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Getting the first 10 unused manual_sequence numbers

I would like to find the first 10 unused manual sequence numbers from the range.

Please find my request below:

select X1.* From
    (Select Rownum seq_number From Dual Connect By Rownum <= 
         (Select LPAD(9,(UTC.DATA_PRECISION - UTC.DATA_SCALE),9) 
          From User_Tab_Columns UTC 
          where UTC.Table_Name = 'Table_Name' And UTC.Column_Name = 'seq_number')) X1,
Table_Name X2
Where X1.seq_number = X2.seq_number (+)
  And X2.Rowid is Null
  And Rownum <= 10

Although it gives the desired result, I am worried about the download caused by [if any], because we will use this request several times a day.

Please advise if there is a way to optimize this query.

Additional Information: Table_Name T2 has a unique index defined in (seq_number)

Work example:

create table TEMP_TABLE_NAME ( seq_number number(6))

insert into TEMP_TABLE_NAME 
select distinct trunc(dbms_random.VALUE(1,5000)) seq_number 
from dual
connect by rownum <= 1000


create unique index TEMP_TABLE_NAME_IDX on TEMP_TABLE_NAME(seq_Number)


SELECT T1.*
  FROM (    SELECT ROWNUM seq_number
              FROM DUAL
        CONNECT BY ROWNUM <=
                      (SELECT LPAD (9,(UTC.DATA_PRECISION - UTC.DATA_SCALE),9)
                         FROM User_Tab_Columns UTC
                        WHERE     UTC.Table_Name = 'TEMP_TABLE_NAME'
                              AND UTC.Column_Name = 'SEQ_NUMBER')) T1,
       TEMP_TABLE_NAME T2
 WHERE     T1.seq_number = T2.seq_number(+)
       AND T2.ROWID IS NULL
       AND ROWNUM <= 10

For me, my query gave the result below. The randomly generated numbers in the table included 7 and 8, so they were ignored. The point is to get the first 10 unused numbers.

1
2
3
4
5
6
9
10
11
12
+4
source share
1

:

Select Rownum seq_number From Dual Connect By Rownum <= 
         (Select LPAD(9,(UTC.DATA_PRECISION - UTC.DATA_SCALE),9) 
          From User_Tab_Columns UTC 
          where UTC.Table_Name = 'Table_Name' And UTC.Column_Name = 'seq_number')

:

Select Rownum As seq_number From Dual 
Connect By Rownum <= (Select max( seq_number ) + 10 From TEMP_TABLE_NAME )

:

Select Rownum As seq_number From Dual Connect By Rownum <= 1000000

:

create table TEMP_TABLE_NAME(
  seq_number NUMBER
);

SELECT LPAD (9,(UTC.DATA_PRECISION - UTC.DATA_SCALE),9) as x , 
       UTC.DATA_PRECISION, UTC.DATA_SCALE, UTC.COLUMN_NAME
FROM User_Tab_Columns UTC
WHERE     UTC.Table_Name = 'TEMP_TABLE_NAME'
  AND UTC.Column_Name = 'SEQ_NUMBER'
;

X        DATA_PRECISION DATA_SCALE COLUMN_NAME
-------- -------------- ---------- -----------
  (null)         (null)     (null) SEQ_NUMBER

:

create table TEMP_TABLE_NAME(
  seq_number NUMBER(15,0)
);

999999999999999,

SELECT count(*) FROM (
 SELECT ROWNUM seq_number
              FROM DUAL
        CONNECT BY ROWNUM <=
                      (SELECT LPAD (9,(UTC.DATA_PRECISION - UTC.DATA_SCALE),9)
                         FROM User_Tab_Columns UTC
                        WHERE     UTC.Table_Name = 'TEMP_TABLE_NAME'
                              AND UTC.Column_Name = 'SEQ_NUMBER')
);

ORA-30009: Not enough memory for CONNECT BY operation
30009. 0000 -  "Not enough memory for %s operation"
*Cause:    The memory size was not sufficient to process all the levels of the
           hierarchy specified by the query.
*Action:   In WORKAREA_SIZE_POLICY=AUTO mode, set PGA_AGGREGATE_TARGET to
           a reasonably larger value.
           Or, in WORKAREA_SIZE_POLICY=MANUAL mode, set SORT_AREA_SIZE to a
           reasonably larger value.

-, !!!
, ORDER BY.
→ - ORDER BY

ORDER BY - . , . , ORDER BY SELECT, .

