Re: Snippets?

On 5/24/19 12:24 PM, Ron wrote:
> On 5/24/19 1:27 PM, Adrian Klaver wrote:
>> On 5/24/19 11:15 AM, Ken Lacrosse wrote:
>>> Is there any way in postgresql to have a "snippet" of SQL code which
>>> you could apply to all tables. Something you could add which would
>>> ensure that every table always has a Created, Changed and Deleted
>>> column for example. Sort of like a C include I suppose.  Of course if
>>> I’m building a DB schema by hand I could just copy and paste those
>>> columns but it still seems a bit too, darn humans!, error prone.
>>
>> Not that I know of.
>>
>> Things I have done:
>> 1) Template table that I includes those fields that I then add to.
>>
>> FYI the Sqitch schema management system allows you to do the above:
>> https://sqitch.org/docs/manual/sqitch-add/#templates
>>
>> 2) A script that I run over table definition to add the fields.
>
> What about INHERITS?

It is an option, though it does have baggage:
https://www.postgresql.org/docs/11/sql-createtable.html
"INHERITS ( parent_table [, ... ] )

The optional INHERITS clause specifies a list of tables from which
the new table automatically inherits all columns. Parent tables can be
plain tables or foreign tables.

Use of INHERITS creates a persistent relationship between the new
child table and its parent table(s). Schema modifications to the
parent(s) normally propagate to children as well, and by default the
data of the child table is included in scans of the parent(s).

..."""

There is more.

If I was to go that route I would use LIKE:

"LIKE source_table [ like_option ... ]

The LIKE clause specifies a table from which the new table
automatically copies all column names, their data types, and their
not-null constraints.

Unlike INHERITS, the new table and original table are completely
decoupled after creation is complete. Changes to the original table will
not be applied to the new table, and it is not possible to include data
of the new table in scans of the original table.

..."

>
> test=# create table CCD_template (
> test(#  Created timestamptz,
> test(#  Changed timestamptz,
> test(#  Deleted timestamptz );
> CREATE TABLE
>
> test=# create table foobar (
>   field1 integer,
>   field2 bytea
> ) inherits (CCD_template);
> CREATE TABLE
> test=#
> test=# \d foobar
>              Table "public.foobar"
>  Column  |           Type           | Modifiers
> ---------+--------------------------+-----------
>  created | timestamp with time zone |
>  changed | timestamp with time zone |
>  deleted | timestamp with time zone |
>  field1  | integer                  |
>  field2  | bytea                    |
> Inherits: ccd_template
>
>
>>
>>>
>>> Ken LaCrosse
>>>
>>> Senior IT InfoSec and Infrastructure Monitoring Specialist
>>>
>>> I.T. | American Recovery Service & Skipbusters
>>>
>>> Phone: (800)398-6480 x3758
>>>
>>> Email: KLacrosse(at)pkwillis(dot)com <mailto:KLacrosse(at)pkwillis(dot)com>
>>>
>>> www.pkwillis.com <http://www.pkwillis.com/>
>>>
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>>
>>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com