On Mon, Aug 14, 2017 at 7:16 PM, Alvaro Herrera <alvhe...@2ndquadrant.com> wrote: >> Yeah, and the other question -- which Thomas asked before you >> originally committed originally, and which I just now asked again is >> "Why in the world are you using DSA for this at all?". There are >> serious problems with that which both he and I have pointed out, and >> you haven't explained why it's a good idea at any point, AFAICT. > > The main reason is that I envision that the workitem stuff will be used > for other things in the future than just brin summarization, and it > seemed a lame idea to just use a fixed-size memory area in the standard > autovacuum shared memory area. I think unbounded growth is of course > going to be bad. The current coding doesn't allow for any growth beyond > the initial fixed size, but it's easier to extend the system from the > current point rather than wholly changing shared memory usage pattern > while at it.
I don't accept that argument. All the current code does is allocate one fixed-size chunk of memory in DSA, so the whole pattern would have to be changed *anyway* if you wanted to grow the array. It's not like you are allocating the items one-by-one. I really, really strongly encourage you to rip the use of DSA out here entirely. It is reducing the reliability of a critical part of the system for no actual benefit other than speculation that this is going to be better in the future, and it adds a bunch of failure cases that we could just as well live without. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers