Class Snapshot (3.3.0)

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Snapshot(
    session,
    read_timestamp=None,
    min_read_timestamp=None,
    max_staleness=None,
    exact_staleness=None,
    multi_use=False,
)

Allow a set of reads / SQL statements with shared staleness.

See https://cloud.google.com/spanner/reference/rpc/google.spanner.v1#google.spanner.v1.TransactionOptions.ReadOnly

If no options are passed, reads will use the strong model, reading at a timestamp where all previously committed transactions are visible.

Parameters

NameDescription
session Session

The session used to perform the commit.

read_timestamp `datetime.datetime`

Execute all reads at the given timestamp.

min_read_timestamp `datetime.datetime`

Execute all reads at a timestamp >= min_read_timestamp.

max_staleness `datetime.timedelta`

Read data at a timestamp >= NOW - max_staleness seconds.

exact_staleness `datetime.timedelta`

Execute all reads at a timestamp that is exact_staleness old.

multi_use `bool`

If true, multiple read / execute_sql calls can be performed with the snapshot in the context of a read-only transaction, used to ensure isolation / consistency. Incompatible with max_staleness and min_read_timestamp.

Inheritance

builtins.object > google.cloud.spanner_v1._helpers._SessionWrapper > google.cloud.spanner_v1.snapshot._SnapshotBase > Snapshot

Methods

begin

begin()

Begin a read-only transaction on the database.

Exceptions
TypeDescription
ValueErrorif the transaction is already begun, committed, or rolled back.
Returns
TypeDescription
bytesthe ID for the newly-begun transaction.

execute_sql

execute_sql(sql, params=None, param_types=None, query_mode=None, query_options=None, partition=None, retry=<object object>, timeout=<object object>)

Perform an ExecuteStreamingSql API request.

Parameters
NameDescription
sql str

SQL query statement

params dict, {str -> column value}

values for parameter replacement. Keys must match the names used in sql.

param_types dict[str -> Union[dict, .types.Type]]

(Optional) maps explicit types for one or more param values; required if parameters are passed.

query_mode QueryMode

Mode governing return of results / query plan. See: QueryMode <https://cloud.google.com/spanner/reference/rpc/google.spanner.v1#google.spanner.v1.ExecuteSqlRequest.QueryMode>_.

query_options QueryOptions or `dict`

(Optional) Query optimizer configuration to use for the given query. If a dict is provided, it must be of the same form as the protobuf message QueryOptions

partition bytes

(Optional) one of the partition tokens returned from partition_query.

retry `google.api_core.retry.Retry`

(Optional) The retry settings for this request.

timeout float

(Optional) The timeout for this request.

Exceptions
TypeDescription
ValueErrorfor reuse of single-use snapshots, or if a transaction ID is already pending for multiple-use snapshots.
Returns
TypeDescription
StreamedResultSeta result set instance which can be used to consume rows.

partition_query

partition_query(sql, params=None, param_types=None, partition_size_bytes=None, max_partitions=None, *, retry=<object object>, timeout=<object object>)

Perform a PartitionQuery API request.

Parameters
NameDescription
sql str

SQL query statement

params dict, {str -> column value}

values for parameter replacement. Keys must match the names used in sql.

param_types dict[str -> Union[dict, .types.Type]]

(Optional) maps explicit types for one or more param values; required if parameters are passed.

partition_size_bytes int

(Optional) desired size for each partition generated. The service uses this as a hint, the actual partition size may differ.

max_partitions int

(Optional) desired maximum number of partitions generated. The service uses this as a hint, the actual number of partitions may differ.

retry `google.api_core.retry.Retry`

(Optional) The retry settings for this request.

timeout float

(Optional) The timeout for this request.

Exceptions
TypeDescription
ValueErrorfor single-use snapshots, or if a transaction ID is already associated with the snapshot.
Returns
TypeDescription
iterable of bytesa sequence of partition tokens

partition_read

partition_read(table, columns, keyset, index='', partition_size_bytes=None, max_partitions=None, *, retry=<object object>, timeout=<object object>)

Perform a PartitionRead API request for rows in a table.

Parameters
NameDescription
table str

name of the table from which to fetch data

columns list of str

names of columns to be retrieved

keyset KeySet

keys / ranges identifying rows to be retrieved

index str

(Optional) name of index to use, rather than the table's primary key

partition_size_bytes int

(Optional) desired size for each partition generated. The service uses this as a hint, the actual partition size may differ.

max_partitions int

(Optional) desired maximum number of partitions generated. The service uses this as a hint, the actual number of partitions may differ.

retry `google.api_core.retry.Retry`

(Optional) The retry settings for this request.

timeout float

(Optional) The timeout for this request.

Exceptions
TypeDescription
ValueErrorfor single-use snapshots, or if a transaction ID is already associated with the snapshot.
Returns
TypeDescription
iterable of bytesa sequence of partition tokens

read

read(table, columns, keyset, index='', limit=0, partition=None, *, retry=<object object>, timeout=<object object>)

Perform a StreamingRead API request for rows in a table.

Parameters
NameDescription
table str

name of the table from which to fetch data

columns list of str

names of columns to be retrieved

keyset KeySet

keys / ranges identifying rows to be retrieved

index str

(Optional) name of index to use, rather than the table's primary key

limit int

(Optional) maximum number of rows to return. Incompatible with partition.

partition bytes

(Optional) one of the partition tokens returned from partition_read. Incompatible with limit.

retry `google.api_core.retry.Retry`

(Optional) The retry settings for this request.

timeout float

(Optional) The timeout for this request.

Exceptions
TypeDescription
ValueErrorfor reuse of single-use snapshots, or if a transaction ID is already pending for multiple-use snapshots.
Returns
TypeDescription
StreamedResultSeta result set instance which can be used to consume rows.