RE: Consider Parallelism While Planning For REFRESH MATERIALIZED VIEW

[Hou, Zhijie]

Hi

> Added this to commitfest, in case it is useful -
> https://commitfest.postgresql.org/31/2856/

I have an issue about the safety of enable parallel select.

I checked the [parallel insert into select] patch.
https://commitfest.postgresql.org/31/2844/
It seems parallel select is not allowed when target table is temporary table.

+       /*
+        * We can't support table modification in parallel-mode if it's a 
foreign
+        * table/partition (no FDW API for supporting parallel access) or a
+        * temporary table.
+        */
+       if (rel->rd_rel->relkind == RELKIND_FOREIGN_TABLE ||
+               RelationUsesLocalBuffers(rel))
+       {
+               table_close(rel, lockmode);
+               context->max_hazard = PROPARALLEL_UNSAFE;
+               return context->max_hazard;
+       }

For Refresh MatView.
if CONCURRENTLY is specified, It will builds new data in temp tablespace:
        if (concurrent)
        {
                tableSpace = GetDefaultTablespace(RELPERSISTENCE_TEMP, false);
                relpersistence = RELPERSISTENCE_TEMP;
        }

For the above case, should we still consider parallelism ?

Best regards,
houzj