Re: create_unique_path and GEQO

On Wed, Mar 22, 2017 at 3:43 PM, Ashutosh Bapat
<ashutosh(dot)bapat(at)enterprisedb(dot)com> wrote:
> Hi,
> In create_unique_path() there's comment
> /*
> * We must ensure path struct and subsidiary data are allocated in main
> * planning context; otherwise GEQO memory management causes trouble.
> */
> oldcontext = MemoryContextSwitchTo(root->planner_cxt);
>
> pathnode = makeNode(UniquePath);
>
> This means that when GEQO resets the memory context, the RelOptInfo
> for which this path is created and may be set to cheapest_unique_path
> goes away, the unique path lingers on in the planner context.
> Shouldn't we instead allocate the path in the same context as the
> RelOptInfo similar to mark_dummy_rel()?
>

tried this change as attached patch. I ran make installcheck with
geqo_threshold = 2. Only join.sql failed several plans changed, which
is expected. There was one difference related to changed output order
but that's because of the changed plan.

Adding this to the commitfest.

--
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company