryable error that asks the client to delay its next attempt and retry_delay_callback is not None, ReadRowsStream will call retry_delay_callback with the delay duration (in seconds) before it starts sleeping until the next attempt.

Returns
Type	Description
`Iterable[ google.cloud.bigquery_storage_v1.servicesReadRowsResponse ]`	A sequence of row messages.

__iter__()

An iterable of messages.

Returns
Type	Description
`Iterable[ ReadRowsResponse ]`	A sequence of row messages.

rows(read_session=None)

Iterate over all rows in the stream.

This method requires the fastavro library in order to parse row messages in avro format. For arrow format messages, the pyarrow library is required.

Parameter
Name	Description
`read_session`	`Optional[ReadSession]` This argument was used to specify the schema of the rows in the stream, but now the first message in a read stream contains this information. When row_restriction is applied, some streams may be empty without read_session info. Provide this argument to avoid an error. For more information, see https://github.com/googleapis/python-bigquery-storage/issues/733

Returns
Type	Description
`Iterable[Mapping]`	A sequence of rows, represented as dictionaries.

to_arrow(read_session=None)

Create a pyarrow.Table of all rows in the stream.

This method requires the pyarrow library and a stream using the Arrow format.

Parameter
Name	Description
`read_session`	`ReadSession` This argument was used to specify the schema of the rows in the stream, but now the first message in a read stream contains this information. When row_restriction is applied, some streams may be empty without read_session info. Provide this argument to avoid an error. For more information, see https://github.com/googleapis/python-bigquery-storage/issues/733

Returns
Type	Description
`pyarrow.Table`	A table of all rows in the stream.

to_dataframe(read_session=None, dtypes=None)

Create a pandas.DataFrame of all rows in the stream.

This method requires the pandas libary to create a data frame and the fastavro library to parse row messages.

Parameters
Name	Description
`read_session`	`ReadSession` This argument was used to specify the schema of the rows in the stream, but now the first message in a read stream contains this information. When row_restriction is applied, some streams may be empty without read_session info. Provide this argument to avoid an error. For more information, see https://github.com/googleapis/python-bigquery-storage/issues/733
`dtypes`	`Map[str, Union[str, pandas.Series.dtype]]` Optional. A dictionary of column names pandas `dtype`s. The provided `dtype` is used when constructing the series for the column specified. Otherwise, the default pandas behavior is used.

Returns
Type	Description
`pandas.DataFrame`	A data frame of all rows in the stream.