Subject: Re: [GENERAL] Queries are taking way longer in 9.6 than 9.5
To: Ravi Tammineni <rtammineni@partner.aligntech.com>,
 "pgsql-admin@postgresql.org" <pgsql-admin@postgresql.org>,
 "pgsql-general@postgresql.org" <pgsql-general@postgresql.org>,
 "pgadmin-support@postgresql.org" <pgadmin-support@postgresql.org>
References: 
 <MWHPR02MB2655591A4E27B425FABD5E93807C0@MWHPR02MB2655.namprd02.prod.outlook.com>
From: Adrian Klaver <adrian.klaver@aklaver.com>
Message-ID: <83d13711-6431-d944-ce42-6e73bc649bf2@aklaver.com>
Date: Tue, 17 Jan 2017 11:42:20 -0800
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On 01/17/2017 11:31 AM, Ravi Tammineni wrote:
> Hi,
>
>
>
> We have recently upgraded to 9.6 and few queries are performing very
> poorly. Query execution time has increased more 4 or 5 times in 9.6.
> Qeruy execution plan is also completely changed. I am not sure whether
> its because of Parallel feature or any bug in 9.6. There are few similar
> kind of queries and all of them are taking more time in 9.6.

How did you upgrade from 9.5 --> 9.6?

Did you run ANALYZE on the tables after the upgrade?

Tend to doubt parallel query is at issue here, as it is turned off by 
default:

https://www.postgresql.org/docs/9.6/static/runtime-config-resource.html#GUC-MAX-PARALLEL-WORKERS-PER-GATHER

For more info:

https://www.postgresql.org/docs/9.6/static/parallel-query.html
>
>
>
> Following query is taking 70ms in 9.5 and the same query is taking 2
> minutes in 9.6. Execution plan is totally different in 9.6 and seems
> like there is a major flaw while generating the execution plan. Instead
> of filtering the low cardinality, its filtering from biggest table.
> Somehow nested loop joins are screwed up.
>
>
>
>
>
> I really appreciate your help.
>
>
>
> explain analyze
>
> SELECT count(*)
>
> FROM
>
>     tblCnPatientOrderMap po
>
>     JOIN tblPuOrderStatus os ON po.vip_order_id = os.vip_order_id
>
>     JOIN tblPuOrderStatusHistory osh ON os.order_status_history_id =
> osh.order_status_history_id
>
> WHERE
>
>     exists(SELECT 1
>
>            FROM
>
>                tblCnDoctorPatientMap d
>
>            WHERE d.vip_patient_id = po.vip_patient_id
>
>                  AND exists(SELECT 1
>
>                             FROM
>
>                                 tblCnAccounts a
>
>                             WHERE a.master_user_id = d.master_user_id AND
>
>                                   a.user_name = 'dddddd'))
>
>     AND osh.vip_order_type IN (17)--assist
>
>     --AND osh.tx_submit_date IS NOT NULL
>
>     AND osh.cancelled_date IS NULL
>
>     AND osh.cc_accept_date IS NOT NULL;
>
>
>
>
>
> ##########################  9.5 Execution plan
>
>
>
>
> QUERY PLAN
>
> -----------------------------------------------------------------------------------------------------------------------------------------------------
>
> Aggregate  (cost=1177.25..1177.26 rows=1 width=0)
>
>    ->  Nested Loop  (cost=67.83..1177.25 rows=5 width=0)
>
>          ->  Nested Loop  (cost=67.71..254.81 rows=1322 width=4)
>
>                ->  Nested Loop  (cost=67.63..104.45 rows=1322 width=4)
>
>                      ->  HashAggregate  (cost=67.54..68.12 rows=192 width=4)
>
>                            Group Key: d.vip_patient_id
>
>
>
>                            ->  Nested Loop  (cost=0.17..67.44 rows=192
> width=4)
>
>                                  ->  Index Scan using unq_user_name on
> tblcnaccounts a  (cost=0.08..4.09 rows=1 width=4)
>
>                                        Index Cond: ((user_name)::text =
> 'dddddd'::text)
>
>
>
>                                  ->  Index Only Scan using
> idx_tblcndoctorpatientmap on tblcndoctorpatientmap d  (cost=0.09..62.78
> rows=192 width=8)
>
>                                        Index Cond: (master_user_id =
> a.master_user_id)
>
>                      ->  Index Scan using idx_tblcnpatientordermap on
> tblcnpatientordermap po  (cost=0.09..0.17 rows=7 width=8)
>
>                            Index Cond: (vip_patient_id = d.vip_patient_id)
>
>                ->  Index Scan using tblpuorderstatus_pkey on
> tblpuorderstatus os  (cost=0.09..0.11 rows=1 width=8)
>
>                      Index Cond: (vip_order_id = po.vip_order_id)
>
>          ->  Index Scan using tblpuorderstatushistory_pkey on
> tblpuorderstatushistory osh  (cost=0.11..0.69 rows=1 width=4)
>
>                Index Cond: (order_status_history_id =
> os.order_status_history_id)
>
>                Filter: ((cancelled_date IS NULL) AND (cc_accept_date IS
> NOT NULL) AND (vip_order_type = 17))
>
>
>
> #####################################################################################################################################
>
>
>
> ##########################  9.6 Execution plan
>
>                                                              QUERY PLAN
>
> -------------------------------------------------------------------------------------------------------------------------------------
>
> Aggregate  (cost=3185034.17..3185034.17 rows=1 width=8)
>
>    ->  Nested Loop Semi Join  (cost=3012833.92..3185010.91 rows=46511
> width=0)
>
>
>
>          ->  Nested Loop  (cost=3012833.75..3137291.51 rows=46511 width=4)
>
>
>
>                ->  Hash Join  (cost=3012833.67..3117860.77 rows=46511
> width=4)
>
>                      Hash Cond: (os.order_status_history_id =
> osh.order_status_history_id)
>
>
>
>                      ->  Seq Scan on tblpuorderstatus os
> (cost=0.00..96498.46 rows=11185486 width=8)
>
>                      ->  Hash  (cost=3010979.77..3010979.77 rows=529686
> width=4)
>
>                            ->  Gather  (cost=1000.00..3010979.77
> rows=529686 width=4)
>
>                                  Workers Planned: 2
>
>                                  ->  Parallel Seq Scan on
> tblpuorderstatushistory osh  (cost=0.00..2957011.17 rows=220702 width=4)
>
>
>
>                                        Filter: ((cancelled_date IS NULL)
> AND (cc_accept_date IS NOT NULL) AND (vip_order_type = 17))
>
>
>
>                ->  Index Scan using tblcnpatientordermap_pkey on
> tblcnpatientordermap po  (cost=0.09..0.41 rows=1 width=8)
>
>
>
>                      Index Cond: (vip_order_id = os.vip_order_id)
>
>
>
>          ->  Nested Loop Semi Join  (cost=0.17..1.02 rows=1 width=4)
>
>                ->  Index Scan using tblcndoctorpatientmap_pkey on
> tblcndoctorpatientmap d  (cost=0.09..0.39 rows=1 width=8)
>
>                      Index Cond: (vip_patient_id = po.vip_patient_id)
>
>                ->  Index Scan using tblcnaccounts_pkey on tblcnaccounts
> a  (cost=0.08..0.36 rows=1 width=4)
>
>                      Index Cond: (master_user_id = d.master_user_id)
>
>                      Filter: ((user_name)::text = 'dddddd'::text)
>
> (19 rows)
>
>
>
>
>
> Regards,
>
> ravi
>


-- 
Adrian Klaver
adrian.klaver@aklaver.com


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