Code Snippets

This document contains code for some of the important classes, listed as below:

PgAdminModule

PgAdminModule is inherted from Flask.Blueprint module. This module defines a set of methods, properties and attributes, that every module should implement.

class PgAdminModule(Blueprint):
    """
    Base class for every PgAdmin Module.

    This class defines a set of method and attributes that
    every module should implement.
    """

    def __init__(self, name, import_name, **kwargs):
        kwargs.setdefault('url_prefix', '/' + name)
        kwargs.setdefault('template_folder', 'templates')
        kwargs.setdefault('static_folder', 'static')
        self.submodules = []
        self.parentmodules = []

        super(PgAdminModule, self).__init__(name, import_name, **kwargs)

        def create_module_preference():
            # Create preference for each module by default
            if hasattr(self, 'LABEL'):
                self.preference = Preferences(self.name, self.LABEL)
            else:
                self.preference = Preferences(self.name, None)

            self.register_preferences()

        # Create and register the module preference object and preferences for
        # it just before the first request
        self.before_app_first_request(create_module_preference)

    def register_preferences(self):
        pass

    def register(self, app, options, first_registration=False):
        """
        Override the default register function to automagically register
        sub-modules at once.
        """
        if first_registration:
            self.submodules = list(app.find_submodules(self.import_name))

        super(PgAdminModule, self).register(app, options, first_registration)

        for module in self.submodules:
            if first_registration:
                module.parentmodules.append(self)
            app.register_blueprint(module)

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

    def get_own_messages(self):
        """
        Returns:
            dict: the i18n messages used by this module, not including any
                messages needed by the submodules.
        """
        return dict()

    def get_own_javascripts(self):
        """
        Returns:
            list: the javascripts used by this module, not including
                any script needed by the submodules.
        """
        return []

    def get_own_menuitems(self):
        """
        Returns:
            dict: the menuitems for this module, not including
                any needed from the submodules.
        """
        return defaultdict(list)

    def get_panels(self):
        """
        Returns:
            list: a list of panel objects to add
        """
        return []

    def get_exposed_url_endpoints(self):
        """
        Returns:
            list: a list of url endpoints exposed to the client.
        """
        return []

    @property
    def stylesheets(self):
        stylesheets = self.get_own_stylesheets()
        for module in self.submodules:
            stylesheets.extend(module.stylesheets)
        return stylesheets

    @property
    def messages(self):
        res = self.get_own_messages()

        for module in self.submodules:
            res.update(module.messages)
        return res

    @property
    def javascripts(self):
        javascripts = self.get_own_javascripts()
        for module in self.submodules:
            javascripts.extend(module.javascripts)
        return javascripts

    @property
    def menu_items(self):
        menu_items = self.get_own_menuitems()
        for module in self.submodules:
            for key, value in module.menu_items.items():
                menu_items[key].extend(value)
        menu_items = dict((key, sorted(value, key=attrgetter('priority')))
                          for key, value in menu_items.items())
        return menu_items

    @property
    def exposed_endpoints(self):
        res = self.get_exposed_url_endpoints()

        for module in self.submodules:
            res += module.exposed_endpoints

        return res

NodeView

NodeView class helps exposing basic REST APIs for different operations used by pgAdmin Browser. The basic idea has been taken from the Flask’s MethodView class. Because - we need a lot more operations (not, just CRUD), we can not use it directly.

class NodeView(with_metaclass(MethodViewType, View)):
    """
    A PostgreSQL Object has so many operaions/functions apart from CRUD
    (Create, Read, Update, Delete):
    i.e.
    - Reversed Engineered SQL
    - Modified Query for parameter while editing object attributes
      i.e. ALTER TABLE ...
    - Statistics of the objects
    - List of dependents
    - List of dependencies
    - Listing of the children object types for the certain node
      It will used by the browser tree to get the children nodes

    This class can be inherited to achieve the diffrent routes for each of the
    object types/collections.

