Re: Merging records in a table with 2-columns primary key

Hello Andy and others -

On Sun, Apr 2, 2017 at 5:13 PM, Andy Colson <andy(at)squeakycode(dot)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