# `PgFlow.Migration`
[🔗](https://github.com/agoodway/pgflow/blob/v0.1.0/lib/pgflow/migration.ex#L1)

Installs the pgflow core schema (tables, triggers, functions) into a
consumer app's database via EctoEvolver.

## Usage (consumer side)

A consumer uses `mix pgflow.setup` to generate a wrapper migration:

    defmodule MyApp.Repo.Migrations.SetupPgflow do
      use Ecto.Migration

      def up do
        PgFlow.Migration.up()
        PgFlow.HelpersMigration.up()
      end

      def down do
        PgFlow.HelpersMigration.down()
        PgFlow.Migration.down()
      end
    end

## Prerequisites

This migration assumes the following are already in place in the target DB:

  * `pgmq` schema and its functions (install via `mix pgflow.gen.pgmq_migration`)
  * `pg_cron` extension registered (`CREATE EXTENSION pg_cron`)
  * Standard Postgres extensions: `citext`, `pg_trgm`, `pgcrypto`

Ordering: the prerequisites above must be applied first (separate
migrations). The typical project-level order is
`postgres_extensions → pgmq → pgflow.setup`, where `setup` bundles a
wrapper migration that runs `PgFlow.Migration.up/0` then
`PgFlow.HelpersMigration.up/0` in one transaction.

## Schema prefix

The SQL bundle hardcodes `"pgflow"` as the schema name (matching upstream
conventions). `default_prefix: "pgflow"` is fixed; runtime prefix override
via `up(prefix: ...)` is not supported by this version because it would
require rewriting every qualified reference in the vendored SQL. If the
library later needs multi-tenant schema prefixes, regenerate the bundle
with `$SCHEMA$` placeholders.

## Versioning

New upstream pgflow releases become `V02`, `V03`, ... — each a delta from
the previous version. V01 is never rewritten; existing deployments apply
only new versions on upgrade.

## Legacy install detection

`up/1` refuses to run V01 DDL against a schema that already contains
pgflow tables but is missing EctoEvolver's tracking comment — a restored
dump that lost comments, a manual `psql` seed, or any schema not installed
by `PgFlow.Migration.up/0` itself. The raised error points the operator at
`mix pgflow.stamp`, which adopts the existing schema into the tracking
model without re-running the bundle.

# `current_version`

# `down`

# `migrated_version`

# `up`

```elixir
@spec up(keyword()) :: :ok
```

Installs or upgrades the pgflow schema to the latest version.

Options:

  * `:prefix` — schema prefix (default `"pgflow"`).
  * `:version` — target version (default: latest).

Raises if the target schema already contains pgflow tables without an
EctoEvolver tracking comment — see "Legacy install detection" above.

---

*Consult [api-reference.md](api-reference.md) for complete listing*