Re: Two academic questions

ср, 2 февр. 2022 г. в 09:19, David G. Johnston <david(dot)g(dot)johnston(at)gmail(dot)com>:

> On Tue, Feb 1, 2022 at 8:15 PM Дмитрий Иванов <firstdismay(at)gmail(dot)com>
> wrote:
>
>> Why are COLUMN GENERATED ALWAYS AS called "methods" and singled out as a
>> separate field type?
>>
>
> This sounds like you are describing something written. Can you provide a
> link to where that is?
>
> Is there a common name in the community for the approach in which the data
>> schema is presented as data?
>>
>
It is possible to give a link, but it would require authorization:
Here are the contents of the topic:
====================
Actual code include ALWAYS AS column:
CREATE TABLE bpd.schedules_calendar
(
id bigint NOT NULL DEFAULT
nextval('bpd.work_calendar_id_seq'::regclass),
work_date date NOT NULL,
work_year integer NOT NULL GENERATED ALWAYS AS (date_part('year'::text,
work_date)) STORED,
work_month integer NOT NULL GENERATED ALWAYS AS
(date_part('month'::text, work_date)) STORED,
work_day integer NOT NULL GENERATED ALWAYS AS (date_part('day'::text,
work_date)) STORED,
day_type bpd.day_type NOT NULL,
name_holiday character varying(100) COLLATE pg_catalog."default" NOT
NULL DEFAULT 'будний день'::character varying,
week40_day interval NOT NULL,
week40_month interval NOT NULL,
week36_day interval NOT NULL,
week36_month interval NOT NULL,
week35_day interval NOT NULL,
week35_month interval NOT NULL,
week24_day interval NOT NULL,
week24_month interval NOT NULL,
CONSTRAINT work_calendar_pkey PRIMARY KEY (id)
)
The code suggested in the studio:
CREATE TABLE "bpd"."schedules_calendar" (
"id" BigInt DEFAULT nextval('bpd.work_calendar_id_seq'::regclass) NOT
NULL,
"work_date" Date NOT NULL,
"work_year" Integer DEFAULT date_part('year'::text, work_date) NOT NULL,
"work_month" Integer DEFAULT date_part('month'::text, work_date) NOT
NULL,
"work_day" Integer DEFAULT date_part('day'::text, work_date) NOT NULL,
"day_type" "bpd"."day_type" NOT NULL,
"name_holiday" Character Varying( 100 ) DEFAULT 'будний
день'::character varying NOT NULL,
"week40_day" Interval NOT NULL,
"week40_month" Interval NOT NULL,
"week36_day" Interval NOT NULL,
"week36_month" Interval NOT NULL,
"week35_day" Interval NOT NULL,
"week35_month" Interval NOT NULL,
"week24_day" Interval NOT NULL,
"week24_month" Interval NOT NULL,
PRIMARY KEY ( "id" ) );

DEFAULT VALUE <> GENERATED ALWAYS AS STORED
the DEFAULT value is not recalculated when the reference column are
changed. is not an identical construction GENERATED ALWAYS AS STORED

*reply:*
They are in a separate list “Methods”.
This approach was used for other databases *long before* generated columns
were implemented in PostgreSQL.
====================

>
> Which community? There are many ways in which a "data schema [can be]
> presented as data". In PostgreSQL there is only a single source of truth
> for what the data schema is - the "System Catalogs" [1]. Those tables are
> made available to the user in the pg_catalog schema.
>
> David J.
>
>
I came across a long acronym defining the name of the approach, then I
decided that to come up with something fundamentally new is difficult
enough. That everything already has a formal name. But I can't find it
anymore. I need it to position my solution.
Shema - shema
Table Entity
id | propery1| property2| property3

Shema-data

Table Entity
id| name

Table Property Entity
id | id_entity | name| val

--
Regards, Dmitry!