SQL Update statement taking too long..

Question

Hi All,
I have a simple update statement that goes through a table of 95000 rows that is taking too long to update; here are the details:
Oracle Version: 11.2.0.1 64bit
OS: Windows 2008 64bit
desc temp_person;
Name                                                                                Null?    Type
PERSON_ID                                                                           NOT NULL NUMBER(10)
DISTRICT_ID                                                                     NOT NULL NUMBER(10)
FIRST_NAME                                                                                   VARCHAR2(60)
MIDDLE_NAME                                                                                  VARCHAR2(60)
LAST_NAME                                                                                    VARCHAR2(60)
BIRTH_DATE                                                                                   DATE
SIN                                                                                          VARCHAR2(11)
PARTY_ID                                                                                     NUMBER(10)
ACTIVE_STATUS                                                                       NOT NULL VARCHAR2(1)
TAXABLE_FLAG                                                                                 VARCHAR2(1)
CPP_EXEMPT                                                                                   VARCHAR2(1)
EVENT_ID                                                                            NOT NULL NUMBER(10)
USER_INFO_ID                                                                                 NUMBER(10)
TIMESTAMP                                                                           NOT NULL DATE
CREATE INDEX tmp_rs_PERSON_ED ON temp_person (PERSON_ID,DISTRICT_ID) TABLESPACE D_INDEX;
Index created.
ANALYZE INDEX tmp_PERSON_ED COMPUTE STATISTICS;
Index analyzed.
explain plan for update temp_person
  2  set first_name = (select trim(f_name)
  3                    from ext_names_csv
  4                               where temp_person.PERSON_ID=ext_names_csv.p_id
  5                               and   temp_person.DISTRICT_ID=ext_names_csv.ed_id);
Explained.
@?/rdbms/admin/utlxpls.sql
PLAN_TABLE_OUTPUT
Plan hash value: 3786226716
| Id  | Operation                   | Name           | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | UPDATE STATEMENT            |                | 82095 |  4649K|  2052K  (4)| 06:50:31 |
|   1 |  UPDATE                     | TEMP_PERSON    |       |       |            |          |
|   2 |   TABLE ACCESS FULL         | TEMP_PERSON    | 82095 |  4649K|   191   (1)| 00:00:03 |
|*  3 |   EXTERNAL TABLE ACCESS FULL| EXT_NAMES_CSV  |     1 |   178 |    24   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   3 - filter("EXT_NAMES_CSV"."P_ID"=:B1 AND "EXT_NAMES_CSV"."ED_ID"=:B2)
Note
   - dynamic sampling used for this statement (level=2)
19 rows selected.By the looks of it the update is going to take 6 hrs!!!
ext_names_csv is an external table that have the same number of rows as the PERSON table.
ROHO@rohof> desc ext_names_csv
Name                                                                                Null?    Type
P_ID                                                                                         NUMBER
ED_ID                                                                                        NUMBER
F_NAME                                                                                       VARCHAR2(300)
L_NAME                                                                                       VARCHAR2(300)Anyone can help diagnose this please.
Thanks
Edited by: rsar001 on Feb 11, 2011 9:10 PM

Answer 1

Thank you all for the great ideas, you have been extremely helpful. Here is what we did and were able to resolve the query.
We started with Etbin's idea to create a table from the ext table so that we can index and reference easier than an external table, so we did the following:
SQL> create table ext_person as select P_ID,ED_ID,trim(F_NAME) fst_name,trim(L_NAME) lst_name from EXT_NAMES_CSV;
Table created.
SQL> desc ext_person
Name                                                                                Null?    Type
P_ID                                                                                         NUMBER
ED_ID                                                                                        NUMBER
FST_NAME                                                                                     VARCHAR2(300)
LST_NAME                                                                                     VARCHAR2(300)
SQL> select count(*) from ext_person;
  COUNT(*)
     93383
SQL> CREATE INDEX EXT_PERSON_ED ON ext_person (P_ID,ED_ID) TABLESPACE D_INDEX;
Index created.
SQL> exec dbms_stats.gather_index_stats(ownname=>'APPD', indname=>'EXT_PERSON_ED',partname=> NULL , estimate_percent=> 30 );
PL/SQL procedure successfully completed.We had a look at the plan with the original SQL query that we had:
SQL> explain plan for update temp_person
  2  set first_name = (select fst_name
  3                    from ext_person
  4                               where temp_person.PERSON_ID=ext_person.p_id
  5                               and   temp_person.DISTRICT_ID=ext_person.ed_id);
Explained.
SQL> @?/rdbms/admin/utlxpls.sql
PLAN_TABLE_OUTPUT
Plan hash value: 1236196514
| Id  | Operation                    | Name           | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | UPDATE STATEMENT             |                | 93383 |  1550K|   186K (50)| 00:37:24 |
|   1 |  UPDATE                      | TEMP_PERSON    |       |       |            |          |
|   2 |   TABLE ACCESS FULL          | TEMP_PERSON    | 93383 |  1550K|   191   (1)| 00:00:03 |
|   3 |   TABLE ACCESS BY INDEX ROWID| EXTT_PERSON    |     9 |  1602 |     1   (0)| 00:00:01 |
|*  4 |    INDEX RANGE SCAN          | EXT_PERSON_ED  |     1 |       |     1   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   4 - access("EXT_PERSON"."P_ID"=:B1 AND "RS_PERSON"."ED_ID"=:B2)
Note
   - dynamic sampling used for this statement (level=2)
20 rows selected.As you can see the time has dropped to 37min (from 6 hrs). Then we decided to change the SQL query and use donisback's suggestion (using MERGE); we explained the plan for teh new query and here is the results:
SQL> explain plan for MERGE INTO temp_person t
  2  USING (SELECT fst_name ,p_id,ed_id
  3  FROM  ext_person) ext
  4  ON (ext.p_id=t.person_id AND ext.ed_id=t.district_id)
  5  WHEN MATCHED THEN
  6  UPDATE set t.first_name=ext.fst_name;
Explained.
SQL> @?/rdbms/admin/utlxpls.sql
PLAN_TABLE_OUTPUT
Plan hash value: 2192307910
| Id  | Operation            | Name         | Rows  | Bytes |TempSpc| Cost (%CPU)| Time     |
|   0 | MERGE STATEMENT      |              | 92307 |    14M|       |  1417   (1)| 00:00:17 |
|   1 |  MERGE               | TEMP_PERSON  |       |       |       |            |          |
|   2 |   VIEW               |              |       |       |       |            |          |
|*  3 |    HASH JOIN         |              | 92307 |    20M|  6384K|  1417   (1)| 00:00:17 |
|   4 |     TABLE ACCESS FULL| TEMP_PERSON  | 93383 |  5289K|       |   192   (2)| 00:00:03 |
|   5 |     TABLE ACCESS FULL| EXT_PERSON   | 92307 |    15M|       |    85   (2)| 00:00:02 |
Predicate Information (identified by operation id):
   3 - access("P_ID"="T"."PERSON_ID" AND "ED_ID"="T"."DISTRICT_ID")
Note
   - dynamic sampling used for this statement (level=2)
21 rows selected.As you can see, the update now takes 00:00:17 to run (need to say more?) :)
Thank you all for your ideas that helped us get to the solution.
Much appreciated.
Thanks