Using QGIS Expressions in any datasource URI

[cxcandid]

Feature description

Maybe I miss a point here, but wouldn't it be nice if we could use QGIS Expressions in any datasource URI (even PostGIS)?

At the moment we can only use QGIS Expression Functions in virtual layers (i.e. SELECT * FROM mylayer WHERE name LIKE(var('filter')))

Would it cost to much processing time to parse the datasource string every time before rendering.
I'm thinking about having something like that:

SELECT * FROM mylayer WHERE name LIKE([% @filter %])

Can someone explain why this is not possible?

Additional context

No response

[elpaso]

Do you mean something like https://plugins.qgis.org/plugins/qgis-subset-expression-plugin/ ?

[cxcandid]

@elpaso cool plugin, thanks! ... In principle, it does what I want to achieve, but unfortunately only with filters (which my bad example also shows).

In truth, it's about more than that:

SELECT * FROM mypgfunction([% @myid %])

[cxcandid]

@elpaso your plugin is a very good starting point... didn't know that we can implement a handler for the customVariablesChanged signal in PyQGIS.

So, let's implement (Python) Expressions in QGIS variables! 😁😅

[elpaso]

Sounds good, feel free to add the functionality to the qgis-subset-expression-plugin/ if you feel like to.