How to debug an Oracle query given an explain plan? - sql

Question

IMAGE OF TOAD: query waits
WITH
NJ AS (SELECT CNATJUR FROM RE_CD.CDTD005_NATUR_JURIDICA WHERE DESCRICAO = 'Particulares' AND DTEND_VER = '9999-12-31 00:00' ),
PAISES AS (SELECT PAIS_BST FROM RE_CD.CDTD006_PAISES WHERE GRUPO_PAIS = 'RESTO UNIAO EUROPEIA' AND DTEND_VER = '9999-12-31 00:00' ),
GAR AS (SELECT /*+PARALLEL(4)*/ CCONTA, CREFERENCIA_IMP FROM RE_DM.DMTD002_GAR_CONTRATO WHERE TIPO_GAR = 'GAR REAL' AND TIPO_GAR2 = 'GAR DINERARIA' AND FLAG_PRIORIDADE = 1 AND IDVERSAO = (SELECT MAX(IDVERSAO) FROM RE_DM.DMTD001_VERSOES WHERE TABELA = 'RE_DM.DMTD002_GAR_CONTRATO' AND DTEND_VER = '9999-12-31 00:00' ) )
SELECT /*+PARALLEL(4)*/ MOROS.COD_PERIMETRO, MOROS.SOCIEDADE
FROM RE_DM.DMTF020_MOROS MOROS
INNER JOIN GAR ON MOROS.CCONTA = GAR.CCONTA AND MOROS.CREFERENCIA = GAR.CREFERENCIA_IMP
INNER JOIN NJ ON MOROS.COD_NATJUR = NJ.CNATJUR
INNER JOIN PAISES ON MOROS.COD_PAIS = PAISES.PAIS_BST
WHERE MOROS.IDVERSAO = 167
AND MOROS.SEGMENTO <> 'PC' AND MOROS.SEGMENTO <> 'LO' AND MOROS.SEGMENTO <> 'GA'
AND MOROS.SEGMENTO <> 'G1' AND MOROS.SEGMENTO <> 'G2' AND MOROS.SEGMENTO <> 'G3'
AND MOROS.INPUT = 'IMP'
AND MOROS.FLAG_MOROSIDADE = 0;
Plan hash value: 441958758
----------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | TQ |IN-OUT| PQ Distrib |
----------------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 76752 | 16M| 22115 (1)| 00:01:07 | | | |
| 1 | PX COORDINATOR | | | | | | | | |
| 2 | PX SEND QC (RANDOM) | :TQ20002 | 76752 | 16M| 22113 (1)| 00:01:07 | Q2,02 | P->S | QC (RAND) |
|* 3 | HASH JOIN | | 76752 | 16M| 22113 (1)| 00:01:07 | Q2,02 | PCWP | |
| 4 | PX RECEIVE | | 42 | 1512 | 2 (0)| 00:00:01 | Q2,02 | PCWP | |
| 5 | PX SEND BROADCAST | :TQ20000 | 42 | 1512 | 2 (0)| 00:00:01 | Q2,00 | P->P | BROADCAST |
| 6 | PX BLOCK ITERATOR | | 42 | 1512 | 2 (0)| 00:00:01 | Q2,00 | PCWC | |
|* 7 | TABLE ACCESS FULL | CDTD006_PAISES | 42 | 1512 | 2 (0)| 00:00:01 | Q2,00 | PCWP | |
|* 8 | HASH JOIN | | 237K| 41M| 22110 (1)| 00:01:07 | Q2,02 | PCWP | |
| 9 | PX RECEIVE | | 23 | 1150 | 2 (0)| 00:00:01 | Q2,02 | PCWP | |
| 10 | PX SEND BROADCAST | :TQ20001 | 23 | 1150 | 2 (0)| 00:00:01 | Q2,01 | P->P | BROADCAST |
| 11 | PX BLOCK ITERATOR | | 23 | 1150 | 2 (0)| 00:00:01 | Q2,01 | PCWC | |
|* 12 | TABLE ACCESS FULL | CDTD005_NATUR_JURIDICA | 23 | 1150 | 2 (0)| 00:00:01 | Q2,01 | PCWP | |
| 13 | NESTED LOOPS | | | | | | Q2,02 | PCWP | |
| 14 | NESTED LOOPS | | 795K| 100M| 22105 (1)| 00:01:07 | Q2,02 | PCWP | |
| 15 | PX BLOCK ITERATOR | | | | | | Q2,02 | PCWC | |
|* 16 | TABLE ACCESS FULL | DMTD002_GAR_CONTRATO | 6357 | 341K| 4423 (1)| 00:00:14 | Q2,02 | PCWP | |
