Re: Parallel Bitmap Heap Scan reports per-worker stats in EXPLAIN ANALYZE

 

Hi David,

According to the docs[1]: "In a parallel bitmap heap scan, one process is chosen as the leader. That process performs a scan of one or more indexes and builds a bitmap indicating which table blocks need to be visited. These blocks are then divided among the cooperating processes as in a parallel sequential scan."

My understanding is that the "Heap Blocks" statistic is only reporting blocks for the bitmap (i.e. not the subsequent scan). As such, I think it is correct that the workers do not report additional exact heap blocks. 

 

In your example, if you add the buffers and verbose parameters, do the worker reported buffers numbers report what you are looking for?

i.e. explain (analyze, buffers, verbose, costs off, timing off) select * from foo where col0 > 900 or col1 = 1;