Why is peewee not nesting this WHERE clause correctly?

Question

I'm creating a query like this in the Python peewee ORM:

myTableModel.records = myTableModel.select(
    myTableModel.table_field_name
    ).where(
    (myTableModel.second_field_name.is_null(True) |
    myTableModel.second_field_name == "")
    )

I can work back to the SQL generated by running print myTableModel.records.sql()

SELECT `t1`.`table_field_name`
FROM `table_name` AS t1
WHERE (((`t1`.`second_field_name` IS NULL) OR `t1`.`second_field_name`) = '');

This is not using the correct nesting. This is the statement I want:

SELECT `t1`.`table_field_name`
FROM `table_name` AS t1
WHERE `t1`.`second_field_name` IS NULL OR `t1`.`second_field_name` = '';

The existing WHERE clause boils down to this ...

WHERE `t1`.`second_field_name` IS NULL = ''

... which produces exactly the opposite of what I want, returning all rows where second_field_name is not NULL.

How do I fix this? Did I nest the Python code incorrectly somehow?

Answer 1

Through trial and error, I've found that adding two more parentheses fixes the query. Parentheses must be added around myTableModel.second_field_name == "" like so:

myTableModel.records = myTableModel.select(
    myTableModel.table_field_name
    ).where(
    (myTableModel.second_field_name.is_null(True) |
    (myTableModel.second_field_name == ""))
    )

I'm not sure exactly why this helps. It seems like Python and peewee ought to be able to use the pipe and outer parentheses as delimiters.