I have a large table with millions of records in MySQL incident_archive and I want to sort the rows by the created column and keep the first X rows and delete the rest OK, what's the most efficient way.
So far I've come up with this solution in Python:
def do_delete_archive(rowsToKeep):
if rowsToKeep > 0:
db_name = find_environment_value('DB_NAME', False, "dbname")
db_host = find_environment_value('DB_HOST', False, "host")
db_user = find_environment_value('DB_USER', False, "username")
db_pass = find_environment_value('DB_PASS', False, "password")
db = MySQLdb.connect(host=db_host,user=db_user,passwd=db_pass,db=db_name)
cursor = db.cursor()
sql = f"""DELETE FROM `incident_archive`
WHERE incident_id NOT IN
( SELECT incident_id FROM
( SELECT incident_id FROM `incident_archive` ORDER BY created DESC LIMIT {rowsToKeep}) foo) LIMIT 10000;"""
try:
rowcount = rowsToKeep+ 1
while rowcount > rowsToKeep:
cursor.execute(sql)
db.commit()
rowcount = cursor.rowcount
print(f"--- Affected Rows: {rowcount} ---")
except:
db.rollback()
The problem I have here is that this method will not work if the value of rowsToKeep is greater than or equal to 10000, what is a better way of doing this process?
**Note: The rowsToKeep value is dynamic, which means it can change.
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I came up with the following solution:
Note: Threshold is the variable containing the maximum number of records we wish to keep at 1000 in our example
sqlCreate = f"""CREATE TABLE new_incident_archive LIKE incident_archive;""" print(f"Running query is: {sqlCreate}") cursor.execute(sqlCreate) print(f"Done with: {sqlCreate}") sqlInsert = f"""INSERT INTO new_incident_archive SELECT * FROM `incident_archive` ORDER BY created DESC LIMIT {threshold}""" print(f"Running query is: {sqlInsert}") cursor.execute(sqlInsert) db.commit() print(f"Done with: {sqlInsert}") sqlDrop = f"""DROP TABLE incident_archive""" print(f"Running query is: {sqlDrop}") cursor.execute(sqlDrop) print(f"Done with: {sqlDrop}") sqlRename = f"""RENAME TABLE `new_incident_archive` TO `incident_archive`;""" print(f"Running query is: {sqlRename}") cursor.execute(sqlRename) print(f"Done with: {sqlRename}")