fix(tasks): temporary tool to detect and merge codebar auth duplicate members

[mroderick]

Problem

When the codebar auth flow was merged on 2026-08-06, members with an existing GitHub account whose email differed from their stored email could not be matched automatically. The codebar auth flow created new member accounts instead of linking to existing ones (#2805).

Solution

Add a temporary rake task and Makefile targets to detect and safely merge duplicate members.

Detection strategies

• name+surname — exact case-insensitive match
• email — exact case-insensitive match
• first-name+uid-surname — first name matches; duplicate has no surname, but the codebar auth UID contains the original's surname
• domain+local-part — non-generic domain with overlapping local parts

Plus hard-coded manual overrides for edge cases the heuristics cannot detect.

Safety

• Dry run by default — must pass APPLY=1 to change data.
• Idempotent — re-running after a merge reports no duplicates.
• Deactivates, not deletes — duplicate emails are renamed to duplicate.<id>.merged-into.<id>@codebar.io, auth services and roles are removed, and a MemberNote preserves audit history.
• Logged — every real run writes to a new timestamped JSON log at log/merge_duplicate_members/run_YYYYMMDDTHHMMSSZ.json.

Usage

make detect_duplicate_members   # list duplicates
make fix_duplicate_members      # dry run
make fix_duplicate_members APPLY=1  # execute
make verify_duplicate_members   # confirm none remain

Production:

heroku run rake member:duplicates:fix APPLY=1 --app codebar-production

Files

• lib/tasks/merge_duplicate_members.rake — detection and merge logic
• Makefile — convenience targets for local and Heroku operation
• docs/merge_duplicate_members.md — operator documentation

Testing

• Run against a fresh production dump (make dump_production).
• Dry run shows all actions without modifying data.
• Verify task exits 0 when no duplicates remain.

---

This is a temporary tool. Once the existing duplicates are resolved, it can be removed.

[mroderick]

Applied to production. 12 duplicate members merged successfully. All verified clean afterwards — no duplicates remain.

Log:

{
  "timestamp": "2026-08-21T10:44:25+02:00",
  "dry_run": false,
  "environment": "development",
  "merges": [
    { "dup_id": 31262, "orig_id": 553, "strategies": "name+surname", "status": "success" },
    { "dup_id": 31263, "orig_id": 655, "strategies": "first-name+uid-surname", "status": "success" },
    { "dup_id": 31230, "orig_id": 5583, "strategies": "name+surname", "status": "success" },
    { "dup_id": 31224, "orig_id": 17284, "strategies": "name+surname", "status": "success" },
    { "dup_id": 31243, "orig_id": 22921, "strategies": "name+surname", "status": "success" },
    { "dup_id": 31233, "orig_id": 24686, "strategies": "name+surname", "status": "success" },
    { "dup_id": 31232, "orig_id": 25640, "strategies": "name+surname", "status": "success" },
    { "dup_id": 31258, "orig_id": 27714, "strategies": "domain+local-part", "status": "success" },
    { "dup_id": 31257, "orig_id": 27714, "strategies": "manual", "status": "success" },
    { "dup_id": 31261, "orig_id": 29893, "strategies": "email", "status": "success" },
    { "dup_id": 31229, "orig_id": 30581, "strategies": "name+surname", "status": "success" },
    { "dup_id": 31218, "orig_id": 31192, "strategies": "email", "status": "success" }
  ],
  "errors": [],
  "total_merges": 12
}

[mroderick]

Applied to production again tonight:

{
  "timestamp": "2026-08-31T23:56:30+02:00",
  "dry_run": false,
  "environment": "development",
  "merges": [
    {
      "dup_id": 31284,
      "orig_id": 21098,
      "strategies": "name+surname",
      "status": "success"
    },
    {
      "dup_id": 31295,
      "orig_id": 31133,
      "strategies": "name+surname",
      "status": "success"
    }
  ],
  "errors": [],
  "total_merges": 2
}

[mroderick]

{
  "timestamp": "2026-09-09T11:49:49+02:00",
  "dry_run": false,
  "environment": "development",
  "merges": [
    {
      "dup_id": 31292,
      "orig_id": 13771,
      "strategies": "manual",
      "status": "success"
    }
  ],
  "errors": [],
  "total_merges": 1
}

[mroderick]

Applied to production today (2026-10-08), run from a local DB_URL with the task file at this PR's head (142d292). Production backup captured first (heroku pg:backups:capture → b032). Working tree untouched; the run log is reproduced below.

{
  "timestamp": "2026-10-08T15:35:30+02:00",
  "dry_run": false,
  "environment": "development",
  "merges": [
    { "dup_id": 31476, "orig_id": 6573,  "strategies": "manual", "status": "success" },
    { "dup_id": 31440, "orig_id": 17359, "strategies": "manual", "status": "success" },
    { "dup_id": 31390, "orig_id": 18002, "strategies": "manual", "status": "success" },
    { "dup_id": 31419, "orig_id": 30879, "strategies": "manual", "status": "success" }
  ],
  "errors": [],
  "total_merges": 4
}

All four pairs were reviewed by hand before running; the merged members carry the duplicate.<id>.merged-into.<id>@codebar.io rename and audit MemberNotes, auth services moved to the originals, zero auth services left on the duplicates. Cumulative merges via this tool: 19.

One manual companion fix followed the merge for original 6573: the duplicate's auth uid was a sub-keyed value, and the auth-app user now carries a corrected mail address, so after moving services the original got a codebar auth_service with the corrected-address uid and the dormant sub-keyed row was deleted. Without it, the next sign-in for that person would create a third member.

Remaining low-confidence matches, left unmerged and still listed by member:duplicates:verify (PASS: no high-confidence duplicates remain):

• 31436 → 24631 (name+surname)
• 31336 → 25796 (name+surname) — documented false positive, cited in the task source
• 31343 → 28148 (first-name+uid-surname) — degenerate case: original's surname field is empty, so the uid-surname predicate matches anything; reduces to first-name-only
• 31421 → 30330 (name+surname)

Three notes for this PR before it merges (verified against current master):

1. member_email_deliveries now has a UNIQUE (member_id, email_type) index — the blind update_all(member_id:) in merge_member_email_deliveries can raise mid-run on a type collision between both members. Worth a per-row conflict check (today's pairs had none, so the run passed).
2. subscriptions gained discarded_at + a partial unique index — orig.subscriptions.exists?(group_id:) should filter to kept rows, else a discarded original subscription can cause a duplicate's active subscription to be destroyed instead of moved.
3. merge_invitations dedupes by event_id only; with the (member_id, event_id, role) unique index a role-aware check would move rows it currently destroys.

Also worth adding to this branch: the .gitignore line for /log/merge_duplicate_members/ is present here but absent on master — today's run left the log in the repo working tree.