How to read query plans

You can view a query plan using the EXPLAIN (ANALYZE, VERBOSE, BUFFERS) command. The plan is organized as a tree, where each node has these details:

• operation e.g. Index Scan, Group Aggregate, Sort
• cost=startup cost..total cost → The startup is the time before retrieval of data and includes scanning of indexes, joins of tables, organizing additional parallel workers
• rows=N → estimated number of rows retrieved by the node
• width=W → estimated avg. size of rows produced by the node, in bytes
• buffers → number of pages read from cache (hit) and from disk (read)