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Thread: [PERFORM] Auto generate number in Postgres-9.1.

[PERFORM] Auto generate number in Postgres-9.1.

From

Dinesh Chandra 12108

Date:

20 March 2017, 19:38:40

Dear expert,

I have to add one column “ID” in postgres table which will generate Auto Incremented number .

Example:

Suppose I have five records and if I insert 1 new record It should auto generate 6.

If I truncate the same table and then again insert rows should start with 1 in “ID” column.

Regards,

Dinesh Chandra

|Database administrator (Oracle/PostgreSQL)| Cyient Ltd. Noida.

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This email message is for the sole use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message. Check all attachments for viruses before opening them. All views or opinions presented in this e-mail are those of the author and may not reflect the opinion of Cyient or those of our affiliates.

Re: [PERFORM] Auto generate number in Postgres-9.1.

From

Josh Berkus

Date:

20 March 2017, 19:43:11

Dinesh,

> I have to add one column  “ID” in postgres table which will generate
> Auto Increment
> <http://www.davidghedini.com/pg/entry/postgresql_auto_increment>ed number .
>
>
>
> Example:
>
> Suppose I have five records and if I insert 1 new record It should auto
> generate 6.

https://www.postgresql.org/docs/9.6/static/sql-createsequence.html
also SERIAL on this page:
https://www.postgresql.org/docs/9.6/static/datatype-numeric.html


>
> If I truncate the same table and then again insert rows should start
> with 1 in “ID” column.

That's not how it works, normally.  I'd suggest adding an ON TRUNCATE
trigger to the table.


--
Josh Berkus
Containers & Databases Oh My!

Re: [PERFORM] Auto generate number in Postgres-9.1.

From

Andreas Karlsson

Date:

20 March 2017, 19:48:23

On 03/20/2017 02:43 PM, Josh Berkus wrote:
>> If I truncate the same table and then again insert rows should start
>> with 1 in “ID” column.
>
> That's not how it works, normally.  I'd suggest adding an ON TRUNCATE
> trigger to the table.

Actually that may not be necessary as long as you make sure to use the
RESTART IDENTITY option when running TRUNCATE. I would argue that is a
cleaner solution than using triggers, if you can get away with it.

https://www.postgresql.org/docs/9.6/static/sql-truncate.html

Andreas

Re: [PERFORM] Auto generate number in Postgres-9.1.

From

John Gorman

Date:

20 March 2017, 19:50:06

Sequences are stored as a separate object in PostgreSQL.

Here in this example table and you can see that rec_id is a sequence number and that the object name is:
whiteboards_rec_id_seq

mydb=> \d whiteboards

                                         Table "public.whiteboards"
    Column     |            Type             |                          Modifiers
---------------+-----------------------------+--------------------------------------------------------------
 rec_id        | integer                     | not null default nextval('whiteboards_rec_id_seq'::regclass)
 board_name    | character varying(24)       | not null
 board_content | text                        | not null
 updatets      | timestamp without time zone | default now()
Indexes:
    "whiteboards_pkey" PRIMARY KEY, btree (rec_id)

Now I can display the whiteboards_rec_id_seq object

mydb=> \dS whiteboards_rec_id_seq
     Sequence "public.whiteboards_rec_id_seq"
    Column     |  Type   |         Value
---------------+---------+------------------------
 sequence_name | name    | whiteboards_rec_id_seq
 last_value    | bigint  | 12
 start_value   | bigint  | 1
 increment_by  | bigint  | 1
 max_value     | bigint  | 9223372036854775807
 min_value     | bigint  | 1
 cache_value   | bigint  | 1
 log_cnt       | bigint  | 31
 is_cycled     | boolean | f
 is_called     | boolean | t

-----Original Message-----
From: pgsql-performance-owner@postgresql.org [mailto:pgsql-performance-owner@postgresql.org] On Behalf Of Josh Berkus
Sent: Monday, March 20, 2017 6:43 AM
To: Dinesh Chandra 12108; pgsql-performance-owner@postgresql.org
Cc: pgsql-performance@postgresql.org
Subject: Re: [PERFORM] Auto generate number in Postgres-9.1.

Dinesh,

> I have to add one column  "ID" in postgres table which will generate
> Auto Increment
> <http://www.davidghedini.com/pg/entry/postgresql_auto_increment>ed number .
>
>
>
> Example:
>
> Suppose I have five records and if I insert 1 new record It should auto
> generate 6.

https://www.postgresql.org/docs/9.6/static/sql-createsequence.html
also SERIAL on this page:
https://www.postgresql.org/docs/9.6/static/datatype-numeric.html


>
> If I truncate the same table and then again insert rows should start
> with 1 in "ID" column.

