# Known Issues

The following summarizes notable known issues, in particular those
that affect sharing YAML specifications with the Pyrseas utilitites.

## Coverage of Database Objects

Perseid currently supports a subset of PostgreSQL objects focused on
schemas, tables, columns, and their constraints. Future releases are
planned to support the other objects covered by Pyrseas.  For details
on what is currently supported, see the [API
Reference](../api/index.md).

### PostgreSQL Extensions

Perseid does not currently extract or recognize PostgreSQL
extensions. As a result:

- `dbtoyaml` does not emit `extension` entries, even if the database
  has extensions installed (e.g. `plpgsql`).
- `yamltodb` will reject a YAML specification that contains
  `extension` objects (e.g. Pyrseas-generated output) with an
  `Unrecognized object type` error.
- Applying Perseid-generated YAML against a database that has
  extensions may cause Pyrseas tools to emit `DROP EXTENSION`
  statements when comparing against a specification that omits them.

Support for PostgreSQL extensions will be added in a future release.

## YAML Formatting

Perseid's YAML output differs cosmetically from Pyrseas in a few
respects:

- **Key ordering**: Perseid preserves insertion order when emitting
  YAML mappings, while Pyrseas sorts keys alphabetically.
- **Spacing/indentation**: There are minor differences in sequence
  indentation and line formatting.

These differences do not affect the parsing of the YAML structures.

## Statement Ordering

When generating SQL with `yamltodb`, the order of `DROP` statements
for tables and constraints may differ from Pyrseas. Both produce valid
SQL for the same set of objects; the differences only appear when
there are no dependency constraints that force a specific order.