RE: Exadata Tuning Question+

From: Iggy Fernandez <iggy_fernandez_at_hotmail.com>
Date: Tue, 11 Nov 2014 04:28:55 -0800
Message-ID: <BLU179-W399C6710C6FC738B0DBC30EB810_at_phx.gbl>

Reposting since my reply was not posted
Abdul,
I cannot understand why the number of rows exploded from 21 million to 206 million in line 2. Surely, the number of rows cannot be more 21M because SID is (or appears to be) the primary key of SERVICE_LOOKUP and has a foreign key relationship to with SERVICE_RELATIONSHIP. Perhaps, primary key and foreign key constraints are not being enforced. I need to review the join conditions in the predicate section of the query plan. Because of the rows explosion, the required sort area size is 10G. You can try increasing the sort_area_size to 10G. A better strategy might be to perform the group by before the join using the WITH CLAUSE or the PLACE_GROUP_BY hint. Could you post the following two EXPLAIN PLAN (including the predicate sections) EXPLAIN PLAN FORSELECT slv.sid, slv.service_location_id, RTRIM(XMLSERIALIZE(CONTENT EXTRACT( XMLAGG(XMLELEMENT("e", DECODE(sr.relationship_level, '1', sr.RELATED_SID || ',', NULL)) ORDER BY sr.RELATED_SID), '//text()' )) , ',' ) AS relatedserviceinstanceidlevel1, RTRIM(XMLSERIALIZE(CONTENT EXTRACT( XMLAGG(XMLELEMENT("e", DECODE(sr.relationship_level, '2', sr.RELATED_SID || ',', NULL)) ORDER BY sr.RELATED_SID), '//text()' )) , ',' ) AS relatedserviceinstanceidlevel1, RTRIM(XMLSERIALIZE(CONTENT EXTRACT( XMLAGG(XMLELEMENT("e", DECODE(sr.relationship_level, '3', sr.RELATED_SID || ',', NULL)) ORDER BY sr.RELATED_SID), '//text()' )) , ',' ) AS relatedserviceinstanceidlevel1, RTRIM(XMLSERIALIZE(CONTENT EXTRACT( XMLAGG(XMLELEMENT("e", DECODE(sr.relationship_level, '4', sr.RELATED_SID || ',', NULL)) ORDER BY sr.RELATED_SID), '//text()' )) , ',' ) AS relatedserviceinstanceidlevel1, RTRIM(XMLSERIALIZE(CONTENT EXTRACT( XMLAGG(XMLELEMENT("e", DECODE(sr.relationship_level, '5', sr.RELATED_SID || ',', NULL)) ORDER BY sr.RELATED_SID), '//text()' )) , ',' ) AS relatedserviceinstanceidlevel1FROM service_lookup slv LEFT OUTER JOIN service_location sl ON sl.service_location_id = slv.service_location_id LEFT OUTER JOIN service_relationship sr ON sr.sid = slv.sid AND sr.relationship_level IN ('1', '2', '3', '4', '5')GROUP BY slv.id, slv.service_location_id; EXPLAIN PLAN FORWITH sr AS ( SELECT sr.id, LISTAGG(DECODE(sr.relationship_level, '1', sr.related_sid, NULL) ',') WITHIN GROUP (ORDER BY sr.related_sid) AS relatedserviceinstanceidlevel1, LISTAGG(DECODE(sr.relationship_level, '2', sr.related_sid, NULL) ',') WITHIN GROUP (ORDER BY sr.related_sid) AS relatedserviceinstanceidlevel2, LISTAGG(DECODE(sr.relationship_level, '3', sr.related_sid, NULL) ',') WITHIN GROUP (ORDER BY sr.related_sid) AS relatedserviceinstanceidlevel3, LISTAGG(DECODE(sr.relationship_level, '4', sr.related_sid, NULL) ',') WITHIN GROUP (ORDER BY sr.related_sid) AS relatedserviceinstanceidlevel4, LISTAGG(DECODE(sr.relationship_level, '5', sr.related_sid, NULL) ',') WITHIN GROUP (ORDER BY sr.related_sid) AS relatedserviceinstanceidlevel5 WHERE sr.relationship_level IN ('1', '2', '3', '4', '5') GROUP BY sr.id)SELECT slv.sid, slv.service_location_id, sr.relatedserviceinstanceidlevel1, sr.relatedserviceinstanceidlevel2, sr.relatedserviceinstanceidlevel3, sr.relatedserviceinstanceidlevel4, sr.relatedserviceinstanceidlevel5FROM service_lookup slv LEFT OUTER JOIN service_location sl ON sl.service_location_id = slv.service_location_id LEFT OUTER JOIN sr ON sr.sid = slv.sid;

From: Abdul.Ebadi_at_Level3.com

Thanks for the reply Iggy…
 
Your second suggestion below runs faster, but according to our developer we “cannot use LISTAGG as the string is larger than
 4000 chars for some of the values, so will have to use XMLAGG”
The first suggestion is OK and missing a group by, but when we added group by it didn’t finish even after long time.
 
Here is the plan for your second option (even switching to SORT MERGE join resulted in same thing – not finished):
 
Plan hash value: 4110902776
 
-------------------------------------------------------------------------------------------------------------
| Id  | Operation                    | Name                 | Rows  | Bytes |TempSpc| Cost (%CPU)| Time     |
-------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |                      |   206M|  9067M|       |   151K  (1)| 00:00:06 |
|   1 |  SORT GROUP BY               |                      |   206M|  9067M|    10G|   151K  (1)| 00:00:06 |
|*  2 |   HASH JOIN OUTER            |                      |   206M|  9067M|       |  2311   (7)| 00:00:01 |
|*  3 |    HASH JOIN                 |                      |  6539K|   149M|       |  1864   (4)| 00:00:01 |
|   4 |     TABLE ACCESS STORAGE FULL| SERVICE_LOCATION     |  3175K|    18M|       |   357   (1)| 00:00:01 |
|*  5 |     TABLE ACCESS STORAGE FULL| SERVICE_LOOKUP       |  6539K|   112M|       |  1503   (4)| 00:00:01 |
 
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|*  6 |    TABLE ACCESS STORAGE FULL | SERVICE_RELATIONSHIP |    21M|   454M|       |   376   (8)| 00:00:01 |
-------------------------------------------------------------------------------------------------------------
 
Thanks,
Abdul










 		 	   		   		 	   		  

--
http://www.freelists.org/webpage/oracle-l

Received on Tue Nov 11 2014 - 13:28:55 CET