[Twisted-Python] adbapi and multiple queries in single

[Vishal Shetye]

Phil thanks for the reply. I plan to do something similar.
[sorry for not providing code snippet.]
I have modified your code (please ignore queries and other errors)
However I am not very much convinced with this approach,
As you can see validate of ObjectGateway is a public method which also needs to be called from handleLogin.
So I have to write two methods one public 'validate' and other private '_validate'.
Any comments/suggestions or pointers to any existing applications/architecture documents with similar data access?

class TableGateway(object):
     def _getUserName(self, trans, user_id):
         result = trans.execute('SELECT username FROM user WHERE id =
%s', user_id)
         return result[0][0]

     def _sessionUpdateQuery(self, trans, sid, username):
         trans.execute('UPDATE session SET username = %s WHERE sid =
%s', [username, sid])

     def validateSid(self, txn, sid):
          res = txn.execute('select id from user where id=?', (sid,))
          return True if res else False

class ObjectGateway(object):
     def __init__(self, pool):
         self.pool = pool
         self.tblGw = TableGateway()

     def _validate(self, txn, sid):
          return self.tblGw.validateSid(txn, sid)

     def validate(self, sid):
          return self.pool.runInteraction(self._validate, sid)

     def handleLogin(self, sid, user_id):
         def _loginInteraction(trans):
             if not self._validate(trans, sid):
                 raise "invalid sid"
             u = self.tblGw._getUserName(trans, user_id)
             self.tblGw._sessionUpdateQuery(trans, sid, username)
             return u
         return self.pool.runInteraction(_loginInteraction)

Regards,
vishal

Date: Tue, 23 Jun 2009 10:25:16 -0400
From: Phil Christensen <phil at bubblehouse.org>
Subject: Re: [Twisted-Python] adbapi and multiple queries in single
        transaction.
To: Twisted general discussion <twisted-python at twistedmatrix.com>
Message-ID: <2E70F4C7-5253-44B2-9DB8-79D8817E96F4 at bubblehouse.org>
Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes

On Jun 23, 2009, at 9:45 AM, Vishal Shetye wrote:
>> I initially thought of putting all the queries per operation in a
>> runInteraction. However this results in code-duplication as many
>> queries are shared between different operations.

>It seems like the easiest way to deal with this would be to make
>'private' methods for all the standard queries; these methods/
>functions would accept a transaction object like you said, but the
>methods themselves would only be called from an interaction, which can
>supply the transaction object.

>Then in each public ObjectGateway method you can just define an inner
>function to serve as the interaction, calling each private query
>method in turn, using the transaction object provided to that
>interaction.

>Here's a stupidly trivial example:

class ObjectGateway(object):
     def __init__(self, pool):
         self.pool = pool

     def _getUserName(self, trans, user_id):
         result = trans.execute('SELECT username FROM user WHERE id =
%s', user_id);
         return result[0][0]

     def _sessionUpdateQuery(self, trans, sid, username):
         trans.execute('UPDATE session SET username = %s WHERE sid =
%s', [username, sid]);

     def handleLogin(self, sid, user_id):
         def _loginInteraction(trans):
             u = self._getUserName(trans, user_id)
             self._sessionUpdateQuery(trans, sid, username)
             return u
         return self.pool.runInteraction(_loginInteraction)

>Other than being careful not to mess around with the instance state
>during those interactions (they are running in a thread, after all),
>this should be pretty straightforward.

>Hope this helps,

-phil
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