FreeTDS Development Group

["Thompson, Bill D (London)" <bill_d_thompson AT ml.com>]

Shaun,

> what i mean is i dont get a chance to call the 
> following functions after the 'return NO_MORE_ROWS'
> dbfreebuf(dbconn);
> dbclose(dbconn);
> dbexit();

So. this implies that you are all done after finding your single match.
does that mean your program terminates ? or does it keep going, leaving
the connection bound to "dbconn" hanging around ?

If the program is really finished at this point, then the server would
clean up the connection from it's point of view.
After all, that would be just like a process abending mid-stream.
Inelegant, but I can't see any real issues with it.

If your program isn't finished at this point, then  you can't possibly
be doing anything else on the connection bound to "dbconn", unless you
run a dbcancel() or dbcanquery() first. So I guess it would just hang
around until the program eventually terminates.
Again, from the server's point of view, this would just look like an
unexpected process termination, and it should clean up.

I take it that your "InsertRecord" function uses a separate connection
to the one bound to "dbconn".
You would definitely run into the problems previously discussed
otherwise.

> I just want to be sure that for some reason all 
> the records in my table aren't being searched 
> when i exit as this would slow my programs down.

Well, I suppose a dbcanquery() *would* read through all the records, 
so in the context of your design it would be a bad thing to call it.
That doesn't mean I think this is a good program design, though...
Do you potentially return 2.4 million records in this resultset ? 
If so, you should really think again about how to achieve your ends.

How complex is the calculation in LatLonDistance ?
where have prev_lat, prev_lon and SweepRadius come from ?

HTH,

Bill



-----Original Message-----
From: freetds-bounces AT lists.ibiblio.org
[mailto:freetds-bounces AT lists.ibiblio.org] On Behalf Of craigs
Sent: 10 March 2005 13:10
To: FreeTDS Development Group
Subject: Re: [freetds] dbnextrow() question


Bill,

'return NO_MORE_ROWS' does take me out of the code segment which is 
exactly what i want, but is it safe to do so.  I know that the insert 
just before i call the return statement also works.  I just want to be 
sure that for some reason all the records in my table aren't being 
searched when i exit as this would slow my programs down, what i mean is

i dont get a chance to call the following functions after the 'return 
NO_MORE_ROWS'

dbfreebuf(dbconn);
dbclose(dbconn);
dbexit();

Would this have any effect on my number of licences seen as its not 
closing the connection, any other side-effects?

Shaun.

Thompson, Bill D (London) wrote:

>Shaun,
>
>that "return NO_MORE_ROWS" is going to leap right out of this entire
>code segment, n'est-ce pas ?
>..in which case you'll only call the dbcanquery() after dbnextrow() has
>returned NO_MORE_ROWS
>..at which point there's no point in calling dbcanquery()
>
>did you mean to code a "break" instead of the "return NO_MORE_ROWS" ?
>
>Also, your table has 2.4 million rows.
>does that mean the query behind this dbresults loop is returning 2.4
>million rows ?
>if so, you should try and cut that number down at source, via your
>query.
>..unless you have a nice fat network :-)
>
>Bill
>
>-----Original Message-----
>From: freetds-bounces AT lists.ibiblio.org
>[mailto:freetds-bounces AT lists.ibiblio.org] On Behalf Of craigs
>Sent: 10 March 2005 12:03
>To: FreeTDS Development Group
>Subject: Re: [freetds] dbnextrow() question
>
>
>Right having problems with this, i want to exit query when i get what i

