# Table: `host_aliases`

Stores aliases for canonical hosts. Aliases are retained after retirement for audit and collision prevention.

## Columns

| Column | Type | Null | Default | Notes |
|--------|------|------|---------|-------|
| `alias_name` | `TEXT` | no | none | Alias DNS name or short alias. |
| `host_fqdn` | `TEXT` | no | none | Target host. References `hosts(fqdn)`. |
| `alias_kind` | `TEXT` | no | `'declared'` | `declared`, `derived`, or `derived-vhost`. |
| `status` | `TEXT` | no | `'active'` | Alias lifecycle state. |
| `is_dns_published` | `INTEGER` | no | `1` | Whether this alias should appear in generated DNS exports. |
| `created_at` | `TEXT` | no | none | ISO UTC creation timestamp. |
| `retired_at` | `TEXT` | yes | `NULL` | ISO UTC retirement timestamp. |
| `notes` | `TEXT` | no | `''` | Operator notes. |

## Keys And Indexes

- Primary key: `(alias_name, host_fqdn)`
- Unique partial index: `idx_host_aliases_active_name` on `alias_name` where `status = 'active'`
- Lookup index: `idx_host_aliases_host_status` on `(host_fqdn, status)`

## Relationships

- `host_fqdn` references `hosts(fqdn)` with `ON UPDATE CASCADE ON DELETE RESTRICT`

## Rules

- A retired alias is not deleted; `status` changes to `retired` and `is_dns_published` is set to `0`.
- One active alias can point to only one host.
- Derived short names such as `baobab` are persisted with `alias_kind = 'derived'`.
- Derived vhost short names such as `pmx.baobab` are persisted with `alias_kind = 'derived-vhost'`.

## Definition

```sql
CREATE TABLE IF NOT EXISTS host_aliases (
    alias_name TEXT NOT NULL,
    host_fqdn TEXT NOT NULL,
    alias_kind TEXT NOT NULL DEFAULT 'declared',
    status TEXT NOT NULL DEFAULT 'active',
    is_dns_published INTEGER NOT NULL DEFAULT 1,
    created_at TEXT NOT NULL,
    retired_at TEXT,
    notes TEXT NOT NULL DEFAULT '',
    PRIMARY KEY (alias_name, host_fqdn),
    FOREIGN KEY (host_fqdn) REFERENCES hosts(fqdn) ON UPDATE CASCADE ON DELETE RESTRICT
);

CREATE UNIQUE INDEX IF NOT EXISTS idx_host_aliases_active_name
ON host_aliases(alias_name)
WHERE status = 'active';

CREATE INDEX IF NOT EXISTS idx_host_aliases_host_status
ON host_aliases(host_fqdn, status);
```