str
An option to control the selection of optimizer version.
This parameter allows individual queries to pick different
query optimizer versions.
Specifying "latest" as a value instructs Cloud Spanner to
use the latest supported query optimizer version. If not
specified, Cloud Spanner uses optimizer version set at the
database level options. Any other positive integer (from the
list of supported optimizer versions) overrides the default
optimizer version for query execution. The list of supported
optimizer versions can be queried from
SPANNER_SYS.SUPPORTED_OPTIMIZER_VERSIONS. Executing a SQL
statement with an invalid optimizer version will fail with a
syntax error (``INVALID_ARGUMENT``) status.
The ``optimizer_version`` statement hint has precedence over
this setting.
