Hi

In my test(PG9.3.4), i found when update a parent table which has a large 
number of child tables, the execute plan will consume lots of memory. And 
possibly cause OOM.


For example:
 create table maintb(id int,name char(10));
 create table childtb_1 (CHECK ( id BETWEEN 1 AND 200)) inherits(maintb);
 create table childtb_2 (CHECK ( id BETWEEN 201 AND 400)) inherits(maintb);
 ...
 create table childtb_n ...




When there are 100 child tables,the following update statement will consume 
about 8MB memory when invoking pg_plan_queries()
update maintb set name = 'aaaaa12345' where id=1;


And, when there are 1000 child tables,the same update statement will consume 
717MB memory when invoking pg_plan_queries().


Does this a known problem, and could that be improved in the future?


BTW:
The following comment is according my debuging when update the parent table 
with 1000 child tables
src/backend/optimizer/plan/planner.c
static Plan *
inheritance_planner(PlannerInfo *root)
{
...
    foreach(lc, root->append_rel_list)//### loop 1001 time
    {
...
        subroot.parse = (Query *)
            adjust_appendrel_attrs(root,
                                 (Node *) parse,
                                 appinfo);//### allocate about 300KB memory a 
time.


...
        subroot.append_rel_list = (List *) 
copyObject(root->append_rel_list);//### allocate about 400KB memory a time.


...
    }
...
}


Best Regards
Chen Huajun

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