Oracle Partitioned Sequence - sql

Question

I'm trying to see if exists something to create a sequence with partition logic.
I need a sequence number that depend on other primary key ex:
id_person sequence id
1 | 1
1 | 2
2 | 1
3 | 1
1 | 3
so the sequence must depend on the id_person partition. Is there something like this on oracle or i must implement it by myself on the application level?
thank you.
Hi have create this PLSQL package one function and procedure:
PROCEDURE INIT_SEQUENCE(NAME varchar2, pkColumnNameList PARTITIONED_SEQUENCE_PK_COLUMN);
FUNCTION GET_NEXT_SEQUENCE_VALUE(NAME varchar2, pkPartitionColValue PARTITIONED_SEQUENCE_COL_VALUE) RETURN NUMBER;
INIT_SEQUENCE - get in input the name to associate at the sequence and a list of column name that are the fixed primary key part that vincolate the sequence Ex:'ID_PERSON'
the work of this procedure is to create the table that will manage the increment of sequence according to pkColumnNameList column.
GET_NEXT_SEQUENCE_VALUE- get the name of sequence to increment and the value of pkColumnNameList primary key and make the next step:
1) Create dynamically the sql to work
2) dbms_lock.allocate_unique(); to lock the table
3) check if is present a record in the table for pk value in input
4) if a record is present update the record with max + 1 in the sequence column
5) if a record is not present insert the new record with the 1 in the sequence column
6) return new id;
i would like to receive comment about this thanks in advance...

Answer 1

Is the actual requirement that the secondary sequence be gap free? If so, you've got a giant serialization/scalability issue.
If you need to present a gap-free sequence for human consumption, you could use an actual sequence (or a timestamp, for that matter) as Nick Pierpont suggests and preserve scalability, you could use analytic functions.
Dataset (t1):
ID_PERSON SEQUENCE_ID
---------- -----------
1 1
2 2
3 3
1 4
1 5
1 6
2 7
3 8
1 9
SQL:
select *
from
(select id_person,
sequence_id as orig_sequence_id,
rank ()
over (partition by id_person
order by sequence_id)
as new_sequence_id
from t1
)
order by id_person, new_sequence_id;
Result:
ID_PERSON ORIG_SEQUENCE_ID NEW_SEQUENCE_ID
---------- ---------------- ---------------
1 1 1
1 4 2
1 5 3
1 6 4
1 9 5
2 2 1
2 7 2
3 3 1
3 8 2

Answer 2

I'm afraid you have to do it like this:
INSERT INTO t
(
id_person,
sequence_id
)
VALUES
(
<your_person_id>,
( SELECT 1 + NVL( MAX( sequence_id ), 0 )
FROM t
WHERE t.id_person = <your_person_id>
)
)

Answer 3

What you are looking for is not a sequence, as the Oracle Documentation claims: "The sequence generator provides a sequential series of numbers".
You are looking for a calculated field depending on another, in this case the primary key. As other suggested you need to add the logic on your code. It means in a procedure or in the insert sentence.