SQL merge and after insert or update on ... for each row fires too often?

Question

Hello,
there is a base table, which has a companion history table
- lets say USER_DATA & USER_DATA_HIST.
For each update on USER_DATA there has to be recorded the old condition of the USER_DATA record into the USER_DATA_HIST (insert new record)
- to have the history of changes to USER_DATA.
The first approach was to do the insert for the row trigger:
trigger user_data_tr_aiu after insert or update on user_data for each rowBut the performance was bad, because for a bulk update to USER_DATA, there have been individual inserts per records.
So i tried a trick:
Instead of doing the real insert into USER_DATA_HIST, i collect the USER_DATA_HIST data into a pl/sql collection first.
And later i do a bulk insert for the collection in the USER_DATA_HIST table with stmt trigger:
trigger user_data_tr_ra after insert or update on user_dataBut sometimes i recognize, that the list of entries saved in the pl/sql collection are more than my USER_DATA records being updated.
(BTW, for the update i use SQL merge, because it's driven by another table.)
As there is a uniq tracking_id in USER_DATA record, i could identify, that there are duplicates.
If i sort for the tracking_id and remove duplicate i get exactly the #no of records updated by the SQL merge.
So how comes, that there are duplicates?
I can try to make a sample 'sqlplus' program, but it will take some time.
But maybe somebody knows already about some issues here(?!)
- many thanks!
best regards,
Frank

Answer 1

Hello
Not sure really. Although it shouldn't take long to do a test case - it only took me 10 mins....
SQL>
SQL> create table USER_DATA
  2  (   id      number,
  3      col1    varchar2(100)
  4  )
  5  /
Table created.
SQL>
SQL> CREATE TABLE USER_DATA_HIST
  2  (   id      number,
  3      col1    varchar2(100),
  4      tmsp    timestamp
  5  )
  6  /
Table created.
SQL>
SQL> CREATE OR REPLACE PACKAGE pkg_audit_user_data
  2  IS
  3
  4      PROCEDURE p_Init;
  5
  6      PROCEDURE p_Log
  7      (   air_UserData        IN user_data%ROWTYPE
  8      );
  9
10      PROCEDURE p_Write;
11  END;
12  /
Package created.
SQL> CREATE OR REPLACE PACKAGE BODY pkg_audit_user_data
  2  IS
  3
  4      TYPE tt_UserData        IS TABLE OF user_data_hist%ROWTYPE INDEX BY BINARY_INTEGER;
  5
  6      pt_UserData             tt_UserData;
  7
  8      PROCEDURE p_Init
  9      IS
10
11      BEGIN
12
13
14          IF pt_UserData.COUNT > 0 THEN
15
16              pt_UserData.DELETE;
17
18          END IF;
19
20      END;
21
22      PROCEDURE p_Log
23      (   air_UserData        IN user_data%ROWTYPE
24      )
25      IS
26          ln_Idx              BINARY_INTEGER;
27
28      BEGIN
29
30          ln_Idx := pt_UserData.COUNT + 1;
31
32          pt_UserData(ln_Idx).id     := air_UserData.id;
33          pt_UserData(ln_Idx).col1   := air_UserData.col1;
34          pt_UserData(ln_Idx).tmsp   := SYSTIMESTAMP;
35
36      END;
37
38      PROCEDURE p_Write
39      IS
40
41      BEGIN
42
43          FORALL li_Idx IN INDICES OF pt_UserData
44              INSERT
45              INTO
46                  user_data_hist
47              VALUES
48                  pt_UserData(li_Idx);
49
50      END;
51  END;
52  /
Package body created.
SQL>
SQL> CREATE OR REPLACE TRIGGER preu_s_user_data BEFORE UPDATE ON user_data
  2  DECLARE
  3
  4  BEGIN
  5
  6      pkg_audit_user_data.p_Init;
  7
  8  END;
  9  /
Trigger created.
SQL> CREATE OR REPLACE TRIGGER preu_r_user_data BEFORE UPDATE ON user_data
  2  FOR EACH ROW
  3  DECLARE
  4
  5      lc_Row      user_data%ROWTYPE;
  6
  7  BEGIN
  8
  9      lc_Row.id   := :NEW.id;
10      lc_Row.col1 := :NEW.col1;
11
12      pkg_audit_user_data.p_Log
13      (   lc_Row
14      );
15
16  END;
17  /
Trigger created.
SQL> CREATE OR REPLACE TRIGGER postu_s_user_data AFTER UPDATE ON user_data
  2  DECLARE
  3
  4  BEGIN
  5
  6      pkg_audit_user_data.p_Write;
  7
  8  END;
  9  /
Trigger created.
SQL>
SQL>
SQL> insert
  2  into
  3      user_data
  4  select
  5      rownum,
  6      dbms_random.string('u',20)
  7  from
  8      dual
  9  connect by
10      level <=10
11  /
10 rows created.
SQL> select * from user_data
  2  /
        ID COL1
         1 GVZHKXSSJZHUSLLIDQTO
         2 QVNXLTGJXFUDUHGYKANI
         3 GTVHDCJAXLJFVTFSPFQI
         4 CNVEGOTDLZQJJPVUXWYJ
         5 FPOTZAWKMWHNOJMMIOKP
         6 BZKHAFATQDBUVFBCOSPT
         7 LAQAIDVREFJZWIQFUPMP
         8 DXFICIPCBCFTPAPKDGZF
         9 KKSMMRAQUORRPUBNJFCK
        10 GBLTFZJAOPKFZFCQPGYW
10 rows selected.
SQL> select * from user_data_hist
  2  /
no rows selected
SQL>
SQL> MERGE
  2  INTO
  3      user_data a
  4  USING
  5  (   SELECT
  6          rownum + 8 id,
  7          dbms_random.string('u',20) col1
  8      FROM
  9          dual
10      CONNECT BY
11          level <= 10
12  ) b
13  ON (a.id = b.id)
14  WHEN MATCHED THEN
15      UPDATE SET a.col1 = b.col1
16  WHEN NOT MATCHED THEN
17      INSERT(a.id,a.col1)
18      VALUES (b.id,b.col1)
19  /
10 rows merged.
SQL> select * from user_data_hist
  2  /
        ID COL1                 TMSP
         9 XGURXHHZGSUKILYQKBNB 05-AUG-11 10.04.15.577989
        10 HLVUTUIFBAKGMXBDJTSL 05-AUG-11 10.04.15.578090
SQL> select * from v$version
  2  /
BANNER
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bi
PL/SQL Release 10.2.0.4.0 - Production
CORE    10.2.0.4.0      Production
TNS for Linux: Version 10.2.0.4.0 - Production
NLSRTL Version 10.2.0.4.0 - ProductionHTH
David