I want to insert given values from my docker app-service to the MariaDB-service.
The connection has been established because I can execute SELECT * FROM
via the MariaDB.connection.cursor
.
First of all I create the connection:
def get_conn() -> mariadb.connection:
try:
conn = mariadb.connect(
user="XXX",
database="XXX",
password="XXX",
host="db",
port=33030,
)
except mariadb.Error as e:
print(f'Error connecting to MariaDB Platform: {e}')
sys.exit(1)
return conn
Then I create a mariadb.connection.cursor
-Object:
def get_cur() -> mariadb.connection.cursor:
conn = get_conn()
cur = conn.cursor()
return cur
Finally I want to insert new values in the table testing
:
def write_data():
cursor = get_cur()
conn = get_conn()
cursor.execute('INSERT INTO testing (title) VALUE ("2nd automatic entry");')
print("Executed Query")
conn.commit()
cursor.close()
conn.close()
print("Closed Connection")
return True
To test, if the entries are inserted, I started with 1 manual entry, then executed the write_data()
-function and to finish of I inserted a 2nd manual entry via the console.
After the procedure the table looks like:
Note that the ÃŽd
is on AUTO_INCREMENT. So the function write_data()
was not skipped entirely, because the 2nd manual entry got the id 3 and not 2.
2
Answers
It’s really easy, in a new table with new code, to unintentionally do an INSERT without a COMMIT. That is especially true using the Python connector, which doesn’t use autocommit. A dropped connection with an open transaction rolls back the transaction. And, a rolled-back INSERT does not release the autoincremented ID value for reuse.
This kind of thing happens, and it’s no cause for alarm.
A wise database programmer won’t rely on a set of autoincrementing IDs with no gaps in it.
You’re committing a transaction in a different connection than the one your cursor belongs to.
get_conn()
creates a new database connection and returns it.get_cur()
callsget_conn
, that gets it a new connection, retrieves a cursor object that belongs to it, and returns it.In your main code, you call
get_conn
– that gives you connection A.Then you obtain a cursor by calling
get_cur
– that creates a connection B and returns a cursor belonging to it.You run
execute
on the cursor object (Connection B) but commit the connection you got in the first call (Connection A).PS: This was a really fun problem to debug, thanks ð