RisingWave Community - Why does indexing a field of a materialized view not improve query performance?

Indexing a field of a materialized view may not always improve query performance, as seen in the example provided.
The query performance results showed that adding an index on ad_id did not significantly improve the query execution time.
The query cost for the indexed materialized view and the non-indexed materialized view was similar.
The issue may be related to filter push down not being implemented, leading to full table scans even with indexing.
The slow query performance could be due to the lack of optimization for limit and offset operations in the scan process.
Implementing features like partition pruning and parallel table scan may help improve query performance in materialized views.