Values:
OPERATOR_UNSPECIFIED (0):
Unspecified. This value must not be used.
IS_NAN (2):
The given field is equal to NaN.
IS_NULL (3):
The given field is equal to NULL.
IS_NOT_NAN (4):
The given field is not equal to NaN.
Requires:
- No other `NOT_EQUAL`, `NOT_IN`, `IS_NOT_NULL`, or
`IS_NOT_NAN`.
- That `field` comes first in the `order_by`.
IS_NOT_NULL (5):
The given `field` is not equal to `NULL`.
Requires:
- A single `NOT_EQUAL`, `NOT_IN`, `IS_NOT_NULL`, or
`IS_NOT_NAN`.
- That `field` comes first in the `order_by`.