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POTwisted - Using a Deferred for another sql query
 

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  1. POTwisted - Using a Deferred for another sql query
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    <p>I've got a twisted based network application. Now I would like to implement a new database design but I''m getting stuck with the Deferred object.</p> <p>I write sessions into my database by using this two functions:</p> <pre><code>def createSession(self, peerIP, peerPort, hostIP, hostPort): SessionUUID = uuid.uuid1().hex yield self.writeSession(SessionUUID, peerIP, hostIP) sid = self.db.runQuery("SELECT id FROM sessions WHERE sid = %s", (SessionUUID,)) yield sid @defer.inlineCallbacks def writeSession(self, SessionUUID, peerIP, hostIP): sensorname = self.getSensor() or hostIP r = yield self.db.runQuery("SELECT id FROM sensors WHERE ip = %s", (sensorname,)) if r: id = r[0][0] else: yield self.db.runQuery("INSERT INTO sensors (ip) VALUES (%s)", (sensorname,)) r = yield self.db.runQuery("""SELECT LAST_INSERT_ID()""") id = int(r[0][0]) self.simpleQuery( """ INSERT INTO sessions (sid, starttime, sensor, ip) VALUES (%s, FROM_UNIXTIME(%s), %s, %s) """, (SessionUUID, self.nowUnix(), id, peerIP)) </code></pre> <p>In short words: createSession creates an UUID for the session and calls writeSession to write this into my db. After this is written I try to select the ID of the last insert by using the UUID in the where statement and return the result.</p> <p>Now my problem. To update the session information I call this function:</p> <pre><code>def handleConnectionLost(self, sid, args): self.simpleQuery("UPDATE sessions SET endtime = now() WHERE sid = %s", (sid)) </code></pre> <p>As you can see I try to use the sid from createSession which is an Deferred object and not an integer. If I got this right and I add a Callback to <code>handleConnectionLost</code> it will run the query at this time so that I can use the value here. But this is not my only function where I need the sid. So it would be an overhead when I do every time a callback when I need the sid.</p> <ol> <li>Is there a way that I can give my sid as an integer to my functions? So that I'm just running the query one time? How does it have to look like?</li> <li>When I'm using a Deferred query with a <code>now()</code> statement. Will it use <code>now()</code> when I added this query to my Callbacks or will it use <code>now()</code> when the query is fired?</li> </ol>
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