That's not how it works, normally.  I'd suggest adding an ON TRUNCATE
trigger to the table.


--
Josh Berkus
Containers & Databases Oh My!


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Re: [PERFORM] Auto generate number in Postgres-9.1.

From

Dinesh Chandra 12108

Date:

20 March 2017, 20:08:07

Hi,

Thanks for your immediate response!!!!

Its working fine when we insert a new row.

But on deletion it's not automatically re-adjusting the id's.

Do I need to create trigger for this??

Regards,
Dinesh Chandra
|Database administrator (Oracle/PostgreSQL)| Cyient Ltd. Noida.


-----Original Message-----
From: pgsql-performance-owner@postgresql.org [mailto:pgsql-performance-owner@postgresql.org] On Behalf Of John Gorman
Sent: 20 March, 2017 7:20 PM
To: pgsql-performance@postgresql.org; pgsql-performance-owner@postgresql.org
Subject: Re: [PERFORM] Auto generate number in Postgres-9.1.

Sequences are stored as a separate object in PostgreSQL.

Here in this example table and you can see that rec_id is a sequence number and that the object name is:
whiteboards_rec_id_seq

mydb=> \d whiteboards

                                         Table "public.whiteboards"
    Column     |            Type             |                          Modifiers
---------------+-----------------------------+--------------------------
---------------+-----------------------------+--------------------------
---------------+-----------------------------+----------
 rec_id        | integer                     | not null default nextval('whiteboards_rec_id_seq'::regclass)
 board_name    | character varying(24)       | not null
 board_content | text                        | not null
 updatets      | timestamp without time zone | default now()
Indexes:
    "whiteboards_pkey" PRIMARY KEY, btree (rec_id)

Now I can display the whiteboards_rec_id_seq object

mydb=> \dS whiteboards_rec_id_seq
     Sequence "public.whiteboards_rec_id_seq"
    Column     |  Type   |         Value
---------------+---------+------------------------
 sequence_name | name    | whiteboards_rec_id_seq
 last_value    | bigint  | 12
 start_value   | bigint  | 1
 increment_by  | bigint  | 1
 max_value     | bigint  | 9223372036854775807
 min_value     | bigint  | 1
 cache_value   | bigint  | 1
 log_cnt       | bigint  | 31
 is_cycled     | boolean | f
 is_called     | boolean | t

-----Original Message-----
From: pgsql-performance-owner@postgresql.org [mailto:pgsql-performance-owner@postgresql.org] On Behalf Of Josh Berkus
Sent: Monday, March 20, 2017 6:43 AM
To: Dinesh Chandra 12108; pgsql-performance-owner@postgresql.org
Cc: pgsql-performance@postgresql.org
Subject: Re: [PERFORM] Auto generate number in Postgres-9.1.

Dinesh,

> I have to add one column  "ID" in postgres table which will generate
> Auto Increment
> <http://www.davidghedini.com/pg/entry/postgresql_auto_increment>ed number .
>
>
>
> Example:
>
> Suppose I have five records and if I insert 1 new record It should
> auto generate 6.

https://www.postgresql.org/docs/9.6/static/sql-createsequence.html
also SERIAL on this page:
https://www.postgresql.org/docs/9.6/static/datatype-numeric.html


>
> If I truncate the same table and then again insert rows should start
> with 1 in "ID" column.

That's not how it works, normally.  I'd suggest adding an ON TRUNCATE trigger to the table.


--
Josh Berkus
Containers & Databases Oh My!


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________________________________

DISCLAIMER:

This email message is for the sole use of the intended recipient(s) and may contain confidential and privileged
information.Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended
recipient,please contact the sender by reply email and destroy all copies of the original message. Check all
attachmentsfor viruses before opening them. All views or opinions presented in this e-mail are those of the author and
maynot reflect the opinion of Cyient or those of our affiliates.

Re: [PERFORM] Auto generate number in Postgres-9.1.

From

Andreas Karlsson

Date:

20 March 2017, 21:40:50

On 03/20/2017 03:08 PM, Dinesh Chandra 12108 wrote:
> But on deletion it's not automatically re-adjusting the id's.
>
> Do I need to create trigger for this??

It is possible to do but I advice against adjusting the IDs on DELETE
due to to do so safely would require locking the entire table in the
trigger.

Note that serial columns will also get holes on ROLLBACK. In general I
think the right thing to do is accept that your ID columns can get a bit
ugly.

For example:

CREATE TABLE t (id serial);

INSERT INTO t DEFAULT VALUES;

BEGIN;

INSERT INTO t DEFAULT VALUES;

ROLLBACK;

INSERT INTO t DEFAULT VALUES;

Gives us the following data in the table:

  id
----
   1
   3
(2 rows)

Andreas