Re: PostgreSQL Developer Best Practices - Mailing list pgsql-general
| From | Allan Kamau |
|---|---|
| Subject | Re: PostgreSQL Developer Best Practices |
| Date | |
| Msg-id | CAF3N6oSKe6T3MH=o3DLXXAsb1Lq2ATM=16kYvwB1HgANkFWSSQ@mail.gmail.com Whole thread Raw |
| In response to | Re: PostgreSQL Developer Best Practices (rob stone <floriparob@gmail.com>) |
| Responses |
Re: PostgreSQL Developer Best Practices
|
| List | pgsql-general |
On Wed, Aug 26, 2015 at 5:23 AM, rob stone <floriparob@gmail.com> wrote:
On Tue, 2015-08-25 at 20:17 -0400, Melvin Davidson wrote:
> I think a lot of people here are missing the point. I was trying to
> give examples of natural keys, but a lot of people are taking great
> delight
> in pointing out exceptions to examples, rather than understanding the
> point.
> So for the sake of argument, a natural key is something that in
> itself is unique and the possibility of a duplicate does not exist.
> Before ANYONE continues to insist that a serial id column is good,
> consider the case where the number of tuples will exceed a bigint.
> Don't say it cannot happen, because it can.
> However, if you have an alphanumeric field, let's say varchar 50, and
> it's guaranteed that it will never have a duplicate, then THAT is a
> natural primary
> key and beats the hell out of a generic "id" field.
>
> Further to the point, since I started this thread, I am holding to it
> and will not discuss "natural primary keys" any further.
>
> Other suggestions for good PostgreSQL Developer database (not web
> app) guidelines are still welcome.
>
Funny how Melvin's attempt to bring order to the chaos ended up as a
discussion about primary keys.
We once hired a "genius" to design an application to handle fixed
assets. Every table had a primary key named "id". Some were integer and
some were character. So the foreign key columns in child tables had to
be named differently. Writing the joins was complex.
I also know of an airline reservation system where you are unable to
alter your e-mail address. It apparently needs a DBA type person to
make the change. I can only guess that your e-mail address is used as a
foreign key in one or more tables. As well as assigning you a frequent
flyer number they also assign another integer identifier. A bit of
common sense goes a long way when designing an application.
Cheers,
rob
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I am in favour of using BIGINT "id" for the primary key in each table I create.
I found out that in the fields in my tables that I thought would be unique end up not being so in the longer term.
Also these values may need to be updated for some reason.
I have been using PRIMARY KEY(id) where id is of type BIGINT on each table I create.
I use a sequence to provide a default value to this field.
I create one such sequence DB object per table and the use it in the table definition.
For example if I have a sequenceDB "some_schema.some_table_seq" for table "some_schema.some_table".
In the table definition of "some_schema.some_table" I have the field "id" as follows.
id BIGINT NOT NULL DEFAULT NEXTVAL('some_schema.some_table_seq')
When I use this "id" field as a foreign key in another table, I would prefix it with the name of its parent table followed by a couple of underscores as shown below.
FOREIGN KEY(some_table__id)REFERENCES some_schema.some_table(id)ON UPDATE CASCADE ON DELETE CASCADE
For the composite keys that are unique (for now) I create a unique constraint.
Allan.
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