Re: An issue in remote query optimization

On Tue, Jan 31, 2017 at 5:23 PM, Abbas Butt <abbas(dot)butt(at)enterprisedb(dot)com> wrote:
>
>
> On Tue, Jan 31, 2017 at 3:15 AM, Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>
> wrote:
>>
>> On 2017/01/31 19:53, Abbas Butt wrote:
>>>
>>> On Tue, Jan 31, 2017 at 2:25 AM, Etsuro Fujita
>>> <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp <mailto:fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>> wrote:
>>> On 2017/01/31 18:24, Abbas Butt wrote:
>>
>>
>>> Postgres_fdw optimizes remote queries by pushing down the where
>>> clause.
>>> This feature does not work consistently when the query is
>>> executed from
>>> within a pl/pgsql function. The optimization works when the
>>> function
>>> executes the query for the first 5 times, and fails afterwards.
>>
>>
>>> I understand that this is because PostgreSQL starts using
>>> generic plan
>>> with pulled up where clause after the 5th invocation hoping that
>>> it
>>> would be faster since we have skiped planning the query on each
>>> invocation, but in this case this decision is causing the query
>>> to slow
>>> down.
>>
>>
>>> How should we fix this problem?
>>
>>
>>> ANALYZE for the foreign table doesn't work?
>>
>>
>>> No.
>>>
>>> analyze ts.tickets;
>>> WARNING: skipping "tickets" --- cannot analyze this foreign table
>>> ANALYZE
>>
>>
>> How the foreign table ts.tickets is defined?
>
>
> test=# \d ts.tickets
> Foreign table "ts.tickets"
> Column | Type | Modifiers | FDW Options
> --------+---------+-----------+-------------
> id | integer | not null |
> Server: mysql_server
> FDW Options: (dbname 'msql_test_db', table_name 'tickets')
>
> Its a foreign table, referring to table 'tickets' defined on MySQL.
>
Isn't your original complaint about postgres_fdw? You can not tickets,
which is a mongo_fdw foreign table, is probably because mongo_fdw has
not implemented analyze FDW routine.

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