How to fix error when using OR and custom function?

Question

Python

Function

def lower_string(_str):
    return _str.lower()

I add to the database and execute the request
con.create_function("LOWER", 1, lower_string)

SELECT * FROM incoming WHERE lower("index") LIKE lower("%иванов%")

The function works fine, but as soon as I add OR

SELECT * FROM incoming WHERE lower("index") LIKE lower("%иванов%") OR
lower("num_incoming") LIKE lower("%иванов%")

then an error occurs immediately.

sqlite3.OperationalError: user-defined function raised exception

Why does the error occur only if there is an OR, and how can it be fixed?

Answer 1

Everything turned out to be quite obvious: Since not all fields in the table were of string type, the lower() function could not process them. To fix the error, I simply added a conversion to the string:

def lower_string(_str):
    return str(_str).lower()

Answer 2

Why write your own function when there is a built-in one?
https://www.w3resource.com/sqlite/core-functions-l...