PostgresToEcto

PostgresToEcto turns explicitly selected PostgreSQL tables into readable Ecto schemas and one regenerable baseline migration.

Project status: 0.1.2 is the current renamed Wave 1 release. It provides the verified Wave 1 surface described below; deferred capabilities are not included.

Setup

Add PostgresToEcto to a development-only dependency in the consumer project:

defp deps do
  [{:postgres_to_ecto, "~> 0.1.2", runtime: false}]
end

Define one profile for the Repo and tables you want to generate:

defmodule MyApp.PostgresToEcto do
  use PostgresToEcto.Generator

  repo MyApp.Repo

  table "customers", module: MyApp.Customer
  table "sales.orders", module: MyApp.Order
end

Configure the default profile:

config :postgres_to_ecto, generator: MyApp.PostgresToEcto

Each selected table must name its Ecto module. Output paths are project-relative and must stay inside the Mix project. Unqualified table names use the Repo's :migration_default_prefix, or public when it is not configured.

Migrating from `pg_to_ecto`

The postgres_to_ecto 0.1.2 release is a breaking rename with no compatibility aliases. Commit your work, apply and review these mechanical replacements, then run a dry run:

Change the dependency from :pg_to_ecto to :postgres_to_ecto and use ~> 0.1.2.
Change the formatter import from :pg_to_ecto to :postgres_to_ecto.
Change the application configuration key from :pg_to_ecto to :postgres_to_ecto.
Change PgToEcto module references to PostgresToEcto.
Change mix pg_to_ecto.generate to mix postgres_to_ecto.generate.
Change generated use PgToEcto.Schema and use PgToEcto.Migration lines to their PostgresToEcto equivalents.
Change @pg_to_ecto_key to @postgres_to_ecto_key.
Change the managed-key prefix from pgte1: to postgreste1: and leave the encoded payload unchanged.
Change project-local paths containing pg_to_ecto to postgres_to_ecto.

Do not run --force merely to cross the rename boundary: force replacement can discard user-owned content in a file that still uses the old marker. Commit your work and review every mechanical replacement before running mix postgres_to_ecto.generate --dry-run.

Generate

From the consumer project:

mix deps.get
mix postgres_to_ecto.generate --dry-run
mix postgres_to_ecto.generate

The dry run introspects the source, renders every output, validates managed files, and prints planned create/update actions without writing. If every output already matches, it prints No changes required. Pass a profile explicitly when it is not configured as the default:

mix postgres_to_ecto.generate MyApp.PostgresToEcto --dry-run

Diagnostics are shown by default. Use --verbose for a safe context summary containing the profile, Repo, selected-table count, and migration path. Use --force only after reviewing the warning. Force can replace an unmanaged output file completely or reset PostgresToEcto-managed regions; user source outside those regions remains intact. Git is the recovery mechanism and PostgresToEcto does not create backups.

The task starts a configured Repo temporarily when it is not already running. PostgresToEcto reads PostgreSQL catalogs only. It does not read application rows, run source migrations, or write to the inspected database.

The programmatic operation is also available:

PostgresToEcto.generate(MyApp.PostgresToEcto, dry_run: true)

The result reports file actions and structured diagnostics. Warnings identify omitted or ambiguous mappings. Errors block output writes.

Generated ownership

Generated schema files and the baseline migration are mixed-ownership files. PostgresToEcto owns visible generated_settings, generated_fields, and generated_change regions plus one postgreste1: managed key. It updates only those regions and preserves virtual fields, associations, functions, changesets, and custom migration code around them.

A normal regeneration refuses missing, malformed, copied, or mismatched managed keys and unmanaged files. --force is the explicit recovery path. Repeated generation is idempotent and unchanged files are not rewritten.

Add the optional formatter import to a consumer's .formatter.exs:

[
  import_deps: [:ecto, :ecto_sql, :postgres_to_ecto]
]

Capability matrix

Capability	Status
Explicit table and module selection	Supported
Qualified and unqualified table names	Supported
`public` and selected non-public schemas	Supported
Ordinary tables and common string, integer, boolean, and identifier types	Supported
Nullability, safe literal defaults, primary keys, foreign keys, and referential actions	Supported for the verified Wave 1 surface
Ordinary and unique indexes	Supported
Foreign keys to unselected tables	Partial: local fields remain and a warning is emitted
Unmappable ordinary schema fields	Partial: migration identity is preserved and the schema field is omitted with a warning
Mixed user/generated source and safe regeneration	Supported
Dry run, force recovery, atomic per-file replacement, and no-op generation	Supported
Composite keys, UUIDs, decimals, arrays, advanced indexes, checks, and generated columns	Deferred to Wave 2
Enums, domains, extensions, views, triggers, grants, and PostgreSQL-native objects	Deferred
Historical or incremental migration reconstruction	Not part of the initial product
Automatic `many_to_many` inference and changeset generation	Deferred

The migration is a declarative local-development baseline. It is not a reconstruction of production migration history.

Demo consumer

The nested demo/ project uses synthetic, disposable PostgreSQL databases and checked-in source fixtures. It never uses company databases or application data.

cd demo
mix deps.get
mix demo.reset
mix postgres_to_ecto.generate --dry-run
mix postgres_to_ecto.generate
mix test

The demo uses POSTGRES_HOST, POSTGRES_PORT, POSTGRES_USER, POSTGRES_PASSWORD, and POSTGRES_DB. POSTGRES_PASSWORD is required and has no fallback. The default source database is postgres_to_ecto_demo_test; the target is its _target counterpart. Lifecycle commands refuse database names outside the postgres_to_ecto* family. No .env file is loaded automatically.

Development

mix deps.get
mix format --check-formatted
mix compile --warnings-as-errors
mix test

This documentation describes the verified Wave 1 behavior included in the 0.1.2 release; deferred capabilities are not included.