Merge pull request #723 from vitessio/hg-dbddl-plugin

create and drop database plugin documentation

content/en/docs/reference/compatibility/mysql-compatibility.md

@@ -149,3 +149,23 @@ USE `mykeyspace:-80@rdonly`
 ```
 
 A similar effect can be achieved by using a database name like `mykeyspace:-80@rdonly` in your MySQL application client connection string.
+
+### Create/Drop Database
+
+Vitess does not support CREATE and DROP DATABASE queries out of the box.
+
+But, to make it possible to provision databases, a plugin mechanism exists. 
+The plugin has to take care of creating and dropping the database, and update the topology & VSchema so that Vitess can start receiving queries for the new keyspace.
+
+The plugin should implement the `DBDDLPlugin` interface, and be saved into a new file in the `go/vt/vtgate/engine/` directory.
+
+```go
+type DBDDLPlugin interface {
+	CreateDatabase(ctx context.Context, name string) error
+	DropDatabase(ctx context.Context, name string) error
+}
+```
+
+It must then register itself calling `DBDDLRegister`. 
+You can take a look at the `dbddl_plugin.go` in the engine package for an example of how it's done.
+Finally, you need to add a command line flag to vtgate to have it use the new plugin: `-dbddl_plugin=myPluginName`