:

create table TEMP_TABLE_NAME 
as SELECT * FROM (
    select rownum as seq_number , t.*
    from ALL_OBJECTS t
    cross join ( select * from dual connect by level <= 10)
    where rownum <= 100000
)
ORDER BY DBMS_RANDOM.Value;
create unique index TEMP_TABLE_NAME_IDX on TEMP_TABLE_NAME(seq_Number);

select count(*) from TEMP_TABLE_NAME;
  COUNT(*)
----------
    100000

DELETE FROM TEMP_TABLE_NAME
WHERE seq_number between 10000 and 10002
  OR seq_number between 20000 and 20002
  OR seq_number between 30000 and 30002
  OR seq_number between 40000 and 40002
  OR seq_number between 50000 and 50002
  OR seq_number between 60000 and 60002
  ;

, :

SELECT T1.*
  FROM (    SELECT ROWNUM seq_number
              FROM DUAL
        CONNECT BY ROWNUM <= 1000000
) T1,
       TEMP_TABLE_NAME T2
 WHERE     T1.seq_number = T2.seq_number(+)
       AND T2.ROWID IS NULL
       AND ROWNUM <= 10
;

SEQ_NUMBER
----------
     10000
     10001
     10002
     20000
     20001
     20002
     30000
     30001
     30002
     40000

, - - , ?
: ORDER BY . :

SELECT /*+ NO_INDEX(T2) */ T1.*
  FROM (    SELECT ROWNUM seq_number
              FROM DUAL
        CONNECT BY ROWNUM <= 1000000
) T1,
       TEMP_TABLE_NAME T2
 WHERE     T1.seq_number = T2.seq_number(+)
       AND T2.ROWID IS NULL
       AND ROWNUM <= 10
;

SEQ_NUMBER
----------
    213856
    910281
    668862
    412743
    295487
    214762
    788486
    346216
    777734
    806457

ORDER BY , .
ANSI SQL LEFT JOIN WHERE .... (+).

SELECT  * FROM (
    SELECT /*+ NO_INDEX(T2) */ T1.*
      FROM (    SELECT ROWNUM seq_number
                  FROM DUAL
            CONNECT BY ROWNUM <= 1000000
    ) T1 
    LEFT JOIN TEMP_TABLE_NAME T2
    ON T1.seq_number = T2.seq_number
    WHERE T2.ROWID IS NULL
    ORDER BY T1.seq_number
)
WHERE ROWNUM <= 10


- - 10 - 100 :

SET TIMING ON;
DECLARE
   x NUMBER;
BEGIN
   FOR i IN 1..10 LOOP
      SELECT sum( seq_number ) INTO x
      FROM (
           SELECT  * FROM (
            SELECT T1.*
              FROM (    SELECT ROWNUM seq_number
                          FROM DUAL
                    CONNECT BY ROWNUM <= 1000000
            ) T1 
            LEFT JOIN TEMP_TABLE_NAME T2
            ON T1.seq_number = T2.seq_number
            WHERE T2.ROWID IS NULL
            ORDER BY T1.seq_number
            )
            WHERE ROWNUM <= 10
        );
    END LOOP;
END;
/

PL/SQL procedure successfully completed.

Elapsed: 00:00:11.750

10 - 11,75 , 1,2 .

, CONNECT BY :

SET TIMING ON;
DECLARE
   x NUMBER;
BEGIN
   FOR i IN 1..10 LOOP
      SELECT sum( seq_number ) INTO x
      FROM (
           SELECT  * FROM (
            SELECT T1.*
              FROM (    SELECT ROWNUM seq_number
                          FROM DUAL
                    CONNECT BY ROWNUM <= (Select max( seq_number ) + 10 From TEMP_TABLE_NAME ) 
            ) T1 
            LEFT JOIN TEMP_TABLE_NAME T2
            ON T1.seq_number = T2.seq_number
            WHERE T2.ROWID IS NULL
            ORDER BY T1.seq_number
            )
            WHERE ROWNUM <= 10
        );
    END LOOP;
END;
/
PL/SQL procedure successfully completed.

Elapsed: 00:00:00.986

- 100 .
, CONNECT BY .

, 1 ( ) CONNECT BY, " " :

create table seq(
   seq_number int primary key
)
ORGANIZATION INDEX ;

INSERT INTO seq 
SELECT level FROM dual
CONNECT BY LEVEL <= 1000000;

SET TIMING ON;
DECLARE
   x NUMBER;
BEGIN
   FOR i IN 1..10 LOOP
      SELECT sum( seq_number ) INTO x
      FROM (
           SELECT  * FROM (
            SELECT T1.*
            FROM seq T1 
            LEFT JOIN TEMP_TABLE_NAME T2
            ON T1.seq_number = T2.seq_number
            WHERE T2.ROWID IS NULL
            ORDER BY T1.seq_number
            )
            WHERE ROWNUM <= 10
        );
    END LOOP;
END;
/

PL/SQL procedure successfully completed.

Elapsed: 00:00:00.398

- 40

- 1200 , - 40 - 30 (3000%).

+2

Source: https://habr.com/ru/post/1682018/

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