Module snapshot (1.19.2)

Model a set of read-only queries to a database as a snapshot.

Classes

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.

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

Parameters

Name	Description
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`.