>want, theres over 2.4 millions records in my table so really need to
get
>
>this right, can someone advise me if the following code would work.
>
>while ((return_code = dbresults(dbconn)) != NO_MORE_RESULTS)
>{
>             if (return_code == SUCCEED)
>             {
>                        /* Bind results to program variables. */
>                        dbbind(dbconn, 1, NTBSTRINGBIND, 0, (BYTE *)& 
>PlaceName);
>                        dbbind(dbconn, 2, FLT8BIND, 0,
>(BYTE*)&Longitude);
>                        dbbind(dbconn, 3, FLT8BIND, 0,
>(BYTE*)&Latitude);
>                        dbbind(dbconn, 4, NTBSTRINGBIND, 0, (BYTE *)& 
>Country);
>                        dbbind(dbconn, 5, NTBSTRINGBIND, 0, (BYTE *)&
>Town);
>                        dbbind(dbconn, 6, INTBIND, (DBINT)0, (BYTE *)& 
>SweepRadius);
>           
>                        /* Retrieve and print the result rows. */
>                        while (dbnextrow(dbconn) != NO_MORE_ROWS)
>                        {
>                                    tempDist = LatLonDistance(
prev_lat,
>
>prev_lon, Latitude, Longitude );
>               
>                                    tempDist = tempDist * 1000; 
>//convert kilometers to meters
>               
>                                    if ( tempDist <= SweepRadius )
>                                    {
>                                            /* Find what i'm looking
for
>
>so i call a function to Insert into a table using variables above. */
>                                            InsertRecord(roadsquery);
>                  
>                                            return NO_MORE_ROWS;
>                                    }
>                        }
>                        dbcanquery(dbconn);
>             }
>}
>
>Any help would be much appreciated, thanks.
>
>Shaun.
>
>craigs wrote:
>
>  
>
>>can i do the following using dbcanquery()
>>
>>while (dbnextrow(dbconn) != NO_MORE_ROWS)
>>{
>>    bind results to varialbes
>>
>>         if ( find what i want )
>>         {
>>              do something here
>>               now exit doing the following
>>
>>            dbcanquery(dbconn);
>>         }
>>}
>>
>>will this let me exit the loop correctly with the variables still set?
>>
>>
>>
>>Thompson, Bill D (London) wrote:
>>
>>    
>>
>>>Easy, cowboy.
>>>
>>>well, *might* is right , if you'll excuse the pun - as there is one
>>>circumstance when it wouldn't go wrong.
>>>
>>>On the other hand, I *might* not have had the time to go into all the
>>>gory details :-)
>>>
>>>Yours non-specifically,
>>>
>>>Bill
>>>
>>>-----Original Message-----
>>>From: freetds-bounces AT lists.ibiblio.org
>>>[mailto:freetds-bounces AT lists.ibiblio.org] On Behalf Of Lowden, James
>>>      
>>>
>K
>  
>
>>>Sent: 08 March 2005 17:57
>>>To: ml AT freetds.org
>>>Subject: RE: [freetds] dbnextrow() question
>>>
>>>
>>> 
>>>
>>>      
>>>
>>>>From: Thompson, Bill D (London)
>>>>Sent: Tuesday, March 08, 2005 6:01 AM
>>>>
>>>>your next call to dblibrary *might* fail with a "results pending"
>>>>        
>>>>
>type
>  
>
>>>>error though, if you tray and do another operation on the same
>>>>        
>>>>
>channel
>  
>
>>>>  
>>>>        
>>>>
>>>What "might"?  *Will* fail, period. 
>>>The code below doesn't tell the server to stop sending rows, and
>>>      
>>>
>doesn't
>  
>
>>>tell the library the that the result set was exhausted/cancelled.
>>>db-lib maintains information about the state of the connection, and
>>>      
>>>
>will
>  
>
>>>refuse to send another query.  Anything else is a bug. 
>>>The only exception would be if the last row fetched happened also to
>>>      
>>>
>be
>  
>
>>>the last row sent, i.e., the last row of the result set.  Some
>>>implementations of db-lib (not FreeTDS, afaik), will note the
>>>end-of-rowset packet and update the internal connection status
>>>automatically.  Others will not do so until dbnextrow returns
>>>NO_MORE_ROWS. 
>>>Am I missing something? 
>>>--jkl
>>>
>>>
>>> 
>>>
>>>      
>>>
>>>>-----Original Message-----
>>>>From: freetds-bounces AT lists.ibiblio.org
>>>>[mailto:freetds-bounces AT lists.ibiblio.org] On Behalf Of craigs
>>>>Sent: 08 March 2005 10:58
>>>>To: FreeTDS Development Group
>>>>Subject: Re: [freetds] dbnextrow() question
>>>>
>>>>
>>>>found an easier way of doin it.
>>>>
>>>>while (dbnextrow(dbconn) != NO_MORE_ROWS)
>>>>{
>>>>     if ( find what i want )
>>>>     {
>>>>           do something here
>>>>           now exit doing the following
>>>>
>>>>        return NO_MORE_ROWS; // this will let you exit
>>>>     }
>>>>}
>>>>
>>>>
>>>>Thompson, Bill D (London) wrote:
>>>>
>>>>  
>>>>
>>>>        
>>>>
>>>>>Shaun
>>>>>
>>>>>see dbcanquery() or dbcancel() . dbcanquery looks like exactly what
>>>>>    
>>>>>          
>>>>>
>>>you
>>> 
>>>
>>>      
>>>
>>>>>want.
>>>>>
>>>>>-----Original Message-----
>>>>>From: freetds-bounces AT lists.ibiblio.org
>>>>>[mailto:freetds-bounces AT lists.ibiblio.org] On Behalf Of craigs
>>>>>Sent: 04 March 2005 12:19
>>>>>To: FreeTDS Development Group
>>>>>Subject: [freetds] dbnextrow() question
>>>>>
>>>>>
>>>>>Could someone tell me how to exit this loop?  I dont want to run
>>>>>    
>>>>>          
>>>>>
>>>>through
>>>>  
>>>>
>>>>        
>>>>
>>>>>thousands of unnecessary records when i find the one i want.
>>>>>
>>>>>while (dbnextrow(dbconn) != NO_MORE_ROWS)
>>>>>{
>>>>>    if ( find what i want )
>>>>>    {
>>>>>          do something here
>>>>>          now i want to exit out off this loop
>>>>>    }
>>>>>}
>>>>>
>>>>>Shaun
>>>>>    
>>>>>          
>>>>>
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