       OPERATION   |             URL             | HTTP Method |    Method
    ---------------+-----------------------------+-------------+--------------
    List           | /obj/[Parent URL]/          | GET         | list
    Properties     | /obj/[Parent URL]/id        | GET         | properties
    Create         | /obj/[Parent URL]/          | POST        | create
    Delete         | /obj/[Parent URL]/id        | DELETE      | delete
    Update         | /obj/[Parent URL]/id        | PUT         | update

    SQL (Reversed  | /sql/[Parent URL]/id        | GET         | sql
    Engineering)   |
    SQL (Modified  | /msql/[Parent URL]/id       | GET         | modified_sql
    Properties)    |

    Statistics     | /stats/[Parent URL]/id      | GET         | statistics
    Dependencies   | /dependency/[Parent URL]/id | GET         | dependencies
    Dependents     | /dependent/[Parent URL]/id  | GET         | dependents

    Nodes          | /nodes/[Parent URL]/        | GET         | nodes
    Current Node   | /nodes/[Parent URL]/id      | GET         | node

    Children       | /children/[Parent URL]/id   | GET         | children

    NOTE:
    Parent URL can be seen as the path to identify the particular node.

    i.e.
    In order to identify the TABLE object, we need server -> database -> schema
    information.
    """
    operations = dict({
        'obj': [
            {'get': 'properties', 'delete': 'delete', 'put': 'update'},
            {'get': 'list', 'post': 'create'}
        ],
        'nodes': [{'get': 'node'}, {'get': 'nodes'}],
        'sql': [{'get': 'sql'}],
        'msql': [{'get': 'modified_sql'}],
        'stats': [{'get': 'statistics'}],
        'dependency': [{'get': 'dependencies'}],
        'dependent': [{'get': 'dependents'}],
        'children': [{'get': 'children'}]
    })

    @classmethod
    def generate_ops(cls):
        cmds = []
        for op in cls.operations:
            idx = 0
            for ops in cls.operations[op]:
                meths = []
                for meth in ops:
                    meths.append(meth.upper())
                if len(meths) > 0:
                    cmds.append({
                        'cmd': op, 'req': (idx == 0),
                        'with_id': (idx != 2), 'methods': meths
                    })
                idx += 1
        return cmds

    # Inherited class needs to modify these parameters
    node_type = None
    # This must be an array object with attributes (type and id)
    parent_ids = []
    # This must be an array object with attributes (type and id)
    ids = []

    @classmethod
    def get_node_urls(cls):
        assert cls.node_type is not None, \
            "Please set the node_type for this class ({0})".format(
                str(cls.__class__.__name__))
        common_url = '/'
        for p in cls.parent_ids:
            common_url += '<{0}:{1}>/'.format(str(p['type']), str(p['id']))

        id_url = None
        for p in cls.ids:
            id_url = '{0}<{1}:{2}>'.format(common_url if not id_url else id_url,
                                           p['type'], p['id'])

        return id_url, common_url

    def __init__(self, **kwargs):
        self.cmd = kwargs['cmd']

    # Check the existance of all the required arguments from parent_ids
    # and return combination of has parent arguments, and has id arguments
    def check_args(self, **kwargs):
        has_id = has_args = True
        for p in self.parent_ids:
            if p['id'] not in kwargs:
                has_args = False
                break

        for p in self.ids:
            if p['id'] not in kwargs:
                has_id = False
                break

        return has_args, has_id and has_args

    def dispatch_request(self, *args, **kwargs):
        meth = flask.request.method.lower()
        if meth == 'head':
            meth = 'get'

        assert self.cmd in self.operations, \
            "Unimplemented command ({0}) for {1}".format(
                self.cmd,
                str(self.__class__.__name__)
            )

        has_args, has_id = self.check_args(**kwargs)

