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Must these be identical? Providers are not required to support the same syntax than QgsExpression. Some might use similar syntax, but aren't required to match the functionality of QgsExpression (some might only support a subset (eg. OGR on shapes), some a superset (PostgreSQL) and some anything in between). So the help in the expression builder is inaccurate and misleading and the interactive expression evaluation won't work there either.

Jürgen Fischer wrote:

Must these be identical? Providers are not required to support the same syntax than QgsExpression. Some might use similar syntax, but aren't required to match the functionality of QgsExpression (some might only support a subset (eg. OGR on shapes), some a superset (PostgreSQL) and some anything in between). So the help in the expression builder is inaccurate and misleading and the interactive expression evaluation won't work there either.

so maybe would be better to replace the query builder in the WFS client with the one available now in the vector properties?

Giovanni Manghi wrote:

Jürgen Fischer wrote:

Must these be identical? Providers are not required to support the same syntax than QgsExpression. Some might use similar syntax, but aren't required to match the functionality of QgsExpression (some might only support a subset (eg. OGR on shapes), some a superset (PostgreSQL) and some anything in between). So the help in the expression builder is inaccurate and misleading and the interactive expression evaluation won't work there either.

so maybe would be better to replace the query builder in the WFS client with the one available now in the vector properties?

or not, I remember that someone was working on adding spatial operators to the expression builder to allow use spatial relations to build queries. I guess it needs the new expression builder.

Well... you devs known what is the right thing to do.

Giovanni Manghi wrote:

or not, I remember that someone was working on adding spatial operators to the expression builder to allow use spatial relations to build queries. I guess it needs the new expression builder.

yes, the wfs client maps QgsExpressions to the OGC filter syntax - so using the expression builder is the right choice.

Jürgen Fischer wrote:

Giovanni Manghi wrote:

or not, I remember that someone was working on adding spatial operators to the expression builder to allow use spatial relations to build queries. I guess it needs the new expression builder.

yes, the wfs client maps QgsExpressions to the OGC filter syntax - so using the expression builder is the right choice.

If I'm not wrong the developer (rené-luc) was thinking to add this feature also the expression builder in the vector properties, not only in the wfs client, but I'm not sure now.

Jürgen Fischer wrote:

Must these be identical? Providers are not required to support the same syntax than QgsExpression. Some might use similar syntax, but aren't required to match the functionality of QgsExpression (some might only support a subset (eg. OGR on shapes), some a superset (PostgreSQL) and some anything in between). So the help in the expression builder is inaccurate and misleading and the interactive expression evaluation won't work there either.

I agree this is the main issue. Something that I have considered is decoupling the expression builder from QgsExpression and allowing it to take just a set of functions in a given format. This would allow us to pass provider functions into the UI and have them listed like they currently are.

The expression builder (with the new spatial function) it is now available in the table of attributes for selections, I guess that it makes even more sense now to have it also to filter features in the query builder.

@Giovanni not a simple task as they are different things. The attribute table is using QgsExpression while the Filter/Query option on the layer is using the providers syntax. In order to support this QgsExpressionBuilder would need to be expanded to support plugable expression engines so that we could pass it a list of functions for the different providers.

I can be done but it would take a bit of effort as you would have to build up a list of functions for each provider.