PhoenixKit.Migrations.UUIDFKColumns (phoenix_kit v2.2.0)

Adds UUID FK columns alongside integer FKs across PhoenixKit tables.

Called from V56 migration. This helper module keeps V56 manageable by extracting the UUID FK column creation logic (~80 columns across ~40 tables).

How It Works

For each FK column, three operations:

ALTER TABLE ... ADD COLUMN IF NOT EXISTS {uuid_fk} UUID
Backfill via JOIN: UPDATE t SET {uuid_fk} = s.uuid FROM source s WHERE s.id = t.{int_fk}
CREATE INDEX IF NOT EXISTS ... ON table({uuid_fk})

Large tables use batched backfills (PL/pgSQL DO block, 10k rows/batch) to avoid long-running transactions.

After columns are created and backfilled, add_constraints/1 adds:

NOT NULL constraints where the integer FK is NOT NULL
FK constraints where the integer FK has an explicit DB-level FK constraint

Safety

All operations wrapped in table_exists? + column_exists? checks
FK constraint creation uses pg_constraint existence check (idempotent)
NOT NULL uses ALTER COLUMN SET NOT NULL (idempotent in PostgreSQL)
Idempotent — safe to run multiple times

Summary

Functions

add_constraints(opts)

Adds NOT NULL constraints and FK constraints to UUID FK columns.

down(opts)

drop_constraints(opts)

Drops FK constraints and NOT NULL from UUID FK columns.

fk_constraint_name(table, uuid_fk)

The FK constraint name add_fk_constraint/7/drop_fk_constraint/4 use for {table, uuid_fk} — fk_<table minus the phoenix_kit_ prefix>_<uuid_fk>. Exposed so V163's repair names constraints identically to what this module itself would have created, instead of re-deriving the same string format a second time.

fk_constraints()

The {table, uuid_fk, ref_table, ref_col, on_delete} tuples add_constraints/1 builds FK constraints from — exposed for the same reason as not_null_uuid_fks/0: PhoenixKit.Migrations.Postgres.V163 drives its missing-FK repair off this exact list rather than a second copy of it. Not otherwise meant as a public contract.

not_null_uuid_fks()

The {table, uuid_fk_column} pairs add_constraints/1 sets NOT NULL on — exposed so PhoenixKit.Migrations.Postgres.V163 (a later repair for installs that ran the V56/V57 flush-order bug — see that migration's moduledoc) can drive the same list without duplicating it. Not otherwise meant as a public contract; if a future addition to @not_null_uuid_fks changes shape, this accessor and V163's consumption of it move together.

up(opts)

Functions

add_constraints(opts)

Adds NOT NULL constraints and FK constraints to UUID FK columns.

Must be called AFTER up/1 so that columns exist and are backfilled.

Order: NOT NULL first (data already backfilled), then ensure unique indexes on all FK-target tables, then FK constraints.