Improved PostgreSQL loading speed by adjusting table structure, tuning config, disabling full page writes & removing constraints/indexes. Used unlogged tables & \copy command to load data from CSV file in 35.41s.

Recursive CTEs use `WITH RECURSIVE` clause to define recursive query, adjacency lists store each node's children separately & use joins, nested sets store ancestors/descendants in separate table & use range queries.

Optimize PostgreSQL query performance: Increase stats collection, adjust `random_page_cost` & understand query planner decisions to boost large table queries!

Optimizing PostgreSQL queries: Use loose index-only scans for efficient retrieval of recent records, but weigh the trade-offs with increased indexing overhead.