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Re: Merging records in a table with 2-columns primary key - Mailing list pgsql-general

From	Alexander Farber
Subject	Re: Merging records in a table with 2-columns primary key
Date	April 2, 2017 21:27:28
Msg-id	CAADeyWj7K6V=E+rLNEksEtWjPVVc_2Rxkw3Mz=xmvY2vp8vC8Q@mail.gmail.com Whole thread Raw
In response to	Re: Merging records in a table with 2-columns primary key (Andy Colson <andy@squeakycode.net>)
List	pgsql-general

Hello Andy and others -

On Sun, Apr 2, 2017 at 5:13 PM, Andy Colson <andy@squeakycode.net> wrote:

On 04/02/2017 09:26 AM, Alexander Farber wrote:
http://stackoverflow.com/questions/43168406/merging-records-in-a-table-with-2-columns-primary-key

after some thinking, when I call

SELECT out_uid FROM merge_users(ARRAY[1,2,3,4]);

then "reviews" table should be empty (get rid of all self-reviews)

and "users" should contain just 1 record (1, 'User 1').

And if instead I call

SELECT out_uid FROM merge_users(ARRAY[1,2]);

then "reviews" should be (records with User 2 removed because overlapped with User 1):

uid | author | review

-----+--------+------------------------

1 | 3 | User 3 says: 1 is nice

1 | 4 | User 4 says: 1 is nice

3 | 1 | User 1 says: 3 is nice

3 | 4 | User 4 says: 3 is ugly

4 | 1 | User 1 says: 4 is ugly

4 | 3 | User 3 says: 4 is ugly

and "users":

uid | name

-----+--------

1 | User 1

3 | User 3

4 | User 4

So my 2 questions are -

1) Why the error when calling merge_users(ARRAY[1,2]) and then merge_users(ARRAY[1,2,3,4])?

2) Is there a way to use an UPDATE reviews instead of the inefficient (because copying) INSERT ... SELECT ... ON CONFLICT DO NOTHING?

Thank you

Alex

From: Andy Colson
Date: 02 April 2017, 21:13:07
Subject: Re: Merging records in a table with 2-columns primary key

From: Francisco Olarte
Date: 02 April 2017, 21:37:36
Subject: Re: Merging records in a table with 2-columns primary key