[fdo-internals] Use of SQL pass through

[Orest Halustchak]

Hi,

But the class definition includes additional information that you wouldn't find just by getting information a property at a time. The idea with the feature reader is that it is returning "objects" based on a class definition rather than arbitrary collections of columns. The addition of getting a feature reader from the SQL command is intended to be optional for the caller, they don't need to use it if they don't want. But the class definition includes extra information such as the identity properties (primary key) so that the caller can determine the unique identity of these objects, which is important if the caller is going to draw these objects and then enable a user to edit them or go back to the data store for other information about the object.

Thanks,
Orest.

From: fdo-internals-bounces at lists.osgeo.org [mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Haris Kurtagic
Sent: Thursday, June 25, 2009 10:10 AM
To: FDO Internals Mail List
Subject: RE: [fdo-internals] Use of SQL pass through

Hi,

To return FDO class from any SQL will require extra processing from provider. This processing will in best case add unnecessary overhead to provider.
My suggestion is to enable application to get info about returned columns trough feature readers. Same way as non-fdo applications are doing it right now.
I don't see any advantage in trying to squeeze SQL statement result into FDO class and I can see many problems there.

Even opposite, I would prefer to optimize FDO commands. Instead trying to guess what type of SLQ statement application has executed or parsing current FDO filters it would be better that we would have very simple "query window of data" type of command in FDO. That is something not directly related to this RFC but it is direction where I think FDO could go. Less overhead and simpler commands for most usual  tasks.

Haris

From: fdo-internals-bounces at lists.osgeo.org [mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Orest Halustchak
Sent: Thursday, June 25, 2009 3:17 PM
To: FDO Internals Mail List
Subject: RE: [fdo-internals] Use of SQL pass through

Hi,

There hasn't been too much feedback on this.

Haris, for SQL selects, to return data in a feature reader, we either can simply describe the results of the select and produce a temporary fdo class for the reader or if the SQL select happens to correspond cleanly to an existing feature class (e.g. something as simple as select * from roads), then we can use that fdo class instead. The goal is to make it easier for application developers that can use either fdo selects or sql selects and process the results with a common reader.

Anybody else have comments? I know we got some feedback from Jackie.

Thanks,
Orest.


From: fdo-internals-bounces at lists.osgeo.org [mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Greg Boone
Sent: Thursday, June 04, 2009 11:39 AM
To: FDO Internals Mail List
Subject: RE: [fdo-internals] Use of SQL pass through

Hi Haris,

Can you provide some examples of non-DDL use cases that would make the proposal too complex? I also feel we should limit the discussion at this time to read only DML statements such as Select.

Greg

From: fdo-internals-bounces at lists.osgeo.org [mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Haris Kurtagic
Sent: Thursday, June 04, 2009 5:41 AM
To: FDO Internals Mail List
Subject: RE: [fdo-internals] Use of SQL pass through

I would like to divide this and answer in two parts.

Part with Parameters direction is something we need. As it is already written , mostly to be able to execute and get results from stored procedures.

About executing SQL statements and trying to squeeze result of it inside FDO class/schema, I think it is too complex and in my mind without chance to be successful. There is so many cases in which it can't be done properly. If we are missing some info about result of execution of SQL we could look into existing specs like ODBC and add those. I agree FDO application should be able to get all necessary info about executed SQL so app can be written in generic way but I don't see putting that info in FDO class or reengineering sql etc.. I believe what can be done with api's like odbc is ok for fdo api too.

Haris

From: fdo-internals-bounces at lists.osgeo.org [mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Orest Halustchak
Sent: Wednesday, June 03, 2009 3:28 PM
To: FDO Internals Mail List
Subject: [fdo-internals] Use of SQL pass through

Hi,

I would like to solicit feedback, discussion, and suggestions on requirements and issues that we are seeing with the FdoISQLCommand which is used for the purpose of SQL pass through for some of the RDBMS-based providers.

Please see the discussion below.

Thanks,
Orest.

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