[fdo-internals] Zero-length Data Properties

Thomas Knoell thomas.knoell at autodesk.com
Tue Sep 2 09:32:36 EDT 2008

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.



-----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

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 =

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


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