[fdo-internals] Zero-length Data Properties

[Thomas Knoell]

Hi Jackie,

-1 is also returned when something is not supported. For example, if you ask for the maximum data value length for a BLOB/CLOB in SDF, -1 is returned because those types are not supported. And then there is the case that Trajan mentioned.

Maybe the -1 indicator is too overloaded with different contexts and may require some reviewing.

Thanks

  Thomas

-----Original Message-----
From: fdo-internals-bounces at lists.osgeo.org [mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Jackie C. Ng
Sent: Tuesday, September 02, 2008 11:05 AM
To: fdo-internals at lists.osgeo.org
Subject: RE: [fdo-internals] Zero-length Data Properties


Thomas,

But for something like SDF, even it returns -1 for string/BLOB/CLOB. It is a
fixed format with fixed specifications. What is the deal there?

- Jackie


Thomas Knoell wrote:
>
> Hi Jackie,
>
> The -1 is an indicator that the exact value cannot be determined. This is
> especially the case in ODBC that can connect to multiple data store
> sources, all with different limitations. Because the capability
> information is available before a connection is actually established more
> precise information cannot be provided.
>
> Thanks
>
>   Thomas
>
> -----Original Message-----
> From: fdo-internals-bounces at lists.osgeo.org
> [mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Jackie C. Ng
> Sent: Tuesday, September 02, 2008 4:47 AM
> To: fdo-internals at lists.osgeo.org
> Subject: [fdo-internals] Zero-length Data Properties
>
>
> Hi All,
>
> I have two related questions about Data Properties
>
> A) Why does FDO allow zero-length string/CLOB/BLOB data properties? In my
> feeble little mind, zero-length strings/CLOBs/BLOBs makes no sense
> whatsoever.
>
> B) I noticed that for some providers, the GetMaximumDataValueLength()
> method
> returns -1 for string/BLOB/CLOB properties. The same goes for
> GetMaximumDecimalPrecision() and GetMaximumPrecisionScale(). If I were to
> do
> something like this:
>
> ISchemaCapabilities capabilities;
> ...
> DataPropertyDefinition def = new DataPropertyDefinition("StringProp", "");
> def.Length =
> capabilities.GetMaximumDataValueLength(DataType.DataType_String);
>
> It would throw an exception because the Length property of
> DataPropertyDefinition can't be negative. So what should this value (-1)
> be
> interpreted as?
>
> - Jackie
>
> -----
> http://themapguyde.blogspot.com
>
> http://www.linkedin.com/in/jackieng
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-----
http://themapguyde.blogspot.com

http://www.linkedin.com/in/jackieng
--
View this message in context: http://www.nabble.com/Zero-length-Data-Properties-tp19266363p19271951.html
Sent from the FDO Internals mailing list archive at Nabble.com.

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