        assert (self.cmd in self.operations and
                (has_id and len(self.operations[self.cmd]) > 0 and
                 meth in self.operations[self.cmd][0]) or
                (not has_id and len(self.operations[self.cmd]) > 1 and
                 meth in self.operations[self.cmd][1]) or
                (len(self.operations[self.cmd]) > 2 and
                 meth in self.operations[self.cmd][2])), \
            "Unimplemented method ({0}) for command ({1}), which {2} an id".format(
                meth, self.cmd,
                'requires' if has_id else 'does not require'
            )

        meth = self.operations[self.cmd][0][meth] if has_id else \
            self.operations[self.cmd][1][meth] if has_args and \
                                                  meth in self.operations[self.cmd][1] else \
                self.operations[self.cmd][2][meth]

        method = getattr(self, meth, None)

        if method is None:
            return make_json_response(
                status=406,
                success=0,
                errormsg=gettext(
                    "Unimplemented method ({0}) for this url ({1})".format(
                        meth, flask.request.path)
                )
            )

        return method(*args, **kwargs)

    @classmethod
    def register_node_view(cls, blueprint):
        cls.blueprint = blueprint
        id_url, url = cls.get_node_urls()

        commands = cls.generate_ops()

        for c in commands:
            if c['with_id']:
                blueprint.add_url_rule(
                    '/{0}{1}'.format(
                        c['cmd'], id_url if c['req'] else url
                    ),
                    view_func=cls.as_view(
                        '{0}{1}'.format(
                            c['cmd'], '_id' if c['req'] else ''
                        ),
                        cmd=c['cmd']
                    ),
                    methods=c['methods']
                )
            else:
                blueprint.add_url_rule(
                    '/{0}'.format(c['cmd']),
                    view_func=cls.as_view(
                        '{0}'.format(c['cmd']), cmd=c['cmd']
                    ),
                    methods=c['methods']
                )

    def module_js(self, **kwargs):
        """
        This property defines (if javascript) exists for this node.
        Override this property for your own logic.
        """
        return flask.make_response(
            flask.render_template(
                "{0}/js/{0}.js".format(self.node_type)
            ),
            200, {'Content-Type': 'application/x-javascript'}
        )

    def children(self, *args, **kwargs):
        """Build a list of treeview nodes from the child nodes."""
        children = []

        for module in self.blueprint.submodules:
            children.extend(module.get_nodes(*args, **kwargs))
        # Return sorted nodes based on label
        return make_json_response(
            data=sorted(
                children, key=lambda c: c['label']
            )
        )

BaseDriver

class BaseDriver(object):
    """
    class BaseDriver(object):

    This is a base class for different server types.
    Inherit this class to implement different type of database driver
    implementation.

    (For PostgreSQL/EDB Postgres Advanced Server, we will be using psycopg2)

    Abstract Properties:
    -------- ----------
    * Version (string):
        Current version string for the database server

    Abstract Methods:
    -------- -------
    * get_connection(*args, **kwargs)
    - It should return a Connection class object, which may/may not be
      connected to the database server.

    * release_connection(*args, **kwargs)
    - Implement the connection release logic

    * gc()
    - Implement this function to release the connections assigned in the
      session, which has not been pinged from more than the idle timeout
      configuration.
    """

    @abstractproperty
    def Version(cls):
        pass

    @abstractmethod
    def get_connection(self, *args, **kwargs):
        pass

    @abstractmethod
    def release_connection(self, *args, **kwargs):
        pass

    @abstractmethod
    def gc(self):
        pass

BaseConnection

class BaseConnection(object):
    """
    class BaseConnection(object)

        It is a base class for database connection. A different connection
        drive must implement this to expose abstract methods for this server.

        General idea is to create a wrapper around the actual driver
        implementation. It will be instantiated by the driver factory
        basically. And, they should not be instantiated directly.


    Abstract Methods:
    -------- -------
    * connect(**kwargs)
      - Define this method to connect the server using that particular driver
        implementation.

