Bruce, You can take a look at the GDAL/OGR's Oracle driver code at http://trac.osgeo.org/gdal/browser/branches/1.6/gdal/ogr/ogrsf_frmts/oci Take a look at the implementation of the function at http://trac.osgeo.org/gdal/browser/branches/1.6/gdal/ogr/ogrsf_frmts/oci/ogrocitablelayer.cpp#L1189
Unless you are using a filter for that layer, it is executing another SQL command. On Thu, Oct 15, 2009 at 1:12 AM, Clay, Bruce <[email protected]> wrote: > Chaitany: > > > > Thanks for your reply. > > > > I would expect to get one delay due to the connection time but I did not > expect one for both the GetFeatureCount and the GetNextFeature. Both of > those calls are on the same layer variable. I originally had the > GetFeatureCount before the ResetReading. That gave the same delay. As it > turned out the code show below actually had 3 delays. One for the > GetNextFeature outside the loop, one for the GetFeatureCount and another one > for the first encounter of the GetNextFeature at the bottom of the loop. > Apparently the GetFeatureCount is leaving the feature pointer at the bottom > of the loop and we have to take time to move back to the top. > > > > I would step into the code but I can’t get Visual Studio to dig down into > gdal16.dll for some reason even though it was built as a debug library. > > > > > > Bruce > ------------------------------ > > *From:* Chaitanya kumar CH [mailto:[email protected]] > *Sent:* Wednesday, October 14, 2009 2:34 PM > *To:* Clay, Bruce > *Cc:* [email protected] > *Subject:* Re: [gdal-dev] double delay getting feature count > > > > Bruce, > > The GetFeatureCount function gets the value with an SQL query to the data > server. The bottleneck may be at the connection. > > On Wed, Oct 14, 2009 at 9:28 PM, Clay, Bruce <[email protected]> wrote: > > I have tried several different arrangements trying to get the feature count > from a user selection and I am getting a delay two times for each query. > > > > My current arrangement is > > > > OGRLayer *queryLayer = dataSource->ExecuteSQL(fullQueryString, NULL, > "generic"); > > > > if (queryLayer != NULL) > > { > > queryLayer->ResetReading(); > > OGRFeature *feature = queryLayer->GetNextFeature(); > > > > int numFeatures = queryLayer->GetFeatureCount(); > > > > . . .Display progress meter then loop reading the features from Oracle > > > > > > > > > > I have tried putting the call to GetFeatureCount first and there is no > apparent difference. > > > > I am reading data from an Oracle database and using GDAL version 1.6.2 on > Windows XP > > > > The call to ExecuteSql returns right away but the call to the first > GetNextFeature and the call to GetFeatureCount both have a long delay > depending on the size of the dataset. > > > > I need the feature count to use in a progress popup window to let the user > know what is happening. > > > > Is there a way to only pay for the query time once and still get the > feature count? > > > > > > Bruce > > This message and any enclosures are intended only for the addressee. Please > > notify the sender by email if you are not the intended recipient. If you are > > not the intended recipient, you may not use, copy, disclose, or distribute > this > > message or its contents or enclosures to any other person and any such actions > > may be unlawful. Ball reserves the right to monitor and review all messages > > and enclosures sent to or from this email address. > > > _______________________________________________ > gdal-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/gdal-dev > > > > > -- > Best regards, > Chaitanya kumar CH. > > This message and any enclosures are intended only for the addressee. Please > notify the sender by email if you are not the intended recipient. If you are > not the intended recipient, you may not use, copy, disclose, or distribute > this > message or its contents or enclosures to any other person and any such actions > may be unlawful. Ball reserves the right to monitor and review all messages > and enclosures sent to or from this email address. > > -- Best regards, Chaitanya kumar CH.
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