| 17 | SORT AGGREGATE | | 1 | 42 | | | Q2,02 | PCWP | |
| 18 | PX COORDINATOR | | | | | | | | |
| 19 | PX SEND QC (RANDOM) | :TQ10000 | 1 | 42 | | | Q1,00 | P->S | QC (RAND) |
| 20 | SORT AGGREGATE | | 1 | 42 | | | Q1,00 | PCWP | |
| 21 | PX BLOCK ITERATOR | | 1 | 42 | 2 (0)| 00:00:01 | Q1,00 | PCWC | |
|* 22 | TABLE ACCESS FULL | DMTD001_VERSOES | 1 | 42 | 2 (0)| 00:00:01 | Q1,00 | PCWP | |
|* 23 | INDEX RANGE SCAN | DMTF020_MOROS_INDEX2 | 21 | | 1 (0)| 00:00:01 | Q2,02 | PCWP | |
|* 24 | TABLE ACCESS BY INDEX ROWID| DMTF020_MOROS | 125 | 9750 | 3 (0)| 00:00:01 | Q2,02 | PCWP | |
----------------------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("MOROS"."COD_PAIS"="PAIS_BST")
7 - filter("GRUPO_PAIS"='RESTO UNIAO EUROPEIA' AND "DTEND_VER"='9999-12-31 00:00')
8 - access("MOROS"."COD_NATJUR"="CNATJUR")
12 - filter("DESCRICAO"='Particulares' AND "DTEND_VER"='9999-12-31 00:00')
16 - filter("TIPO_GAR2"='GAR DINERARIA' AND "TIPO_GAR"='GAR REAL' AND "FLAG_PRIORIDADE"=1 AND "IDVERSAO"= (SELECT
MAX(SYS_OP_CSR(SYS_OP_MSR(MAX("IDVERSAO")),0)) FROM "RE_DM"."DMTD001_VERSOES" "DMTD001_VERSOES" WHERE
"TABELA"='RE_DM.DMTD002_GAR_CONTRATO' AND "DTEND_VER"='9999-12-31 00:00'))
22 - filter("TABELA"='RE_DM.DMTD002_GAR_CONTRATO' AND "DTEND_VER"='9999-12-31 00:00')
23 - access("MOROS"."CREFERENCIA"="CREFERENCIA_IMP")
filter("MOROS"."CREFERENCIA" IS NOT NULL)
24 - filter("MOROS"."IDVERSAO"=167 AND "MOROS"."CCONTA" IS NOT NULL AND TO_NUMBER("MOROS"."FLAG_MOROSIDADE")=0 AND
"MOROS"."INPUT"='IMP' AND "MOROS"."SEGMENTO"<>'GA' AND "MOROS"."SEGMENTO"<>'G1' AND "MOROS"."SEGMENTO"<>'PC' AND
"MOROS"."SEGMENTO"<>'G2' AND "MOROS"."SEGMENTO"<>'G3' AND "MOROS"."SEGMENTO"<>'LO' AND "MOROS"."CCONTA"="CCONTA")
Note
-----
- dynamic sampling used for this statement (level=5)
- Degree of Parallelism is 4 because of hint
Does anyone see something fishy with this "explain plan"? I've added indexes, I ran statistics, rebuild indexes... the server is a laptop with 8gb ram, SSD hard drive and i7 cpu.
Any ideas?

Answer 1

Obviously, look for your full table scans, but they aren't always the culprit. The problem appears to be in the nested loops.
I would focus on DMTD002_GAR_CONTRATO, and perhaps place an index to eliminate the
full table scan; however, I suspect that the main problem may be in the subquery in the where clause that creates table alias "GAR".
It would be worth experimenting with a hardcoded value rather than a subquery to see if it improves performance.

Answer 2

(Posted on behalf of OP).
Our temp tablespace was super tiny. After increasing the size all things start to go faster and smoother. Thanks to all that helped.