    * execute_scalar(query, params, formatted_exception_msg)
      - Implement this method to execute the given query and returns single
        datum result.

    * execute_async(query, params, formatted_exception_msg)
      - Implement this method to execute the given query asynchronously and returns result.

    * execute_void(query, params, formatted_exception_msg)
      - Implement this method to execute the given query with no result.

    * execute_2darray(query, params, formatted_exception_msg)
      - Implement this method to execute the given query and returns the result
        as a 2 dimensional array.

    * execute_dict(query, params, formatted_exception_msg)
      - Implement this method to execute the given query and returns the result
        as an array of dict (column name -> value) format.

    * def async_fetchmany_2darray(records=-1, formatted_exception_msg=False):
      - Implement this method to retrieve result of asynchronous connection and
        polling with no_result flag set to True.
        This returns the result as a 2 dimensional array.
        If records is -1 then fetchmany will behave as fetchall.

    * connected()
      - Implement this method to get the status of the connection. It should
        return True for connected, otherwise False

    * reset()
      - Implement this method to reconnect the database server (if possible)

    * transaction_status()
      - Implement this method to get the transaction status for this
        connection. Range of return values different for each driver type.

    * ping()
      - Implement this method to ping the server. There are times, a connection
        has been lost, but - the connection driver does not know about it. This
        can be helpful to figure out the actual reason for query failure.

    * _release()
      - Implement this method to release the connection object. This should not
        be directly called using the connection object itself.

      NOTE: Please use BaseDriver.release_connection(...) for releasing the
            connection object for better memory management, and connection pool
            management.

    * _wait(conn)
      - Implement this method to wait for asynchronous connection to finish the
        execution, hence - it must be a blocking call.

    * _wait_timeout(conn, time)
      - Implement this method to wait for asynchronous connection with timeout.
        This must be a non blocking call.

    * poll(formatted_exception_msg, no_result)
      - Implement this method to poll the data of query running on asynchronous
        connection.

    * cancel_transaction(conn_id, did=None)
      - Implement this method to cancel the running transaction.

    * messages()
      - Implement this method to return the list of the messages/notices from
        the database server.

    * rows_affected()
      - Implement this method to get the rows affected by the last command
        executed on the server.
    """

    ASYNC_OK = 1
    ASYNC_READ_TIMEOUT = 2
    ASYNC_WRITE_TIMEOUT = 3
    ASYNC_NOT_CONNECTED = 4
    ASYNC_EXECUTION_ABORTED = 5

    @abstractmethod
    def connect(self, **kwargs):
        pass

    @abstractmethod
    def execute_scalar(self, query, params=None, formatted_exception_msg=False):
        pass

    @abstractmethod
    def execute_async(self, query, params=None, formatted_exception_msg=True):
        pass

    @abstractmethod
    def execute_void(self, query, params=None, formatted_exception_msg=False):
        pass

    @abstractmethod
    def execute_2darray(self, query, params=None, formatted_exception_msg=False):
        pass

    @abstractmethod
    def execute_dict(self, query, params=None, formatted_exception_msg=False):
        pass

    @abstractmethod
    def async_fetchmany_2darray(self, records=-1, formatted_exception_msg=False):
        pass

    @abstractmethod
    def connected(self):
        pass

    @abstractmethod
    def reset(self):
        pass

    @abstractmethod
    def transaction_status(self):
        pass

    @abstractmethod
    def ping(self):
        pass

    @abstractmethod
    def _release(self):
        pass

    @abstractmethod
    def _wait(self, conn):
        pass

    @abstractmethod
    def _wait_timeout(self, conn, time):
        pass

    @abstractmethod
    def poll(self, formatted_exception_msg=True, no_result=False):
        pass

    @abstractmethod
    def status_message(self):
        pass

    @abstractmethod
    def rows_affected(self):
        pass

    @abstractmethod
    def cancel_transaction(self, conn_id, did=None):
        pass