Memory leak while continuously inserting/updating data

I'm running the connector to feed IOT data from a broker into MariaDB tables. It opens a single connection and uses a single cursor. The values for "pyformat" style are specified as a dict.

While running the script I can watch the script continuously growing up to several GB during a few hours.

I already checked that it is related to the MariaDB actions by commenting out the three execute() calls, what is completely stopping memory growth.

I also checked what would happen if I do a cyclic cursor.close() and connection.close(), but no change, memory is not getting released.

If any additional information is required please let me know.

Update 2020-08-22:
In order to help to track this down I just changed the whole insertion process to just one line which calls a stored procedure with 4 parameters (varchar(15), datetime, char(1), varchar(512)). The memory leak is still clearly visible, memory usage is continuously increasing.

CREATE TABLE `leak` (

  `a` varchar(15) COLLATE utf8_bin NOT NULL,

  `b` datetime NOT NULL,

  `c` char(1) COLLATE utf8_bin NOT NULL,

  `d` varchar(512) COLLATE utf8_bin NOT NULL,

  KEY `a` (`a`,`b`)

) ENGINE=ROCKSDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin

Memory size during script run:

Just started:

F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD

0 S  1000 19814 26276 14  80   0 -  7667 poll_s pts/0    00:00:00 demo.py

2:30 runtime:

F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD

0 S  1000 19814 26276  3  80   0 -  9185 poll_s pts/0    00:00:05 demo.py

5:10 runtime:

F S   UID   PID  PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD

0 S  1000 19814 26276  3  80   0 - 10835 poll_s pts/0    00:00:09 demo.py