chore(core): Change db column type to TEXT for subject_id

[afitzek]

Summary

This PR addresses a database limitation where the subject_id column in the dynamic_credential_entry table was restricted to varchar(16), which is insufficient for certain dynamic credential resolvers that generate longer subject identifiers.

Changes Made

• Migration: Created ExpandSubjectIDColumnLength1769690595000 migration that:
• Changes subject_id column type from varchar(16) to TEXT (unbounded)
• Recreates the table for both PostgreSQL and SQLite (required because subject_id is part of the composite primary key)
• Preserves all existing data using the copyTable utility (batch copying in chunks of 10 rows)
• Maintains all constraints (primary key, foreign keys, indexes)
• Postgres does not support the short syntax for LIMIT and OFFSET (this was changed in the copyTable migration helper)

Why Table Recreation?

The subject_id column is part of a composite primary key (credential_id, subject_id, resolver_id). Both PostgreSQL and SQLite have restrictions on altering columns that are part of primary key constraints:

• PostgreSQL: Cannot alter column type when it's part of a primary key without dropping the constraint first
• SQLite: Cannot drop columns that are part of a primary key

The cleanest and safest approach is to recreate the table with the new schema, which the migration does using n8n's built-in copyTable utility that handles data preservation, foreign keys, and indexes.

Related Linear tickets, Github issues, and Community forum posts

closes https://linear.app/n8n/issue/IAM-204/increase-varchar-limit-for-subjectid-column-in-postgrest-for-dynamic

Review / Merge checklist

• PR title and summary are descriptive. (conventions)
• Docs updated or follow-up ticket created.
• Tests included.
• PR Labeled with release/backport (if the PR is an urgent fix that needs to be backported)

[codecov]

Codecov Report

❌ Patch coverage is 38.46154% with 8 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ommon/1769690595000-ExpandSubjectIDColumnLength.ts	30.00%	7 Missing ⚠️
...ckages/@n8n/db/src/migrations/migration-helpers.ts	0.00%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

[cubic-dev-ai]

No issues found across 5 files

[tomi]

I am a little concerned about having an unconstrainted column that is part of a PK. Does it make sense to be in the PK? Could we apply at least some limit to it?

[afitzek]

I am a little concerned about having an unconstrainted column that is part of a PK. Does it make sense to be in the PK? Could we apply at least some limit to it?

@tomi Ah yes, this is a good point thanks. I'll change the type to some long VARCHAR. I'll do some research on what limit makes sense here.