On 2019/03/20 9:49, Robert Haas wrote:
> On Fri, Mar 8, 2019 at 4:18 AM Amit Langote
> <Langote_Amit_f8@lab.ntt.co.jp> wrote:
>> Maybe you know that range_table_mutator() spends quite a long time if
>> there are many target children, but I realized there's no need for
>> range_table_mutator() to copy/mutate child target RTEs. First, there's
>> nothing to translate in their case. Second, copying them is not necessary
>> too, because they're not modified across different planning cycles. If we
>> pass to adjust_appendrel_attrs only the RTEs in the original range table
>> (that is, before any child target RTEs were added), then
>> range_table_mutator() has to do significantly less work and allocates lot
>> less memory than before. I've broken this change into its own patch; see
>> patch 0004.
>
> Was just glancing over 0001:
>
> - * every non-join RTE that is used in the query. Therefore, this routine
> - * is the only place that should call build_simple_rel with reloptkind
> - * RELOPT_BASEREL. (Note: build_simple_rel recurses internally to build
> - * "other rel" RelOptInfos for the members of any appendrels we find here.)
> + * every non-join RTE that is specified in the query. Therefore, this
> + * routine is the only place that should call build_simple_rel with
> + * reloptkind RELOPT_BASEREL. (Note: "other rel" RelOptInfos for the
> + * members of any appendrels we find here are built later when query_planner
> + * calls add_other_rels_to_query().)
>
> Used -> specified doesn't seem to change the meaning, so I'm not sure
> what the motivation is there.
Well, I thought it would clarify that now add_base_rels_to_query() only
adds "baserel" RelOptInfos, that is, those for the relations that are
directly mentioned in the query.
Maybe:
...that is mentioned in the query.
or
...that is directly mentioned in the query.
?
Thanks,
Amit
