SQL Dev Data Modeller: Auto-generate Surrogate PKs in the Physical Model ?

Question

How can I have the logical modeller allow the user to design with logical PKs, but then have surrogate primary keys be auto-generated off sequences by the modeller when it comes to create the physical model - as in conventional application design?
Without this facility, this tool is useless, IMO.
I want:
i). sequences to become the physical PKs by default, and that what were the logical PKs in the logical model, to become a unique key in the physical model.
ii). I want this set by default when generating the physical model....
iii). ....with an option to turn this off on a entity-by-entity basis (as not all tables will necessarily require such a surrogate PK; so the logical PK may remain the physical PK).

Answer 1

It is common practice that physical PKs in Oracle tables are defined from sequences (surrogate PKs), and that the logical PK from the entity becomes a unique key in the table.
This may not always be the case in every application out there, and some people may disagree, but it is nonetheless a needed feature.
My new Feature Request is therefore:
I would like to see the following additions to the product.
1. In the Preferences -> Data Modeler -> Model -> Logical, a flag that by default indicates whether the designer wishes to opt to enable this feature (ie; have all logical PKs converted to unique keys, and replaced by sequence nos. in the physical model). This flags needs to be there since in real life, albeit erroneously IMO, some people will choose not to opt to use this functionality.
2. On every entity created in the model, there needs to be a flag that allows to override this default option, as not every table will require a surrogate PK to be generated. Being able to (re)set a flag located on the entity properties (perhaps under 'Engineer To'), will accomplish this.
3. When Forward Engineering to the physical model from the logical, the following should happen.
ENTITY  1 ---------->TABLE 1
---------------------> P * Surrogate PK
* Attribute 1 -----> U * Column 1
* Attribute 2 -----> U * Column 2
o Attribute 3 ----------> Column 3
Here you can see,
- Attributes 1 & 2 (the logical PK) of the entity become a unique key in the table (columns 1 & 2),
- optional Attribute 3 becomes NULLable column 3,
- and a physical surrogate PK column is added (type unbounded INTEGER, PRIMARY KEY constraint added).
From entity DEPT as:   (Examples based on SCOTT schema)
DEPTNO NUMBER(2) NOT NULL <-- Logical primary key on entity
DNAME VARCHAR2(14)
LOC VARCHAR2(13)
CREATE TABLE DEPT
(PK_DEPT INTEGER, -- New column becomes surrogate physical PK, driven from sequence defined later
DEPTNO NUMBER(2) NOT NULL, -- Former logical PK becomes a UK
DNAME VARCHAR2(14),
LOC VARCHAR2(13))
ALTER TABLE DEPT
ADD CONSTRAINT PK_DEPT PRIMARY KEY (PK_DEPT) USING INDEX PCTFREE 0
ALTER TABLE DEPT
ADD CONSTRAINT UKLPK_DEPTNO UNIQUE (DEPTNO) USING INDEX PCTFREE 0 -- Former logical PK becomes a UK (constraint name reflects this)
CREATE SEQUENCE PK_DEPT_SEQ
CREATE TRIGGER PK_DEPT_SEQ_TRG
BEFORE INSERT ON DEPT
FOR EACH ROW
WHEN (new.PK_DEPT IS NULL)
BEGIN
SELECT PK_DEPT_SEQ.NEXTVAL
INTO :new.PK_DEPT
FROM DUAL;
-- Or from 11g onwards, simply,
:new.PK_DEPT := PK_DEPT_SEQ.NEXTVAL;
END;
From entity EMP as:
EMPNO NUMBER(4) NOT NULL -- Logical primary key on entity
ENAME VARCHAR2(10)
JOB VARCHAR2(9)
MGR NUMBER(4)
HIREDATE DATE
SAL NUMBER(7,2)
COMM NUMBER(7,2)
DEPTNO NUMBER(2)
CREATE TABLE EMP
(PK_EMP INTEGER, -- New column becomes surrogate physical PK, driven from sequence defined later
FK_DEPT INTEGER, -- New FK to surrogate PK in DEPT table (maybe NOT NULL depending on relationship with parent)
EMPNO NUMBER(4) NOT NULL, -- Former logical PK becomes a UK
ENAME VARCHAR2(10),
JOB VARCHAR2(9),
MGR NUMBER(4),
HIREDATE DATE,
SAL NUMBER(7,2),
COMM NUMBER(7,2),
DEPTNO NUMBER(2))
ALTER TABLE EMP
ADD CONSTRAINT PK_EMP PRIMARY KEY (PK_EMP) USING INDEX PCTFREE 0
ALTER TABLE EMP
ADD CONSTRAINT FK_DEPT FOREIGN KEY (FK_DEPT) REFERENCES DEPT (PK_DEPT)
ALTER TABLE EMP
ADD CONSTRAINT UKLPK_EMPNO UNIQUE (EMPNO) USING INDEX PCTFREE 0 -- Former logical PK becomes a UK (constraint name reflects this)
CREATE SEQUENCE PK_EMP_SEQ
CREATE TRIGGER PK_EMP_SEQ_TRG
BEFORE INSERT ON EMP
FOR EACH ROW
WHEN (new.PK_EMP IS NULL)
BEGIN
SELECT PK_EMP_SEQ.NEXTVAL
INTO :new.PK_EMP
FROM DUAL;
-- Or from 11g onwards, simply,
:new.PK_EMP := PK_EMP_SEQ.NEXTVAL;
END;
[NOTE:   I use PCTFREE 0 to define the index attributes for the primary & unique keys since the assumption is that they will in general not get updated, thereby allowing for the denser packing of entries in the indexes and the (albeit minor) advantages that go with it.
This is certainly always true of a sequence-driven primary key (as it is by its very nature immutable), but if the unique key is likely to be frequently updated, then this PCTFREE option could be user-configurable on a per table basis (perhaps under Table Properties -> unique Constraints).
For non-sequence-driven primary keys, this storage option could also appear under Table Properties -> Primary Key.
I notice no storage options exist in general for objects, so you may like to consider adding this functionality overall].
Associated Issues :
- Preferences, 'Naming Standard: Templates' should be updated to allow for the unique key/constraint to be called something different, thus highlighting that it comes from the logical PK. I've used 'UKLPK' in this example.
- Mark the physical PK as being generated from a sequence; perhaps a flag under Table Properties -> Primary Key.
- When Forward Engineering, if an entity exists without a logical PK, the forward engineering process should halt with a fatal error.
!!! MODERATOR PLEASE DELETE ME !!!