RE: Table update is taking too much time

From: Deas, Scott <Scott.Deas_at_lfg.com>
Date: Sun, 29 May 2016 22:17:26 +0000
Message-ID: <C1FB7BA65B13C542B2CB1CE5DB8F74AF35F5DE6E_at_NC2PWEX501.us.ad.lfg.com>

Ashoke,

I assume you have some sort of maintenance window allocated for this work, so my recommendation would be to not do the update in place, but rather to do something like the following:

1. CTAS for each table you’re changing to create an empty copy of the table with the nologging option
2. Create a lookup table where you store original ut_id and new ut_id
3. Parallel, direct path insert from original table (joining to your control table to get the new ut_it) into new tables
4. Build all indexes/constraints
5. Verify data
6. Enable logging on tables/indexes
7. Rename objects so new tables now have the original table names

All of this assumes you aren’t changing in these objects.

You may also want to look at this whitepaper from Bryn Llewellyn that discusses using PL/SQL to transform one table into another, when it’s changing. https://blogs.oracle.com/plsql-and-ebr/resource/Transforming_One_Table_to_Another_Sql_or_Plsql_Whitepaper.pdf

Thanks,
Scott

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Ashoke Mandal Sent: Sunday, May 29, 2016 5:42 PM
To: ORACLE-L <oracle-l_at_freelists.org> Subject: Table update is taking too much time

Dear All, Let me know if you have any suggestions to make this update faster as six days is too high. Background: Due to some unexpected reason we have same set of test_ids in the table for two different testing facilities. We are trying to change the ut_ids of one facility to resolve the duplication issue using the following code. It works but taking 6 days to complete the update and looking for tips to make the update faster. The ut_id is part of the primary key in all three tables (master_table, child_table_1 and child_table_2).

 Records to be updated in master_table: 2437461 (total records in this table is 222760096)
Records to be updated in child_table_1: 370569916
Records to be updated in child_table_2: 4594843

Using following UNIX shell script and a stored procedure: => Calling shell script code:
export PATH=$PATH:/opt/bin:/usr/ccs/bin:/usr/sbin:/var/opt/oracle export DMAS_ROOT=/med_oracle/dmas/production export start_utid=$1
export end_utid=$2
export ORACLE_SID=$3

# Set oracle environment for the specified database ($3) export ORAENV_ASK=NO
. /usr/local/bin/oraenv

sqlplus user/password <<EOF1

• Disable the Foreign key constraints on the child tables ALTER TABLE CHILD_TABLE_1 DISABLE CONSTRAINT CHILD_TABLE_1_FK_UT_ID_TEST_DATE; ALTER TABLE CHILD_TABLE_2 DISABLE CONSTRAINT TEST_NOTE_FK_UT_ID_TEST_DATE;

TRUNCATE TABLE master_table_temp;
INSERT INTO master_table_temp select * from master_table where (ut_id>= ${start_utid} and ut_id <= ${end_utid}) and test_facility_code <> 'E';
-- Call the procedure to update the UT_Ids

   EXECUTE proc_update_utid ('$1','$2');

• Enable the foreign key constarints ALTER TABLE CHILD_TABLE_1 ENABLE NOVALIDATE CONSTRAINT child_table_1_FK_UT_ID_TEST_DATE; ALTER TABLE TEST_NOTE ENABLE NOVALIDATE CONSTRAINT child_table_2_FK_UT_ID_TEST_DATE;

   EXIT;
EOF1 => Called stored procedure
create or replace PROCEDURE proc_update_utid(start_utid number, end_utid number) AS

  lv_rec_count number :=0;
  lv_update_number number :=0;
  lv_total_rec_cnt number :=0;
  lv_last_utid number;
  lv_logfile varchar2(40);
  lv_db_name varchar2(8);
  lv_stmt varchar2(1000);

  output_file UTL_FILE.FILE_TYPE;

• Declare a cursor on the impacted records stored in the temporary working table cursor ut_cur is select * from master_table_temp order by ut_id;

begin
dbms_output.enable(10000000); -- setup of test output
-- Get the database name

select name into lv_db_name from v$database; lv_logfile := lv_db_name || '_' || 'update.log'; output_file := UTL_FILE.FOPEN('/med_oracle/dmas/production/log', lv_logfile, 'A');

utl_file.put_line(output_file,'Start Time: '|| to_char(sysdate, 'DD-MON-YYYY HH24:MI:SS'));

• Check the number of duplicate UT_IDs to be updated select count(*) into lv_total_rec_cnt from master_table where (ut_id >= start_utid and ut_id <= end_utid) and test_facility_code <> 'E'; utl_file.put_line(output_file,'Total number of duplicate UT_ID before the update: '|| lv_total_rec_cnt);
  --
  

   for ur_rec in ut_cur
   loop
-- dbms_output.put_line ('This is right before the update of unit_test table');

      update master_table set ut_id=ut_id+9000000000 where ut_id=ur_rec.ut_id and
      test_facility_code <> 'E';


--  dbms_output.put_line ('This is right before the update of child_table_1 table');


      update child_table_1 set ut_id=ut_id+9000000000 where child_table_1.ut_id=ur_rec.ut_id and
      test_date=ur_rec.test_date;
      update child_table_2 set ut_id=ut_id+9000000000 where child_table_2.ut_id=ur_rec.ut_id and
      test_date=ur_rec.test_date;
      test_date=ur_rec.test_date;
      lv_rec_count := lv_rec_count+1;
      if lv_rec_count = 1000
      then
        lv_update_number := lv_update_number+1;
      -- insert a row to the update_status table
        insert into update_status values(lv_update_number, ur_rec.ut_id, sysdate);
        commit;
        lv_rec_count := 0;
      else
        lv_last_utid := ur_rec.ut_id;
      end if;

   end loop;

• Following code is to address the last set of rows, which are less than 1000. if lv_rec_count != 1000 then lv_update_number := lv_update_number+1;
  • insert a row to the update_status table insert into update_status values(lv_update_number, lv_last_utid, sysdate);
    • dbms_output.put_line ('This is right before the second commit'); commit; end if;
      -- Verify if the UT_ID between start_utid and end_utid range with facility_code <> 'E' are
      
      • all assigned to a different UT_ID. If that is true then the following query shouldn't return any row. select count(*) into lv_total_rec_cnt from master_table where (ut_id >= start_utid and ut_id <= end_utid) and test_facility_code <> 'E'; dbms_output.put_line ('The total duplicate UT_IDs in master_table is ' ||lv_total_rec_cnt);
        --
        utl_file.put_line(output_file,'Total number of duplicate UT_ID after the update: '|| lv_total_rec_cnt);

utl_file.put_line(output_file,'End Time: '|| to_char(sysdate, 'DD-MON-YYYY HH24:MI:SS')); utl_file.fclose(output_file);

end proc_update_utid;

Thanks,
Ashoke
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http://www.freelists.org/webpage/oracle-l Received on Mon May 30 2016 - 00:17:26 CEST