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Re: Slow performance

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Hi Again,

I have not gone through your explain plans for both, will it be possible for you to take diff of the both plans. It will give some insight about how things are going and where the problem is.

Alternatively

I will suggest Reindex and  execute ANALYZE command to regenerate stats .

Regards,
Ikram


On Fri, Jul 26, 2024 at 11:05 AM sivapostgres@xxxxxxxxx <sivapostgres@xxxxxxxxx> wrote:
I've only one instance of PG in that server.  Means only one postgresql.conf for both databases.


On Friday, 26 July, 2024 at 11:12:34 am IST, Muhammad Ikram <mmikram@xxxxxxxxx> wrote:


Hi,

Could you perform diff on postgresql.conf file to see whether values are same for work_mem, shared_buffers, maintenance_work_mem and other related parameters?

Regards,
Ikram


On Fri, Jul 26, 2024 at 10:31 AM sivapostgres@xxxxxxxxx <sivapostgres@xxxxxxxxx> wrote:
Hello,
Using PG 11.11, One PG Cluster, Windows 2019 Server Standard, Two databases with identical data.

1.  First DB:  client_db
2.  Second DB: client_test

Took backup (pg_dump) of first database (client_db) and restored the database as second database (client_test).

Query:
 Select a.examname, a.registrationnumber, b.studentname, d.departmentname, e.levelname, 
        a.subjectcode, c.subjectname, b.regular, a.semester, a.dummynumber, p.semester as curr_sem, 
        a.internalmark, a.externalmark, a.result, coalesce((a.internalmark + a.externalmark),0) as total, 
        a.absent, a.malpractice, c.maxinternalmark, f.noofsemester, a.examstudentstatus, 
        Case When a.result = 'P'  Then 'P' Else 
        Case When a.result = 'F' and a.malpractice = 'Y' and a.examstudentstatus is null Then 'M' Else 
        Case When a.result = 'F' and a.absent = 'Y' and a.examstudentstatus = 'R' Then 'R.C' Else 
        Case When a.result = 'F' and a.absent = 'Y' and a.examstudentstatus = 'S' Then 'S.L' Else 
        Case When a.result = 'F' and a.absent = 'Y' and a.examstudentstatus = 'F' Then 'N.P' Else 
        Case When a.result = 'F' and a.absent = 'Y' and a.examstudentstatus = 'W' Then 'W.H' Else 
                                                    'RA' End End End End End End as res, 
        Concat(RTrim(f.degreeawarded), ' ', RTrim(d.departmentname))  as course, 
        a.revaluation, m.absent as int_abs, n.companyname, n.companydescription, 
        m.totalmark as int_mark, q.addressone, q.addresstwo, 
        Case When a.semester > f.noofsemester Then 'PRIVATE' 
             When a.semester <= f.noofsemester and a.semester in (1,2) Then 'I - Year' 
             When a.semester <= f.noofsemester and a.semester in (3,4) Then 'II - Year' 
             When a.semester <= f.noofsemester and a.semester in (5,6) Then 'III - Year' End as studyr, 
       c.subjectserialno, p.regulararrear 
 From  cl_student_exam_subject  a 
 Join  cl_student_name b 
 On    b.companycode = a.companycode 
 And   b.registrationnumber = a.registrationnumber 
 Join  cl_subject c 
 On    c.companycode = a.companycode 
 And   c.subjectcode    = a.subjectcode 
 Join  cl_department_header d 
 On   d.departmentheaderpk = b.departmentheaderfk 
 Join  cl_level e 
 On   e.levelpk = b.Levelfk 
 Join  cl_department_detail f 
 On   f.departmentheaderfk = b.departmentheaderfk 
 And   f.levelfk = b.levelfk 
 Left Outer Join cl_student_internal_mark m 
 On    m.companycode = a.companycode 
 And   m.registrationnumber = a.registrationnumber 
 And   m.subjectcode = a.subjectcode 
 And   m.departmentheaderfk = b.departmentheaderfk 
 And   m.levelfk = b.levelfk 
 And   m.Regular = b.Regular 
 Join  co_company n 
 On    n.companycode = a.companycode 
 Join  cl_student_semester_subject p 
 On    p.companycode = a.companycode 
 And   p.examheaderfk = a.examheaderfk 
 And   p.subjectcode  = a.subjectcode 
 And   p.registrationnumber = a.registrationnumber 
 And   p.semester = a.semester 
 Join  co_company_branch q 
 On    n.companycode = a.companycode 
 Where  a.companycode = '100'
 And    a.examheaderfk = 'BA80952CFF8F4E1C3F9F44B62ED9BF37'
 And   (a.examstudentstatus is null or a.examstudentstatus in ('R', 'S', 'W')) 
 And  b.departmentheaderfk in ('04DF8BD89D0844DD4D8AA151EFB28657')
 And    b.levelfk in ('37A9BEC2638844FFD5B1422D83E70EF3')
 And    b.status = 'A' 
 Order By Concat(RTrim(f.degreeawarded), ' ', RTrim(d.departmentname)), 
          Case When a.semester > f.noofsemester Then 'PRIVATE' 
               When a.semester <= f.noofsemester and a.semester in (1,2) Then 'I - Year' 
               When a.semester <= f.noofsemester and a.semester in (3,4) Then 'II - Year' 
               When a.semester <= f.noofsemester and a.semester in (5,6) Then 'III - Year' End, 
          a.registrationnumber, b.regular, p.semester desc, c.subjectserialno, 
  Case When c.subjectcategory = 'T' Then 1 
    When c.subjectcategory = 'P' Then 2 
    When c.subjectcategory = 'D' Then 3 
    When c.subjectcategory = 'V' Then 4 
    When c.subjectcategory = 'J' Then 5 End, 
  c.ancillary, 
  Case When Substring(a.subjectcode, 6, 1) = 'C' Then 1 
       When Substring(a.subjectcode, 6, 1) = 'S' Then 2 
       When Substring(a.subjectcode, 6, 1) = 'A' Then 3 
       When Substring(a.subjectcode, 6, 1) = 'E' Then 4 Else 5 End, 
     a.subjectcode 


