I don't remember it being an issue in the earlier version, but in 9.5 it could take anywhere from several seconds to several minutes to retrieve the column list after I click on the expand box at "Columns" in a tree. I saw a query like the following being executed during that time:
SELECT pc.table_column_name, pc.encoding_type, pc.access_rank FROM v_catalog.projections p INNER JOIN v_catalog.projection_columns pc ON ( p.projection_id = pc.projection_id) WHERE p.anchor_table_name = 'my_table'AND p.projection_schema = 'my_schema'
In my experience, queries that access system tables related to projections are often slow in a busy database, since those are optimized for write.
In comparison, the following query runs in 1-2 sec:
select table_name, column_name, data_type FROM v_catalog.columns where table_name='my_table' and table_schema='my_schema';
Thanks for the suggestion. We will look into this and see if we can use a different query.