[Qgis-developer] QgsDataProvider and supportsSubsetString

[Chris Crook]

Hi All

As we are looking at API tidy ups (I understand), would there be any support for providing a bit more granularity in supportsSubsetString.  At the moment this is a simple boolean, and the GUI offers a SQL based subset string builder.

However not all providers naturally use SQL based strings.  I'm interested in adding subset capability to the delimited text provider, whichi I've done using QgsExpression as the basis for subsets.  This works very well except that the GUI isn't an expression builder.  I think there may be similar issues with the WFS provider.

What I am proposing is something more like an enum QgsDataProvider::SubsetStringType, which could then be interrogated by the properties dialog to select the appropriate query builder dialog.

Logically this would supplant the supportsSubsetString boolean which could be deprecated, replaced with

virtual QgsDataProvider::SubsetStringType QgsDataProvider::subsetStringType(){ return NoSubsetString; }

Other types could be SqlSubsetString, ExpressionSubsetString, ...?

Thoughts anyone?

Thanks
Chris

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