Re: Push down more full joins in postgres_fdw

On Mon, Sep 26, 2016 at 1:05 PM, Etsuro Fujita
<fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> On 2016/09/15 15:29, Ashutosh Bapat wrote:
>>
>> On Wed, Sep 14, 2016 at 8:52 PM, Robert Haas <robertmhaas(at)gmail(dot)com>
>> wrote:
>
>
>>> I'm not sure why it wouldn't work
>>> to just use the lowest RTI involved in the join, though; the others
>>> won't appear anywhere else at that query level.
>
>
>> So +1 for
>> using the smallest RTI to indicate a subquery.
>
>
> +1 for the general idea.
>
> ISTM that the use of the same RTI for subqueries in multi-levels in a remote
> SQL makes the SQL a bit difficult to read. How about using the position of
> the join rel in join_rel_list, (more precisely, the position plus
> list_length(root->parse->rtable)), instead?
>
We switch to hash table to maintain the join RelOptInfos when the
number of joins grows larger, where the position won't make much
sense. We might differentiate between a base relation alias and
subquery alias by using different prefixes like "r" and "s" resp.

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