Explain Analyze of DB 1 (client_db) :
"Sort  (cost=2862.35..2862.36 rows=1 width=1088) (actual time=451671.464..451671.495 rows=326 loops=1)"
"  Sort Key: (concat(rtrim((f.degreeawarded)::text), ' ', rtrim((d.departmentname)::text))), (CASE WHEN (a.semester > f.noofsemester) THEN 'PRIVATE'::text WHEN ((a.semester <= f.noofsemester) AND (a.semester = ANY ('{1,2}'::integer[]))) THEN 'I - Year'::text WHEN ((a.semester <= f.noofsemester) AND (a.semester = ANY ('{3,4}'::integer[]))) THEN 'II - Year'::text WHEN ((a.semester <= f.noofsemester) AND (a.semester = ANY ('{5,6}'::integer[]))) THEN 'III - Year'::text ELSE NULL::text END), a.registrationnumber, b.regular, a.semester DESC, c.subjectserialno, (CASE WHEN (c.subjectcategory = 'T'::bpchar) THEN 1 WHEN (c.subjectcategory = 'P'::bpchar) THEN 2 WHEN (c.subjectcategory = 'D'::bpchar) THEN 3 WHEN (c.subjectcategory = 'V'::bpchar) THEN 4 WHEN (c.subjectcategory = 'J'::bpchar) THEN 5 ELSE NULL::integer END), c.ancillary, (CASE WHEN (""substring""((a.subjectcode)::text, 6, 1) = 'C'::text) THEN 1 WHEN (""substring""((a.subjectcode)::text, 6, 1) = 'S'::text) THEN 2 WHEN (""substring""((a.subjectcode)::text, 6, 1) = 'A'::text) THEN 3 WHEN (""substring""((a.subjectcode)::text, 6, 1) = 'E'::text) THEN 4 ELSE 5 END), a.subjectcode"
"  Sort Method: quicksort  Memory: 193kB"
"  ->  Nested Loop  (cost=2.36..2862.34 rows=1 width=1088) (actual time=57829.857..451662.727 rows=326 loops=1)"
"        ->  Nested Loop  (cost=2.36..2861.23 rows=1 width=686) (actual time=57829.829..451658.085 rows=326 loops=1)"
"              Join Filter: (((b.registrationnumber)::text = (p.registrationnumber)::text) AND ((c.subjectcode)::text = (p.subjectcode)::text) AND (a.semester = p.semester))"
"              Rows Removed by Join Filter: 13614738"
"              ->  Index Scan using ""cl_student_semester_subject_IX3"" on cl_student_semester_subject p  (cost=0.55..8.57 rows=1 width=60) (actual time=0.033..55.702 rows=41764 loops=1)"
"                    Index Cond: (((companycode)::text = '100'::text) AND ((examheaderfk)::text = 'BA80952CFF8F4E1C3F9F44B62ED9BF37'::text))"
"              ->  Nested Loop Left Join  (cost=1.81..2848.39 rows=244 width=735) (actual time=0.068..10.768 rows=326 loops=41764)"
"                    Join Filter: (((m.departmentheaderfk)::text = (b.departmentheaderfk)::text) AND ((m.levelfk)::text = (b.levelfk)::text) AND (m.regular = b.regular))"
"                    ->  Nested Loop  (cost=1.39..2135.32 rows=244 width=795) (actual time=0.053..6.723 rows=326 loops=41764)"
"                          ->  Nested Loop  (cost=1.11..2058.12 rows=244 width=746) (actual time=0.045..4.299 rows=326 loops=41764)"
"                                ->  Nested Loop  (cost=0.68..312.80 rows=172 width=699) (actual time=0.029..0.338 rows=313 loops=41764)"
"                                      ->  Seq Scan on co_company n  (cost=0.00..1.01 rows=1 width=394) (actual time=0.001..0.001 rows=1 loops=41764)"
"                                            Filter: ((companycode)::text = '100'::text)"
"                                      ->  Nested Loop  (cost=0.68..310.07 rows=172 width=305) (actual time=0.025..0.282 rows=313 loops=41764)"
"                                            ->  Nested Loop  (cost=0.27..10.70 rows=1 width=438) (actual time=0.013..0.019 rows=1 loops=41764)"
