I try to open big PostGIS table in QGIS, with 500+M rows. I zoom in to small area, and limit zooms, so the query response is expected to be reasonably small. Tested this also directly in DB. The table has indexes, so I can see that raw query is fast. The table has already unique index for two fields ("partition","partition_offset")

Problem: When I add the table as layer, then QGIS hangs. I see in DB a long running query: SELECT count(distinct ("partition","partition_offset"))=count(("partition","partition_offset")) FROM "public"."mytable_geo" and from query planner I see that this does full scan to table, which takes possibly hours in my case. It looks like that QGIS wants to be really sure that my "unique" constraint makes the values really unique. Is there a way to avoid it?

QGIS version: 3.6.1-Noosa