Working with Existing Databases

This page is for developers who already have a working database and want to bring it under Propulsion instead of starting a schema from scratch. Propulsion provides bin/propulsion schema:reverse, a command-line tool that connects to a live database and reverse-engineers its structure into the abstract XML schema format used to generate model classes.

Working with database structures

Propulsion uses an abstract XML schema file to represent databases (see the schema reference). It builds RDBMS-specific SQL from that schema — and can also reverse-engineer the schema file from an existing database’s metadata.

Creating an XML schema from a DB structure

schema:reverse connects to a live database over PDO and inspects its tables, columns, types, foreign keys, and indices to produce a schema.xml. This is useful when integrating with a legacy database, or when starting a new project from a schema someone else already built by hand.

To generate the schema:

Run schema:reverse with a PDO DSN, a name for the generated <database> element, and the source database adapter:

php bin/propulsion schema:reverse \
    --dsn="pgsql:host=localhost;dbname=mydb" \
    --database=pgsql \
    --database-name=mydb \
    --user=me \
    --password=secret

Review the console output for any errors or warnings, then inspect the generated schema file.
By default the schema is written to ./schema.xml in the current directory; use --output-file (-o) to change that. You can now proceed with model generation:
Terminal window
```
php bin/propulsion model:build schema.xml --output-dir=src/Model --database=pgsql
```

The reverse alias also works, for anyone used to typing the shorter Propel 1 command name:

php bin/propulsion reverse --dsn="mysql:host=localhost;dbname=mydb" --database=mysql --database-name=mydb -o schema.xml

Options

Option	Description	Default
`--dsn`	PDO DSN of the live database to reverse-engineer. Required.	—
`--database-name`	Name to use for the `<database name="...">` attribute in the generated schema. Required.	—
`--database`, `-d`	Source database adapter (`mysql`, `pgsql`, `sqlite`, …) — selects which `SchemaParser`/`Platform` to use.	resolved from config
`--user`, `-u` / `--password`, `-p`	Database credentials, if not embedded in the DSN.	—
`--output-file`, `-o`	Path to write the generated `schema.xml` to.	`./schema.xml`
`--add-validators`	Comma-separated list of validators to add to generated columns: `none`, `maxlength`, `maxvalue`, `type`, `required`, `unique`, `all`.	`none`
`--config`, `-c`	A `build.php`/`build.properties` file overriding `generator/default.php` (repeatable; later files win).	`[]`

schema:reverse has no built-in option to exclude tables from the generated schema. If your database includes tables you don’t want reflected in it (third-party tables, framework-internal tables, and so on), remove the corresponding <table> elements from the generated schema.xml by hand before using it to build models.

Limitations

schema:reverse does not reverse-engineer views, materialized views, or PostgreSQL enum types — these aren’t supported as first-class schema objects. If you want to use a view within Propulsion, define it manually as a <table> with skipSql="true" to generate read-only Object Model/Query classes against it without Propulsion trying to CREATE TABLE it.

The level of detail available also depends on the source database: metadata for SQLite is comparatively basic, since SQLite is a dynamically-typed database with limited column-type information to reverse-engineer from.

Migrating structure to a new RDBMS

Because Propulsion can both reverse-engineer an XML schema from an existing database and generate RDBMS-specific DDL from that schema, you can use it as a bridge to move a structure from one database engine to another:

Follow the steps above to produce a schema.xml from the existing database.
Change the target database adapter and connection settings in your project’s configuration to point at the new database.
Run sql:build to generate DDL for the new target:
Terminal window
```
php bin/propulsion sql:build
```
Run sql:exec to execute that DDL against the new database:
Terminal window
```
php bin/propulsion sql:exec
```