"                                                  ->  Nested Loop  (cost=0.27..9.60 rows=1 width=278) (actual time=0.009..0.013 rows=1 loops=41764)"
"                                                        ->  Seq Scan on cl_department_header d  (cost=0.00..1.30 rows=1 width=200) (actual time=0.002..0.004 rows=1 loops=41764)"
"                                                              Filter: ((departmentheaderpk)::text = '04DF8BD89D0844DD4D8AA151EFB28657'::text)"
"                                                              Rows Removed by Filter: 23"
"                                                        ->  Index Scan using cl_department_detail_ix1 on cl_department_detail f  (cost=0.27..8.29 rows=1 width=78) (actual time=0.007..0.007 rows=1 loops=41764)"
"                                                              Index Cond: (((departmentheaderfk)::text = '04DF8BD89D0844DD4D8AA151EFB28657'::text) AND ((levelfk)::text = '37A9BEC2638844FFD5B1422D83E70EF3'::text))"
"                                                  ->  Seq Scan on cl_level e  (cost=0.00..1.09 rows=1 width=160) (actual time=0.001..0.003 rows=1 loops=41764)"
"                                                        Filter: ((levelpk)::text = '37A9BEC2638844FFD5B1422D83E70EF3'::text)"
"                                                        Rows Removed by Filter: 6"
"                                            ->  Index Scan using cl_student_name_ix4 on cl_student_name b  (cost=0.41..297.65 rows=172 width=97) (actual time=0.011..0.165 rows=313 loops=41764)"
"                                                  Index Cond: (((companycode)::text = '100'::text) AND ((departmentheaderfk)::text = '04DF8BD89D0844DD4D8AA151EFB28657'::text) AND ((levelfk)::text = '37A9BEC2638844FFD5B1422D83E70EF3'::text) AND (status = 'A'::bpchar))"
"                                ->  Index Scan using ""cl_student_exam_subject_IX1"" on cl_student_exam_subject a  (cost=0.42..10.13 rows=2 width=89) (actual time=0.012..0.012 rows=1 loops=13072132)"
"                                      Index Cond: (((companycode)::text = '100'::text) AND ((examheaderfk)::text = 'BA80952CFF8F4E1C3F9F44B62ED9BF37'::text) AND ((registrationnumber)::text = (b.registrationnumber)::text))"
"                                      Filter: ((examstudentstatus IS NULL) OR (examstudentstatus = ANY ('{R,S,W}'::bpchar[])))"
"                          ->  Index Scan using cl_subject_ix3 on cl_subject c  (cost=0.28..0.32 rows=1 width=53) (actual time=0.007..0.007 rows=1 loops=13615064)"
"                                Index Cond: (((companycode)::text = '100'::text) AND ((subjectcode)::text = (a.subjectcode)::text))"
"                    ->  Index Scan using ""cl_student_internal_mark_IX"" on cl_student_internal_mark m  (cost=0.42..2.90 rows=1 width=97) (actual time=0.011..0.011 rows=1 loops=13615064)"
"                          Index Cond: (((companycode)::text = (a.companycode)::text) AND ((companycode)::text = '100'::text) AND ((subjectcode)::text = (a.subjectcode)::text) AND ((registrationnumber)::text = (a.registrationnumber)::text))"
"                          Filter: (((departmentheaderfk)::text = '04DF8BD89D0844DD4D8AA151EFB28657'::text) AND ((levelfk)::text = '37A9BEC2638844FFD5B1422D83E70EF3'::text))"
"        ->  Seq Scan on co_company_branch q  (cost=0.00..1.01 rows=1 width=276) (actual time=0.001..0.001 rows=1 loops=326)"
"Planning Time: 15.936 ms"
"Execution Time: 451672.059 ms"



