Class BatchSnapshot (3.66.0)

BatchSnapshot(
    database,
    read_timestamp=None,
    exact_staleness=None,
    session_id=None,
    transaction_id=None,
    client_context=None,
)

Wrapper for generating and processing read / query batches.

Parameters
Name	Description
`database`	`Database` database to use
`read_timestamp`	`datetime.datetime` Execute all reads at the given timestamp.
`exact_staleness`	`datetime.timedelta` Execute all reads at a timestamp that is `exact_staleness` old.

Methods

enter

__enter__()

Begin with block.

exit

__exit__(exc_type, exc_val, exc_tb)

End with block.

close

close()

Clean up underlying session.

execute_sql

execute_sql(*args, **kw)

Convenience method: perform query operation via snapshot.

See execute_sql.

from_dict

from_dict(database, mapping)

Reconstruct an instance from a mapping.

Parameters
Name	Description
`database`	`Database` database to use
`mapping`	`mapping` serialized state of the instance

generate_query_batches

generate_query_batches(
    sql,
    params=None,
    param_types=None,
    partition_size_bytes=None,
    max_partitions=None,
    query_options=None,
    data_boost_enabled=False,
    directed_read_options=None,
    *,
    retry=_MethodDefault._DEFAULT_VALUE,
    timeout=_MethodDefault._DEFAULT_VALUE
)

Start a partitioned query operation.

generate_read_batches

generate_read_batches(
    table,
    columns,
    keyset,
    index="",
    partition_size_bytes=None,
    max_partitions=None,
    data_boost_enabled=False,
    directed_read_options=None,
    *,
    retry=_MethodDefault._DEFAULT_VALUE,
    timeout=_MethodDefault._DEFAULT_VALUE
)

Start a partitioned batch read operation.

process

process(batch)

Process a single, partitioned query or read.

process_query_batch

process_query_batch(
    batch,
    *,
    lazy_decode: bool = False,
    retry=_MethodDefault._DEFAULT_VALUE,
    timeout=_MethodDefault._DEFAULT_VALUE
)

Process a single, partitioned query.

process_read_batch

process_read_batch(
    batch,
    *,
    retry=_MethodDefault._DEFAULT_VALUE,
    timeout=_MethodDefault._DEFAULT_VALUE,
    lazy_decode=False
)

Process a single, partitioned read.

read

read(*args, **kw)

Convenience method: perform read operation via snapshot.

See read.

run_partitioned_query

run_partitioned_query(
    sql,
    params=None,
    param_types=None,
    partition_size_bytes=None,
    max_partitions=None,
    query_options=None,
    data_boost_enabled=False,
    lazy_decode=False,
)

Start a partitioned query operation to get list of partitions and then executes each partition on a separate thread

to_dict

to_dict()

Return state as a dictionary.

Result can be used to serialize the instance and reconstitute it later using from_dict.