Re: SELECT Query taking 200 ms on PostgreSQL compared to 4 ms on Oracle after migration.

Noted thanks!!

On Sun, Apr 4, 2021 at 4:19 PM Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
wrote:

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>
> ne 4. 4. 2021 v 12:39 odesílatel aditya desai <admad123(at)gmail(dot)com> napsal:
>
>> Hi Pavel,
>> Notes thanks. We have 64 core cpu and 320 GB RAM.
>>
>
> ok - this is probably good for max thousand connections, maybe less (about
> 6 hundred). Postgres doesn't perform well, when there are too many active
> queries. Other databases have limits for active queries, and then use an
> internal queue. But Postgres has nothing similar.
>
>
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>
>
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>
>> Regards,
>> Aditya.
>>
>> On Sat, Apr 3, 2021 at 11:21 PM Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
>> wrote:
>>
>>>
>>>
>>> so 3. 4. 2021 v 19:45 odesílatel aditya desai <admad123(at)gmail(dot)com>
>>> napsal:
>>>
>>>> Yes. I have made suggestions on connection pooling as well. Currently
>>>> it is being done from Application side.
>>>>
>>>
>>> It is usual - but the application side pooling doesn't solve well
>>> overloading. The behaviour of the database is not linear. Usually opened
>>> connections are not active. But any non active connection can be changed to
>>> an active connection (there is not any limit for active connections), and
>>> then the performance can be very very slow. Good pooling and good setting
>>> of max_connections is protection against overloading. max_connection should
>>> be 10-20 x CPU cores (for OLTP)
>>>
>>> Regards
>>>
>>> Pavel
>>>
>>>
>>>
>>>
>>>> On Sat, Apr 3, 2021 at 11:12 PM Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
>>>> wrote:
>>>>
>>>>>
>>>>>
>>>>> so 3. 4. 2021 v 19:37 odesílatel aditya desai <admad123(at)gmail(dot)com>
>>>>> napsal:
>>>>>
>>>>>> Hi Justin/Bruce/Pavel,
>>>>>> Thanks for your inputs. After setting force_parallel_mode=off
>>>>>> Execution time of same query was reduced to 1ms from 200 ms. Worked like a
>>>>>> charm. We also increased work_mem to 80=MB. Thanks
>>>>>>
>>>>>
>>>>> super.
>>>>>
>>>>> The too big max_connection can cause a lot of problems. You should
>>>>> install and use pgbouncer or pgpool II.
>>>>>
>>>>>
>>>>> https://scalegrid.io/blog/postgresql-connection-pooling-part-4-pgbouncer-vs-pgpool/
>>>>>
>>>>> Regards
>>>>>
>>>>> Pavel
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>> again.
>>>>>>
>>>>>> Regards,
>>>>>> Aditya.
>>>>>>
>>>>>> On Sat, Apr 3, 2021 at 9:14 PM aditya desai <admad123(at)gmail(dot)com>
>>>>>> wrote:
>>>>>>
>>>>>>> Thanks Justin. Will review all parameters and get back to you.
>>>>>>>
>>>>>>> On Sat, Apr 3, 2021 at 9:11 PM Justin Pryzby <pryzby(at)telsasoft(dot)com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> On Sat, Apr 03, 2021 at 11:39:19AM -0400, Tom Lane wrote:
>>>>>>>> > Bruce Momjian <bruce(at)momjian(dot)us> writes:
>>>>>>>> > > On Sat, Apr 3, 2021 at 08:38:18PM +0530, aditya desai wrote:
>>>>>>>> > >> Yes, force_parallel_mode is on. Should we set it off?
>>>>>>>> >
>>>>>>>> > > Yes. I bet someone set it without reading our docs:
>>>>>>>> >
>>>>>>>> > >
>>>>>>>> https://www.postgresql.org/docs/13/runtime-config-query.html#RUNTIME-CONFIG-QUERY-OTHER
>>>>>>>> >
>>>>>>>> > > --> Allows the use of parallel queries for testing purposes
>>>>>>>> even in cases
>>>>>>>> > > --> where no performance benefit is expected.
>>>>>>>> >
>>>>>>>> > > We might need to clarify this sentence to be clearer it is
>>>>>>>> _only_ for
>>>>>>>> > > testing.
>>>>>>>> >
>>>>>>>> > I wonder why it is listed under planner options at all, and not
>>>>>>>> under
>>>>>>>> > developer options.
>>>>>>>>
>>>>>>>> Because it's there to help DBAs catch errors in functions
>>>>>>>> incorrectly marked as
>>>>>>>> parallel safe.
>>>>>>>>
>>>>>>>> --
>>>>>>>> Justin
>>>>>>>>
>>>>>>>