Explain Analyze of Second DB (client_test)
"Sort  (cost=3454.91..3454.92 rows=1 width=1088) (actual time=19.120..19.137 rows=326 loops=1)"
"  Sort Key: (concat(rtrim((f.degreeawarded)::text), ' ', rtrim((d.departmentname)::text))), (CASE WHEN (a.semester > f.noofsemester) THEN 'PRIVATE'::text WHEN ((a.semester <= f.noofsemester) AND (a.semester = ANY ('{1,2}'::integer[]))) THEN 'I - Year'::text WHEN ((a.semester <= f.noofsemester) AND (a.semester = ANY ('{3,4}'::integer[]))) THEN 'II - Year'::text WHEN ((a.semester <= f.noofsemester) AND (a.semester = ANY ('{5,6}'::integer[]))) THEN 'III - Year'::text ELSE NULL::text END), a.registrationnumber, b.regular, a.semester DESC, c.subjectserialno, (CASE WHEN (c.subjectcategory = 'T'::bpchar) THEN 1 WHEN (c.subjectcategory = 'P'::bpchar) THEN 2 WHEN (c.subjectcategory = 'D'::bpchar) THEN 3 WHEN (c.subjectcategory = 'V'::bpchar) THEN 4 WHEN (c.subjectcategory = 'J'::bpchar) THEN 5 ELSE NULL::integer END), c.ancillary, (CASE WHEN (""substring""((a.subjectcode)::text, 6, 1) = 'C'::text) THEN 1 WHEN (""substring""((a.subjectcode)::text, 6, 1) = 'S'::text) THEN 2 WHEN (""substring""((a.subjectcode)::text, 6, 1) = 'A'::text) THEN 3 WHEN (""substring""((a.subjectcode)::text, 6, 1) = 'E'::text) THEN 4 ELSE 5 END), a.subjectcode"
"  Sort Method: quicksort  Memory: 193kB"
"  ->  Nested Loop  (cost=2.23..3454.90 rows=1 width=1088) (actual time=0.319..14.984 rows=326 loops=1)"
"        ->  Nested Loop  (cost=2.23..3453.78 rows=1 width=686) (actual time=0.298..13.691 rows=326 loops=1)"
"              Join Filter: (((b.registrationnumber)::text = (p.registrationnumber)::text) AND ((c.subjectcode)::text = (p.subjectcode)::text))"
"              ->  Nested Loop Left Join  (cost=1.81..2739.81 rows=230 width=735) (actual time=0.259..9.970 rows=326 loops=1)"
"                    Join Filter: (((m.departmentheaderfk)::text = (b.departmentheaderfk)::text) AND ((m.levelfk)::text = (b.levelfk)::text) AND (m.regular = b.regular))"
"                    ->  Nested Loop  (cost=1.39..2060.47 rows=230 width=795) (actual time=0.233..6.232 rows=326 loops=1)"
"                          ->  Nested Loop  (cost=1.11..1987.62 rows=230 width=746) (actual time=0.211..3.955 rows=326 loops=1)"
"                                ->  Nested Loop  (cost=0.68..299.78 rows=166 width=699) (actual time=0.118..0.393 rows=313 loops=1)"
"                                      ->  Seq Scan on co_company n  (cost=0.00..1.01 rows=1 width=394) (actual time=0.026..0.027 rows=1 loops=1)"
"                                            Filter: ((companycode)::text = '100'::text)"
"                                      ->  Nested Loop  (cost=0.68..297.11 rows=166 width=305) (actual time=0.091..0.316 rows=313 loops=1)"
"                                            ->  Nested Loop  (cost=0.27..10.70 rows=1 width=438) (actual time=0.041..0.048 rows=1 loops=1)"
"                                                  ->  Nested Loop  (cost=0.27..9.60 rows=1 width=278) (actual time=0.034..0.038 rows=1 loops=1)"
"                                                        ->  Seq Scan on cl_department_header d  (cost=0.00..1.30 rows=1 width=200) (actual time=0.009..0.011 rows=1 loops=1)"
"                                                              Filter: ((departmentheaderpk)::text = '04DF8BD89D0844DD4D8AA151EFB28657'::text)"
"                                                              Rows Removed by Filter: 23"
"                                                        ->  Index Scan using cl_department_detail_ix1 on cl_department_detail f  (cost=0.27..8.29 rows=1 width=78) (actual time=0.024..0.024 rows=1 loops=1)"
