On 26 November 2015 at 03:41, Robert Haas <robertmh...@gmail.com> wrote:
> Attached find a patch that does (mostly) two things. First, it allows > the optimizer to generate plans where a Nested Loop or Hash Join > appears below a Gather node. This is a big improvement on what we > have today, where only a sequential scan can be parallelized; with > this patch, entire join problems can be parallelized, as long as they > don't need a Merge Join (see below for more on this). Sounds like good progress. This gives us multiple copies of the hash table, which means we must either use N * work_mem, or we must limit the hash table to work_mem / N per partial plan. How can the partial paths share a hash table? -- Simon Riggs http://www.2ndQuadrant.com/ <http://www.2ndquadrant.com/> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
