duplicate key value violates unique constraint "subscribers_email_key"

[allentown521]

1. List 1 successfully imports the email.csv file first
2. Import the email-1.csv file from List 1 (some email addresses exist in email.csv), Overwrite user info = true

What I hoped for was normal import, just updating the user information for existing email addresses. Everything worked fine in version 4, but yesterday after upgrading to version 6.2, I couldn't import:

2026/07/18 03:35:00.638423 error executing insert: pq: duplicate key value violates unique constraint "subscribers_email_key"
2026/07/18 03:35:00.638559 error committing to DB: sql: transaction has already been committed or rolled back

Has the import logic changed? If user information with the same email address cannot be updated, what is the significance of the Overwrite user info option?

[knadh]

The logic hasn't changed but I think this may likely be because your subscribers table has somehow ended up with non-lowercase e-mails. While listmonk always forcibly lowercased e-mails from the earliest version, an index to prevent duplicates in the table was added later (but never added to any migrations because that would break on instances where somehow non-lowercased duplicates had ended up).

Could you please try this?

a) Run this query to see any existing duplicate e-mails. If there are any, please delete the duplicates from the UI. This is a read-only query and doesn't make any changes.

 --- Show any existing duplicates
 SELECT lower(btrim(email)) AS std_email, count(*) AS n, array_agg(id ORDER BY id) AS ids
 FROM subscribers GROUP BY lower(btrim(email)) count(*) > 1 BY n DESC;

b) Lowercase existing e-mails that aren't already, and add the missing index. This makes changes to the records, so please take a backup first.

BEGIN;
 --- Lowercase all existing email IDs in the table.
 UPDATE subscribers SET email = lower(btrim(email))  WHERE email <> lower(btrim(email));

--- Create the missing index.
 CREATE UNIQUE INDEX IF NOT EXISTS idx_subs_email ON subscribers (lower(email));
COMMIT;