"                                                              Index Cond: (((departmentheaderfk)::text = '04DF8BD89D0844DD4D8AA151EFB28657'::text) AND ((levelfk)::text = '37A9BEC2638844FFD5B1422D83E70EF3'::text))"
"                                                  ->  Seq Scan on cl_level e  (cost=0.00..1.09 rows=1 width=160) (actual time=0.006..0.008 rows=1 loops=1)"
"                                                        Filter: ((levelpk)::text = '37A9BEC2638844FFD5B1422D83E70EF3'::text)"
"                                                        Rows Removed by Filter: 6"
"                                            ->  Index Scan using cl_student_name_ix4 on cl_student_name b  (cost=0.41..284.75 rows=166 width=97) (actual time=0.049..0.184 rows=313 loops=1)"
"                                                  Index Cond: (((companycode)::text = '100'::text) AND ((departmentheaderfk)::text = '04DF8BD89D0844DD4D8AA151EFB28657'::text) AND ((levelfk)::text = '37A9BEC2638844FFD5B1422D83E70EF3'::text) AND (status = 'A'::bpchar))"
"                                ->  Index Scan using ""cl_student_exam_subject_IX1"" on cl_student_exam_subject a  (cost=0.42..10.15 rows=2 width=89) (actual time=0.010..0.011 rows=1 loops=313)"
"                                      Index Cond: (((companycode)::text = '100'::text) AND ((examheaderfk)::text = 'BA80952CFF8F4E1C3F9F44B62ED9BF37'::text) AND ((registrationnumber)::text = (b.registrationnumber)::text))"
"                                      Filter: ((examstudentstatus IS NULL) OR (examstudentstatus = ANY ('{R,S,W}'::bpchar[])))"
"                          ->  Index Scan using cl_subject_ix3 on cl_subject c  (cost=0.28..0.32 rows=1 width=53) (actual time=0.006..0.006 rows=1 loops=326)"
"                                Index Cond: (((companycode)::text = '100'::text) AND ((subjectcode)::text = (a.subjectcode)::text))"
"                    ->  Index Scan using ""cl_student_internal_mark_IX"" on cl_student_internal_mark m  (cost=0.42..2.94 rows=1 width=97) (actual time=0.010..0.010 rows=1 loops=326)"
"                          Index Cond: (((companycode)::text = (a.companycode)::text) AND ((companycode)::text = '100'::text) AND ((subjectcode)::text = (a.subjectcode)::text) AND ((registrationnumber)::text = (a.registrationnumber)::text))"
"                          Filter: (((departmentheaderfk)::text = '04DF8BD89D0844DD4D8AA151EFB28657'::text) AND ((levelfk)::text = '37A9BEC2638844FFD5B1422D83E70EF3'::text))"
"              ->  Index Scan using ""cl_student_semester_subject_IX1"" on cl_student_semester_subject p  (cost=0.42..3.09 rows=1 width=60) (actual time=0.010..0.010 rows=1 loops=326)"
"                    Index Cond: (((companycode)::text = '100'::text) AND ((subjectcode)::text = (a.subjectcode)::text) AND ((registrationnumber)::text = (a.registrationnumber)::text) AND (semester = a.semester))"
"                    Filter: ((examheaderfk)::text = 'BA80952CFF8F4E1C3F9F44B62ED9BF37'::text)"
"        ->  Seq Scan on co_company_branch q  (cost=0.00..1.01 rows=1 width=276) (actual time=0.000..0.000 rows=1 loops=326)"
"Planning Time: 15.581 ms"
"Execution Time: 19.546 ms"


The query when run against DB1 takes around 7 min 32 seconds.
The same query when run against DB2 takes around 124 msec.  

Same computer, same PG cluster, same query.
Why it takes so much time when run against DB1 (client_db)?

Already executed vacuum against client_db database.  

Any help is really appreciated.

Happiness Always
BKR Sivaprakash



--
Muhammad Ikram



--
Muhammad Ikram

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