How do I check if an insert was successful with MySQLdb in Python?

Question

I have this code:

cursor = conn.cursor()
cursor.execute(("insert into new_files (videos_id, filename, "
                "is_processing) values (%s,%s,1)"), (id, filename))
logging.warn("%d", cursor.rowcount)
if (cursor.rowcount == 1):
    logging.info("inserted values %d, %s", id, filename)
else:
    logging.warn("failed to insert values %d, %s", id, filename)
cursor.close()

Fun as it is, cursor.rowcount is always one, even though i updated my database to make the videos_id a unique key. That is, the insert fails because in my tests the same videos_id is going to appear (and when I check the database, nothing was inserted). But for whatever reason, the rowcount is always 1 - even the logging.warn I have spits out a rowcount of 1.

So, the question:
Can I use rowcount to work out if an insert went fine? If so, what am I (presumably) doing wrong? otherwise, how do i check if an insert went fine?

Answer 1

Your code does not commit after the modifications (your modifications are rolled back). That is you should add the following line after cursor.execute:

conn.commit()

Failed insert will throw MySQLdb.IntegrityError, so you should be ready to catch it.

Thus, your code should look something like:

sql_insert = """insert into new_files (videos_id, filename, is_processing)
values (%s,%s,1)"""

cursor = conn.cursor()
try:
    affected_count = cursor.execute(sql_insert, (id, filename))
    conn.commit()
    logging.warn("%d", affected_count)
    logging.info("inserted values %d, %s", id, filename)
except MySQLdb.IntegrityError:
    logging.warn("failed to insert values %d, %s", id, filename)
finally:
   cursor.close()

Answer 2

I don't have enough reputation to make a comment, but here's an important note:

It is also possible for execute() to fail silently if you don't commit after the call. Namely, MyISAM tables don't require the commit, but InnoDB ones do.

Answer 3

If the insert fails you'll get a raised exception or someone will yell or you'll fall off your chair.

Answer 4

How about using a try/catch block instead of looking at rowcount. If it catches an exception then there is a problem; otherwise, no problem.

Answer 5

Store the insert statement in the string and print it after. If an exception occurs the statement won't print.

sql_insert = """insert into new_files (videos_id, filename, is_processing)
values (%s,%s,1)"""
cur.execute(sql_insert)
print('Executed:', sql_insert)