Remap failure when changing discourse domain

Installation
1

Hi,
I tried to change a discourse domain name, following Change the domain name or rename your Discourse. Things looked right until I launched the command

discourse remap talk.foo.com talk.bar.com

I got the following:

root@plop:/var/www/discourse# discourse remap plop.domain.fr forum.plop.fr
Rewriting all occurrences of plop.domain.fr to forum.plop.fr
THIS TASK WILL REWRITE DATA, ARE YOU SURE (type YES)
YES
backup_metadata=1
email_logs=991
javascript_caches=1
post_revisions=126
post_search_data=20
posts=782
stylesheet_cache=446
theme_settings=1
Error: ERROR:  duplicate key value violates unique constraint "unique_post_links"
DETAIL:  Key (topic_id, post_id, url)=(274, 455, http://forum.plop.fr) already exists.
The remap has only been partially applied due to the error above. Please re-run the script again.

It seemed it looked like to the error reported here, but was slightly different. I guess the bug is related to the fact that the new domain has been discussed on the forum.

To overcome it, I was unable to launch something like db:exec to force db commands via rake. So I did it directly via postgres:

  1. connect the dababase:
# cd /var/discourse/
# ./launcher enter app
# su - postgres
$ psql
postgres=# \c discourse
  1. try to directly replace url in the table
discourse=# update topic_links set url=REPLACE(url, 'plop.domain.fr', 'forum.plop.fr');
ERROR:  duplicate key value violates unique constraint "unique_post_links"
DETAIL:  Key (topic_id, post_id, url)=(274, 455, http://forum.plop.fr) already exists.
  1. on error : force a replacement that don’t break unicity, e.g. forum.plop.fr/:
discourse=# update topic_links set url=REPLACE(url, 'plop.domain.fr', 'forum.plop.fr/') where topic_id=274;
  1. repeat 3. until 2. finishes without error. Then quit pg.
discourse=# update topic_links set url=REPLACE(url, 'plop.domain.fr', 'forum.plop.fr');
UPDATE 1349
discourse=# 
\q
  1. relaunch the remap and the rebake:
$ exit
# discourse remap plop.domain.fr forum.plop.fr
  1. Manually check and correct the problematic topics (which content may be inconsistent), by visiting forum.plop.fr/t/topic/274 and others.
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2

If I correctly understand the problem a posteriori, the doc could suggest to remove all old occurrences of talk.bar.com prior to launch this command. It could simply done via

discourse remap talk.bar.com talk.foo-or-bar-that-s-the-question.com

(I didn’t tried.)

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