RE: speeding up planning with partitions

Amit-san,

On Wed, Mar 6, 2019 at 5:38 AM, Amit Langote wrote:
...
> > I didn't investigate that problem, but there is another memory
> > increase
> issue, which is because of 0003 patch I think. I'll try to solve the latter
> issue.
> 
> Interested in details as it seems to be a separate problem.

I solved this problem.

I think we don't need to do list_copy in the below code.

+        /*
+         * No need to copy of the RTEs themselves, but do copy the List
+         * structure.
+         */
+        subroot->parse->rtable = list_copy(rtable_with_target);

Because subroot->parse->rtable will be copied again by:

         subroot->parse = (Query *)
             adjust_appendrel_attrs(parent_root,
-                                   (Node *) parent_parse,
+                                   (Node *) subroot->parse,
                                    1, &appinfo);

So I modified the code and did test to confirm memory increasement don't happen. The test and results are below.

[test]
* Create partitioned table with 1536 partitions.
* Execute "update rt set a = random();"

[results]
A backend uses below amount of memory in update transaction:

HEAD: 807MB
With v26-0001, 0002: 790MB
With v26-0001, 0002, 0003: 860MB
With v26-0003 modified: 790MB


I attached the diff of modification for v26-0003 patch which also contains some refactoring.
Please see if it is ok.
(Sorry it is modification for v26 patch though latest ones are v28.)

--
Yoshikazu Imai