Code Overview - pgAdmin 4 4.20 documentation

Runtime ¶

The runtime is essentially a Python webserver and browser in a box. Found in the /runtime directory in the source tree, it is a relatively simple QT application that is most easily modified using the QT Creator application.

Web Application ¶

The web application forms the bulk of pgAdmin and can be found in the /web directory in the source tree. The main file is pgAdmin4.py which can be used to run the built-in standalone web server, or as a WSGI application for production use.

pgAdmin Core ¶

The heart of pgAdmin is the pgadmin package. This contains the globally available HTML templates used by the Jinja engine, as well as any global static files such as images, Javascript and CSS files that are used in multiple modules.

The work of the package is handled in it’s constructor, __init__.py . This is responsible for setting up logging and authentication, dynamically loading other modules, and a few other tasks.

Modules ¶

Units of functionality are added to pgAdmin through the addition of modules. Theses are Python object instance of classes, inherits the PgAdminModule class (a Flask Blueprint implementation), found in web/pgadmin/utils.py . It provide various hook points for other modules to utilise (primarily the default module - the browser).

To be recognised as a module, a Python package must be created. This must:

1. Be placed within the web/pgadmin/ directory, and
2. Implements pgadmin.utils.PgAdminModule class
3. An instance variable (generally - named blueprint ) representing that particular class in that package.

Each module may define a template and static directory for the Blueprint that it implements. To avoid name collisions, templates should be stored under a directory within the specified template directory, named after the module itself. For example, the browser module stores it’s templates in web/pgadmin/browser/templates/browser/ . This does not apply to static files which may omit the second module name.

In addition to defining the Blueprint, the views module is typically responsible for defining all the views that will be rendered in response to client requests, we must provide a REST API url(s) for these views. These must include appropriate route and security decorators. Take a look at the NodeView class, which uses the same approach as Flask’s MethodView, it can be found in web/pgadmin/browser/utils.py . This specific class is used by browser nodes for creating REST API url(s) for different operation on them. i.e. list, create, update, delete, fetch children, get statistics/reversed SQL/dependencies/dependents list for that node, etc. We can use the same class for other purpose too. You just need to inherit that class, and overload the member variables operations, parent_ids, ids, node_type, and then register it as node view with PgAdminModule instance.

Most pgAdmin modules will also implement the hooks provided by the PgAdminModule class. This is responsible for providing hook points to integrate the module into the rest of the application - for example, a hook might tell the caller what CSS files need to be included on the rendered page, or what menu options to include and what they should do. Hook points need not exist if they are not required. It is the responsiblity of the caller to ensure they are present before attempting to utilise them.

Hooks currently implemented are:

class MyModule(PgAdminModule):
    """
    This is class implements the pgadmin.utils.PgAdminModule, and
    implements the hooks
    """

    ...

    def get_own_stylesheets(self):
        """
        Returns:
            list: the stylesheets used by this module, not including any
                  stylesheet needed by the submodules.
        """
        return [url_for('static', 'css/mymodule.css')]

    def get_own_javascripts(self):
        """
        Returns:
            list of dict:
            - contains the name (representation for this javascript
              module), path (url for it without .js suffix), deps (array of
              dependents), exports window object by the javascript module,
              and when (would you like to load this javascript), etc
              information for this module, not including any script needed
              by submodules.
        """
        return [
            {
                'name': 'pgadmin.extension.mymodule',
                'path': url_for('static', filename='js/mymodule'),
                'exports': None,
                'when': 'server'
                }
            ]

    def get_own_menuitems(self):
        """
        Returns:
            dict: the menuitems for this module, not including
                  any needed from the submodules.
        """
        return {
            'help_items': [
                MenuItem(
                    name='mnu_mymodule_help',
                    priority=999,
                    # We need to create javascript, which registers itself
                    # as module
                    module="pgAdmin.MyModule",
                    callback='about_show',
                    icon='fa fa-info-circle',
                    label=gettext('About MyModule'
                    )
                ]
            }
    def get_panels(self):
        """
        Returns:
            list: a list of panel objects to add implemented in javascript
                  module
        """
        return []
    ...



blueprint = MyModule('mymodule', __name__, static_url_path='/static')

pgAdmin Modules may include any additional Python modules that are required to fulfill their purpose, as required. They may also reference other dynamically loaded modules, but must use the defined hook points and fail gracefully in the event that a particular module is not present.

Nodes ¶

Nodes are very similar to modules, it represents an individual node or, collection object on the browser treeview. To recognised as a node module, a Python package (along with javascript modules) must be created. This must:

1. Be placed within the web/pgadmin/browser/ directory, and
2. Implements the BrowserPluginModule, and registers the node view, which exposes required the REST APIs
3. An instance of the class object

Front End ¶

pgAdmin uses javascript extensively for the front-end implementation. It uses require.js to allow the lazy loading (or, say load only when required), bootstrap for UI look and feel, Backbone for data manipulation of a node, Backform for generating properties/create dialog for selected node. We have divided each module in small chunks as much as possible. Not all javascript modules are required to be loaded (i.e. loading a javascript module for database will make sense only when a server node is loaded competely.) Please look at the the javascript files node.js, browser.js, menu.js, panel.js, etc for better understanding of the code.