Python code to cancel a running Oracle SQL Query

问题

I have the following python code which runs multiple SQL Queries in Oracle database and combines them into one dataframe.

The queries exist in a txt file and every row is a separate SQL query. The loop runs sequentially the queries. I want to cancel any SQL queries that run for more than 10 secs so as not to create an overhead in the database. The following code doesnt actually me give the results that i want. More specifically this bit of the code really help me on my issue:

        if (time.time() - start) > 10: 
        connection.cancel()

Full python code is the following. Probably it is an oracle function that can be called so as to cancel the query.

import pandas as pd
import cx_Oracle
import time

ip = 'XX.XX.XX.XX'
port = XXXX
svc  = 'XXXXXX'
dsn_tns = cx_Oracle.makedsn(ip, port, service_name = svc)

connection = cx_Oracle.connect(user='XXXXXX'
                           , password='XXXXXX'
                           , dsn=dsn_tns
                           , encoding = "UTF-8"   
                           , nencoding = "UTF-8"  
                           )

filepath = 'C:/XXXXX'

appended_data = []

with open(filepath + 'sql_queries.txt') as fp:  
    line = fp.readline()
    while line:
        start = time.time()
        df = pd.read_sql(line, con=connection)
        if (time.time() - start) > 10: 
            connection.cancel()
            print("Cancel")         
        appended_data.append(df)
        df_combined = pd.concat(appended_data, axis=0)
        line = fp.readline()
        print(time.time() - start)
    fp.close()

回答1:

A better approach would be to spend some time tuning the queries to make them as efficient as necessary. As @Andrew points out we can't easily kill a database query from outside the database - or even from another session inside the database (it requires DBA level privileges).

Indeed, most DBAs would rather you ran a query for 20 seconds rather than attempt to kill every query which runs more than 10. Apart from anything else, having a process which polls you query to see how long it's been running for is itself a waste of database resources.

I suggest you discuss this with your DBA. You may find you're worrying about nothing.

回答2:

Look at cx_Oracle 7's Connection.callTimeout setting. You'll need to be using Oracle client libraries 18+. (These will connect to Oracle DB 11.2+). The doc for the equivalent node-oracledb parameter explains the fine print behind the Oracle behavior and round trips.

来源：https://stackoverflow.com/questions/53296152/python-code-to-cancel-a-running-oracle-sql-query