Update failed - PG::UniqueViolation: ERROR

Hi guys,

I tried to update Discourse forum to the latest version 2.2.0.beta5 on stage instance, but it failed.

The error is:

I, INFO -- : > cd /var/www/discourse && su discourse -c 'bundle exec rake db:migrate'
rake aborted!
StandardError: An error has occurred, this and all later migrations canceled:
PG::UniqueViolation: ERROR:  duplicate key value violates unique constraint "index_polls_on_post_id_and_name"
DETAIL:  Key (post_id, name)=(662593, poll) already exists.

I logged into postgresql database and checked that there are no values in polls table, so it is strange why do we receive an error -  "Key (post_id, name)=(662593, poll) already exists.":
=> SELECT * FROM polls;
id | post_id | name | close_at | type | status | results | visibility | min | max | step | anonymous_voters | created_at | updated_at
(0 rows)

=> \d polls_id_seq
        Sequence "public.polls_id_seq"
    Column     |  Type   |        Value
 sequence_name | name    | polls_id_seq
 last_value    | bigint  | 4524
 start_value   | bigint  | 1
 increment_by  | bigint  | 1
 max_value     | bigint  | 9223372036854775807
 min_value     | bigint  | 1
 cache_value   | bigint  | 1
 log_cnt       | bigint  | 24
 is_cycled     | boolean | f
 is_called     | boolean | t
Owned by: public.polls.id

=> select count(id),max(id) from polls;
 count | max
     0 |
(1 row)

Can you, please, help with this issue.
As because of this error we cannot update Discourse forum.


Can someone from development team take a look to this question ?
We are blocked with update of Discourse forum to the latest version, because of this error.
And also we cannot install additional plugin, as docker container is not compiled and as a result is not running.

The error indicates that the post (id: 662593) has more than one polls named “poll”.

Can you share the raw of that post? You can find it by going to https://your.discourse/posts/662593/raw

Also, can you share the results of this command when ran in the rails console?

PostCustomField.where(post_id: 662593, name: "polls")

Unfortunately, I cannot share the raw of post from https://your.discourse/posts/662593/raw , as it is not running now because of error.

The output from rail`s console:

[1] pry(main)> PostCustomField.where(post_id: 662593, name: "polls")
=> [#<PostCustomField:0x00005641ffca5f48
  id: 376790,
  post_id: 662593,
  name: "polls",
  created_at: Thu, 26 Apr 2018 01:56:00 UTC +00:00,
  updated_at: Thu, 26 Apr 2018 01:56:00 UTC +00:00>]

:thinking: the data looks fine.

Can you try to clean all the polls related tables and then try to run the migration again?

There are 3 poll related tables.
I tried to delete rows, but these tables are empty.

=> DELETE FROM poll_options;
=> DELETE FROM poll_votes;
=> DELETE FROM polls;

Then ran the migration again, but it failed with the same error as earlier.

It turns out that the problem was that the poll had been duplicated in a quote block, and the migration didn’t know to ignore it. It was in a PM, apparently as an example of how polls worked. I deleted the duplicate and the migration ran fine.


Weird, I’ll have to test that…