QGIS » QGIS Application

Apologies if I've put this into the wrong category, this is my first time posting a bug report.

I have a large dataset with more than 3 billion points. When constructing a sql expression in the Set Filter of layer properties and using the 'Sample' feature, QGIS 2.8 goes non-responsive. The field I'm sampling is of type integer.

Upon looking at the PostGIS server status, I can see that the query sent by QGIS is the following:

SELECT DISTINCT "field_to_sample"::text FROM "public"."feature_dataset" ORDER BY "field_to_sample" LIMIT 25

Within PostGIS, changing this to the actual datatype of the dataset returns a result in a little under 2 seconds;

SELECT DISTINCT "field_to_sample"::integer FROM "public"."feature_dataset" ORDER BY "field_to_sample" LIMIT 25

I imagine that the type conversion to text of large datasets (if that is what is happening?) could be causing the non-responsive behaviour within QGIS. Does the type conversion have to happen within the query?

QGIS Version 2.6 does not do this type conversion, so therefore returns the expected result within a few seconds.

Cheers,

Pete