Flask-SQLAlchemy.like () method raises NotImplementedError

I am unable to create a Flask-SQLAlchemy query with a method like()

that is supposed to build a query using an SQL statement LIKE

.

According to SQLAlchemy docs, the method LIKE

can be called on a column like this:

select([sometable]).where(sometable.c.column.like("%foobar%")) 

      

        
        
        
      

    

I have a ModelClass that subclasses the Flask-SQLAlchemy class db.Model

. Defined as follows:

class ModelClass(db.Model):
    # Some other columns ... 
    field1 = db.Column(db.Integer(), db.ForeignKey('my_other_class.id'))
    rel1 = db.relationship("MyOtherClass", foreign_keys=[field1])

      

        
        
        
      

    

Then I have a loop in which I create filters dynamically. Outside of the loop, I use these filters to filter the request. The inside of my loop, slightly modified, looks like this:

search_term = '%{}%'.format(search_string)
my_filter = getattr(ModelClass, field_string).like(search_term)

      

        
        
        
      

    

This throws an error in line with the method LIKE

:

NotImplementedError: <function like_op at 0x101c06668>

      

        
        
        
      

    

It throws this error for any text string. Python docs for NotImplementedError

says:

This exception is derived from RuntimeError. In userbase classes, abstract methods should throw this exception when they require derived classes to override the method.

It is not AttributeError

, so I think the method LIKE

exists, but something else is wrong and I'm not sure what.

Update

Now that I look in more detail at the model definition, I think the problem might be that I am doing this on a relation, not a type Column

.

I saw what type(getattr(ModelClass, field_string))

gives:

<sqlalchemy.orm.attributes.InstrumentedAttribute object at 0x102018090>

      

        
        
        
      

    

Since it is not a type Column

, I looked at the values ​​for field_string

and saw that one of the passed values ​​actually was rel1

.

So, I think that the "answer", but I'm still confused why the call .like()

to rel1

not call AttributeError

.