Horiguchi-san, Thanks for the comment. My reply is a bit late now, but....
On Wed, Jul 10, 2019 at 5:39 PM Kyotaro Horiguchi <horikyota....@gmail.com> wrote: > At Wed, 10 Jul 2019 16:35:18 +0900, Amit Langote <amitlangot...@gmail.com> > wrote: > - * Switch to appropriate context for constructing querytrees (again, > - * these must outlive the execution context). > + * Switch to appropriate context for constructing query and plan trees > + * (again, these must outlive the execution context). Normally, it's > + * MessageContext, but if there are more queries to plan, we use a > + * temporary child context that will be reset after executing this > + * query. We avoid that overhead of setting up a separate context > + * for the common case of having just a single query. > > Might be stupid, but I feel uneasy that "usually it must live in > MessageContxt, but not necessarily if there is succeeding > query".. *I* need more explanation why it is safe to use that > short-lived context. So the problem we're trying solve with this is that memory consumed when parsing/planning individual statements pile up in a single context (currently, MessageContext), which can lead to severe bloat especially if the planning of individual statements consumes huge amount of memory. The solution is to use a sub-context of MessageContext for each statement that's reset when its execution is finished. I think it's safe to use a shorter-lived context for each statement because the memory of a given statement should not need to be referenced when its execution finishes. Do you see any problem with that assumption? Thanks, Amit
