Is your feature request related to a problem? Please describe.
I could not find a way to use SAFE_CAST which returns NULL if the cast fails rather than failing the query.
Describe the solution you'd like
A custom safe_cast function provided by the library that compiles to SAFE_CAST.
Describe alternatives you've considered
I can implement a custom safe_cast function within my codebase. But, I would have to subclass sqlalchemy.sql.Cast (say SafeCast) and override the visit_cast function in the bigquery dialect to compile SafeCast into SAFE_CAST(...) instead of `CAST(...).
class SafeCast(Cast):
pass
def safe_cast(col: ColumnElement, type_: TypeEngine)) -> SafeCast:
return SafeCast(col, type_)
# Define custom Bigquery dialect and compiler with
def visit_cast(self, cast, **kwargs):
if isinstance(cast, SafeCast):
return "SAFE_CAST(%s AS %s)" % (
cast.clause._compiler_dispatch(self, **kwargs),
cast.typeclause._compiler_dispatch(self, **kwargs),
)
else:
return super().visit_cast(cast, **kwargs)
Additional context
Add any other context or screenshots about the feature request here.
Is your feature request related to a problem? Please describe. I could not find a way to use SAFE_CAST which returns NULL if the cast fails rather than failing the query.
Describe the solution you'd like A custom
safe_castfunction provided by the library that compiles toSAFE_CAST.Describe alternatives you've considered I can implement a custom
safe_castfunction within my codebase. But, I would have to subclasssqlalchemy.sql.Cast(saySafeCast) and override thevisit_castfunction in the bigquery dialect to compileSafeCastintoSAFE_CAST(...)instead of `CAST(...).Additional context Add any other context or screenshots about the feature request here.