bug: add_operation attempts to call into removed translator_class

[DavidSlayback]

What happened?

Previously (under Ibis 7.2.0), we had defined a SAFE_CAST operation for our usage of Ibis with bigquery with the following:

import ibis
import ibis.expr.datatypes as dt
import ibis.expr.rules as rlz
from ibis.backends.bigquery.datatypes import BigQueryType
from ibis.expr.operations.core import Value as ValueOp
from ibis.expr.types import Value as ValueType


class SafeCast(ValueOp):
    """Safe cast value or column to a specific data type."""

    arg: ValueOp
    to: dt.DataType

    shape = rlz.shape_like("arg")

    @property
    def name(self):  # noqa
        return f"SAFE_CAST({self.arg.name} as {self.to})"

    @property
    def dtype(self):  # noqa
        return self.to


def safe_cast(col, dtype):
    """Safely cast a column to a specific data type."""
    return SafeCast(col, dtype).to_expr()


@ibis.bigquery.add_operation(SafeCast)
def _safe_cast_gbq(translator, expr):
    arg, target_dtype = expr.args
    compiled_arg = translator.translate(arg)
    sql_type = BigQueryType.from_ibis(target_dtype)
    return f"SAFE_CAST({compiled_arg} as {sql_type})"


ValueType.safe_cast = safe_cast

When attempting to update to Ibis 9.0.0, this broke with the error:
AttributeError: 'BigQueryCompiler' object has no attribute 'translator_class'

Not sure if this is a bug or an intended change in the way a user can add an operation to Ibis

What version of ibis are you using?

7.2.0 originally, 9.0.0 for the error

What backend(s) are you using, if any?

BigQuery

Relevant log output

No response

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[gforsyth]

Hey @DavidSlayback -- looks like we forgot to update how add_operation works with the new sqlglot backends. We'll get that fixed up for 9.1, and I'll see if I can get you a workaround in the meantime

[gforsyth]

Hey @DavidSlayback -- I forgot, we added built-in support for try_cast (or SAFE_CAST). That doesn't answer the larger issue about adding custom ops, but for your particular use-case, you can do

some_table.my_int_col.try_cast("float64")

e.g.

[ins] In [1]: import ibis

[ins] In [2]: t = ibis.memtable({"b": [1, 2]})

[ins] In [3]: ibis.to_sql(t.b.try_cast("float64"), dialect="bigquery")
Out[3]: 
SELECT
  SAFE_CAST(`t0`.`b` AS FLOAT64) AS `TryCast_b_ Float64`
FROM `ibis_pandas_memtable_cywg4g55dbgethukk5btbdeyve` AS `t0`

[DavidSlayback]

Thank you! Both for pointing to existing functionality and for considering a fix next release. Overall we get a ton of use out of this project, thanks for building it 😀