Parallel Btree index scan

Hi All, Can you please help me to understand what is parallel btree index scan in Postgres 10. And what is the difference between index scan and index only scan. Thanks, Krithika

Parallel Query

Hi All, I was reading about parallel queries in postgresql 10. I came across the property max_parallel_workers_per_gather. It sets the maximum number of workers that can be started by a single Gather or Gather Merge node. I am not able to understand gather and gather merge node. What is the dif