bug: Interval precision is None when ibis handle interval type of BigQuery

[grieve54706]

What happened?

When selecting interval or getting the return type is interval, ibis can't handle the type in the schema to ibis type

ibis.bigquery.connect(...).sql('SELECT INTERVAL '1' DAY AS col')

I found the type that bigquery python client returned is not with precision in the schema.

ibis/ibis/backends/bigquery/__init__.py

Lines 651 to 657 in 11f8921

	def _get_schema_using_query(self, query: str) -> sch.Schema:
	job = self.client.query(
	query,
	job_config=bq.QueryJobConfig(dry_run=True, use_query_cache=False),
	project=self.billing_project,
	)
	return BigQuerySchema.to_ibis(job.schema)

And the _from_sqlglot_INTERVAL of SqlglotType uses a class field default_interval_precision.

ibis/ibis/backends/sql/datatypes.py

Lines 290 to 311 in b16db6a

	def _from_sqlglot_INTERVAL(
	cls,
	precision_or_span: sge.IntervalSpan | None = None,
	nullable: bool | None = None,
	) -> dt.Interval:
	if precision_or_span is None:
	precision_or_span = cls.default_interval_precision
	if isinstance(precision_or_span, str):
	return dt.Interval(precision_or_span, nullable=nullable)
	elif isinstance(precision_or_span, sge.IntervalSpan):
	if (expression := precision_or_span.expression) is not None:
	unit = expression.this
	else:
	unit = precision_or_span.this.this
	return dt.Interval(unit=unit, nullable=nullable)
	elif isinstance(precision_or_span, sge.Var):
	return dt.Interval(unit=precision_or_span.this, nullable=nullable)
	elif precision_or_span is None:
	raise com.IbisTypeError("Interval precision is None")
	else:
	raise com.IbisTypeError(precision_or_span)

The class BigQueryType does not implement it. I am not sure this issue should just make the default_interval_precision with a unit will be okay.

What version of ibis are you using?

9.5.0

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

bigquery

Relevant log output

../app/model/connector.py:45: in query
    return self.connection.sql(sql).limit(limit).to_pandas()
../.venv/lib/python3.11/site-packages/ibis/backends/sql/__init__.py:176: in sql
    schema = self._get_schema_using_query(query)
../.venv/lib/python3.11/site-packages/ibis/backends/bigquery/__init__.py:659: in _get_schema_using_query
    return BigQuerySchema.to_ibis(job.schema)
../.venv/lib/python3.11/site-packages/ibis/backends/bigquery/datatypes.py:67: in to_ibis
    return sch.Schema({f.name: cls._dtype_from_bigquery_field(f) for f in fields})
../.venv/lib/python3.11/site-packages/ibis/backends/bigquery/datatypes.py:67: in <dictcomp>
    return sch.Schema({f.name: cls._dtype_from_bigquery_field(f) for f in fields})
../.venv/lib/python3.11/site-packages/ibis/backends/bigquery/datatypes.py:52: in _dtype_from_bigquery_field
    dtype = BigQueryType.from_string(typ)
../.venv/lib/python3.11/site-packages/ibis/backends/sql/datatypes.py:204: in from_string
    return cls.to_ibis(sgtype, nullable=nullable)
../.venv/lib/python3.11/site-packages/ibis/backends/sql/datatypes.py:173: in to_ibis
    dtype = method(*typ.expressions)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

cls = <class 'app.custom_ibis.backends.sql.datatypes.BigQueryType'>
precision_or_span = None

    @classmethod
    def _from_sqlglot_INTERVAL(
        cls, precision_or_span: sge.IntervalSpan | None = None
    ) -> dt.Interval:
        nullable = cls.default_nullable
        if precision_or_span is None:
            precision_or_span = cls.default_interval_precision
    
        if isinstance(precision_or_span, str):
            return dt.Interval(precision_or_span, nullable=nullable)
        elif isinstance(precision_or_span, sge.IntervalSpan):
            if (expression := precision_or_span.expression) is not None:
                unit = expression.this
            else:
                unit = precision_or_span.this.this
            return dt.Interval(unit=unit, nullable=nullable)
        elif isinstance(precision_or_span, sge.Var):
            return dt.Interval(unit=precision_or_span.this, nullable=nullable)
        elif precision_or_span is None:
>           raise com.IbisTypeError("Interval precision is None")
E           ibis.common.exceptions.IbisTypeError: Interval precision is None

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