Feat!: Add support for virtual statements to be executed post update

[themisvaltinos]

This update introduces statements that are executed after a virtual update. These can be used for example to grant privileges on views of the virtual layer.

These expressions should be defined within a ON_VIRTUAL_UPDATE_BEGIN; ...; ON_VIRTUAL_UPDATE_END; block. For example:

MODEL (
  name db.customers 
);

SELECT 
  item_id
FROM 
  db.seed_model;

ON_VIRTUAL_UPDATE_BEGIN; 

GRANT SELECT ON VIEW @this_model TO ROLE role_name;

INJA_STATEMENT_BEGIN;     
GRANT REFERENCES, SELECT ON FUTURE VIEWS IN DATABASE {{ db }} TO ROLE owner_name;  
JINJA_END;  

ON_VIRTUAL_UPDATE_END;

Jinja expressions are also supported within this block by properly nesting the Jinja block as shown in the example above.

In these statements table resolution occurs at the virtual level, meaning that qualified view names (including @this_model) are used instead of the physical table names. For example, when running the plan in an environment named dev, the db.customers as well as this_model would resolve to db__dev.customers rather than the physical table.

For python models these statements are defined in the @model decorator:

@model( 
  "db.customers",  
  on_virtual_update=["GRANT SELECT ON VIEW @this_model TO ROLE role_name;"]
)

[izeigerman]

Can we please make sure this feature is documented before we merge.

[izeigerman]

Do we still need to pass deployability_index here?

[themisvaltinos]

oh right we don't will remove this

[izeigerman]

[Nit] I guess we can return empty dict here if the environment is prod

[themisvaltinos]

I tried it, but it didn't work since it led to the model names been mapped to the physical table names. This is because in resolve tables without this dict or an empty dict: _to_table_mapping is used to create the mapping:

sqlmesh/sqlmesh/core/renderer.py

Line 281 in c8fc94e

**self._to_table_mapping(snapshots.values(), deployability_index),

[izeigerman]

This looks great, thank you!