Why the pymysql cursor increase the memory?

Question

When I use python 3.9 and pymysql 1.1.0, I find the memory will increase after I get data from cursor. I need run a model in cycle way. The input datas need download from mysql database.I use dbutils to manager my pymysql connection. Then I use memory_profiler to check the code that I find the memory increase when I use "for row in cursor:". What should I do to fix the problem? Thank you!

    def databaseSelect(dataConnect,unit, kkspoint, kksname, starttime, endtimePlus):
        conn = dataConnect.connection()
        cursor = conn.cursor()  
        backdict = {}
        data1 = {}
        tables = []
        data = []
        unit = str(unit)
        kkspoint = str(kkspoint)
        kksname = str(kksname)
        starttime = str(starttime)
        endtimePlus = int(endtimePlus)
        starttime = datetime.datetime.strptime(starttime, "%Y-%m-%d %H:%M:%S")
        endtime = (starttime + datetime.timedelta(minutes=endtimePlus)).strftime('%Y-%m-%d %H:%M:%S')
        sql = 'show tables;'
        cursor.execute(sql)

        for row in cursor:
            # print('#' * 50 + "checkpoint5" + '#' * 50)
            # print(row)
            tables.append(str(row[0].decode('utf-8')))
            del row
        cursor = conn.close()
        conn.close()
        del (cursor,conn)
        findState = False
        for table in tables:
            a = table.split('y')[0].split('a')[2]
            if a == kkspoint:
                b = table.split('y')[1].split('m')[0]
                c = table.split('y')[1].split('m')[1].split('d')
                times = b + '-' + c[0] + '-' + c[1] + ' 00:00:00'
                originTime = datetime.datetime.strptime(times, '%Y-%m-%d %H:%M:%S')
                backdict.setdefault(a, []).append(originTime)
                del (a,b,c,times,originTime)
            del table
        for key in backdict.keys():
            backdict[key].sort()
            data1[key] = backdict[key]
            for i, timefind in enumerate(data1[key]):
                if starttime >= timefind and starttime < backdict[key][i + 1]:
                    checkTimeFind = timefind
                    findState = True
                    break
            if findState:
                break
            del key

        if unit == 'zj':
            kkspoint = 'Data' + kkspoint + 'y' + str(checkTimeFind.year) + 'm' + str(
                checkTimeFind.month) + 'd' + str(
                checkTimeFind.day)
        elif unit == 'fw':
            kkspoint = 'fwData' + kkspoint + 'y' + str(checkTimeFind.year) + 'm' + str(
                checkTimeFind.month) + 'd' + str(
                checkTimeFind.day)
        else:
            print('#' * 100 + '\nIPdownloader.databaseSelect\nwrong unit')
            raise IndexError

        sql = "select {} from {} where time between '{}' and '{}';".format(kksname, kkspoint, starttime, endtime)
        conn = dataConnect.connection()
        cursor = conn.cursor()  
        cursor.execute(sql)
        for row in cursor:
            data.append(row)
            del row
        cursor.close()
        conn.close()
        del (backdict, data1, sql, tables, cursor, conn, unit, kkspoint, kksname, starttime, endtime, findState)
        return data

Answer 1

I find the problem is the pandas bring after the pymysql back the data. In my code I use pandas version is 2.1.0. It will leave a weakref during the code running one time. So that the memory will increase. The problem fixed after I change the pandas version to 1.5.3. Now It is seem good.