Query Transformation

From: Patrick Jolliffe <jolliffe_at_gmail.com>
Date: Mon, 25 Jan 2021 09:40:15 +0000
Message-ID: <CABx0cSXqyu+4a114Pi-+NkKT+tNWGtkmH0R3DgWdGKP5UNVB2A_at_mail.gmail.com>

Dear List,
On Oracle 19c been looking at a poorly performing plan for a little while now. I've simplified it somewhat as per the details below. I've resolved the problem itself by
1) creating an extended statistic for column group GMOBJ, GMSUB (which were correlated)
2) getting developers to replace the 2 binds :nc1 and :nc2 with a single bind, as the values are actually the same although the optimizer doesn't know this, so this limits it's options.
However I've got myself bogged down in trying to understand the transformation that has taken place, really for intellectual curiosity. I think it's some variation on "cost based or expansion", but how has it transformed into a union of 3 different parts? Any help greatly appreciated
Patrick

SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR(FORMAT=>'ALLSTATS LAST')); PLAN_TABLE_OUTPUT

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SQL_ID 5f67d104uv8ht, child number 0

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SELECT /*+gather_plan_statistics Y */ null FROM P, C1, C2 WHERE ( ( C1.RZVR01 = :nc1 AND C2.GMOBJ BETWEEN '2201' AND '2299') OR ( C1.RZVR01 = :nc2 AND C2.GMOBJ = '2019' AND C2.GMSUB = 'IDT' ) ) AND

    ( P.RYPYID = C1.RZPYID AND P.RYGLBA = C2.GMAID ) Plan hash value: 1470685083

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| Id | Operation | Name | Starts | E-Rows | A-Rows
| A-Time | Buffers |

---

| 0 | SELECT STATEMENT | | 1 | | 0
|00:00:00.18 | 89916 |
| 1 | CONCATENATION | | 1 | | 0
|00:00:00.18 | 89916 |
| 2 | NESTED LOOPS | | 1 | 1 | 0
|00:00:00.18 | 89886 |
| 3 | NESTED LOOPS | | 1 | 1 | 89115
|00:00:00.13 | 771 |
| 4 | NESTED LOOPS | | 1 | 1 | 89115
|00:00:00.06 | 745 |
| 5 | INLIST ITERATOR | | 1 | | 3
|00:00:00.01 | 8 |
|* 6 | INDEX RANGE SCAN | C1_I | 2 | 3 | 3
|00:00:00.01 | 8 |
|* 7 | INDEX RANGE SCAN | C21I | 3 | 1 | 89115
|00:00:00.05 | 737 |
|* 8 | INDEX UNIQUE SCAN | P_PK | 89115 | 1 | 89115
|00:00:00.04 | 26 |
|* 9 | TABLE ACCESS BY INDEX ROWID | P | 89115 | 1 | 0
|00:00:00.05 | 89115 |
| 10 | NESTED LOOPS | | 1 | 1 | 0
|00:00:00.01 | 26 |
| 11 | NESTED LOOPS | | 1 | 1 | 3
|00:00:00.01 | 15 |
|* 12 | INDEX RANGE SCAN | C1_I | 1 | 1 | 3
|00:00:00.01 | 4 |
| 13 | TABLE ACCESS BY INDEX ROWID | P | 3 | 1 | 3
|00:00:00.01 | 11 |
|* 14 | INDEX UNIQUE SCAN | P_PK | 3 | 1 | 3
|00:00:00.01 | 8 |
|* 15 | INDEX RANGE SCAN | C21I | 3 | 1 | 0
|00:00:00.01 | 11 |
| 16 | NESTED LOOPS | | 1 | 1 | 0
|00:00:00.01 | 4 |
| 17 | NESTED LOOPS | | 1 | 1 | 0
|00:00:00.01 | 4 |
| 18 | NESTED LOOPS | | 1 | 1 | 0
|00:00:00.01 | 4 |
|* 19 | INDEX RANGE SCAN | C1_I | 1 | 1 | 0
|00:00:00.01 | 4 |
| 20 | TABLE ACCESS BY INDEX ROWID| P | 0 | 1 | 0
|00:00:00.01 | 0 |
|* 21 | INDEX UNIQUE SCAN | P_PK | 0 | 1 | 0
|00:00:00.01 | 0 |
|* 22 | INDEX UNIQUE SCAN | C2_PK | 0 | 1 | 0
|00:00:00.01 | 0 |
|* 23 | TABLE ACCESS BY INDEX ROWID | C2 | 0 | 1 | 0
|00:00:00.01 | 0 |

---

Predicate Information (identified by operation id):

---

   6 - access(("C1"."RZVR01"=:NC1 OR "C1"."RZVR01"=:NC2))
   7 - access("C2"."GMOBJ"=U'2019' AND "C2"."GMSUB"=U'IDT')
       filter((("C1"."RZVR01"=:NC1 AND "C2"."GMOBJ">=U'2201' AND
"C2"."GMOBJ"<=U'2299') OR
              ("C1"."RZVR01"=:NC2 AND "C2"."GMOBJ"=U'2019' AND

"C2"."GMSUB"=U'IDT')))

   8 - access("P"."RYPYID"="C1"."RZPYID")
   9 - filter("P"."RYGLBA"="C2"."GMAID")
  12 - access("C1"."RZVR01"=:NC2)
       filter(("C1"."RZVR01"=:NC1 OR "C1"."RZVR01"=:NC2))

  14 - access("P"."RYPYID"="C1"."RZPYID")   15 - access("C2"."GMOBJ"=U'2019' AND "C2"."GMSUB"=U'IDT' AND "P"."RYGLBA"="C2"."GMAID")

       filter(("C2"."GMOBJ"<=U'2299' AND "C2"."GMOBJ">=U'2201' AND
              (LNNVL("C2"."GMSUB"=U'IDT') OR LNNVL("C2"."GMOBJ"=U'2019'))))
  19 - access("C1"."RZVR01"=:NC1)
       filter(("C1"."RZVR01"=:NC1 OR "C1"."RZVR01"=:NC2))
  21 - access("P"."RYPYID"="C1"."RZPYID")

  22 - access("P"."RYGLBA"="C2"."GMAID")   23 - filter(("C2"."GMOBJ"<=U'2299' AND "C2"."GMOBJ"<=U'2299' AND "C2"."GMOBJ">=U'2201'
              AND "C2"."GMOBJ">=U'2201' AND (LNNVL("C1"."RZVR01"=:NC2) OR LNNVL("C2"."GMOBJ"=U'2019') OR

              LNNVL("C2"."GMSUB"=U'IDT')) AND (LNNVL("C2"."GMSUB"=U'IDT') OR
              LNNVL("C2"."GMOBJ"=U'2019'))))

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Received on Mon Jan 25 2021 - 10:40:15 CET