duckdb with thread

example_thread.py

from multiprocessing import connection
from time import sleep, perf_counter
from threading import Thread
import duckdb

con = duckdb.connect(database=':memory:')
con.execute("CREATE TABLE items(item VARCHAR, value DECIMAL(10,2), count INTEGER)")
con.execute("INSERT INTO items VALUES ('jeans', 20.0, 42), ('hammer', 42.2, 4242)")


def task(a):
    print(a)
    cursor = con.cursor()
    cursor.execute("SELECT * FROM items WHERE count=?", [a])
    print(cursor.fetchall())
    sleep(1)
    print('done')


start_time = perf_counter()

# create two new threads
t1 = Thread(target=task, args=[42])
t2 = Thread(target=task, args=[4242])

# start the threads
t1.start()
t2.start()

# wait for the threads to complete
t1.join()
t2.join()

end_time = perf_counter()

print(f'It took {end_time- start_time: 0.2f} second(s) to complete.')

Did something changed in the duckdb API?

I am getting the error with the exact same code

 DuckDB objects created in a thread can only be used in that same thread. The object was created in thread id 4236038043693429136 and this is thread id 18260946403773551314

I am using

• duckdb: 0.3.4-dev72
• OS: MacOS 12.1 (M1 MAX)

@Raidus, I don't know what changed exactly but I confirm there was some changes between 0.3.4 and 0.4.0 in thread API. I tested on MacOS (M1) and it works.