Implementing a custom Virtual Server

You can connect Perspective to any data source by subclassing VirtualServerHandler and wrapping it with VirtualServer.

For background on virtual servers, see the Virtual Servers overview.

Example

from perspective import VirtualServerHandler, VirtualServer

class MyModel(VirtualServerHandler):
    def get_features(self):
        return {
            "group_by": True,
            "split_by": False,
            "sort": True,
            "filter_ops": {
                "string": ["==", "!=", "contains"],
                "float": ["==", "!=", ">", "<"],
            },
            "aggregates": {
                "float": ["sum", "avg", "count"],
                "string": ["count"],
            },
        }

    def get_hosted_tables(self):
        return ["my_table"]

    def table_schema(self, table_name):
        return {"name": "string", "price": "float"}

    def table_size(self, table_name):
        return 1000

    def table_make_view(self, table_name, view_id, config):
        # Translate `config` (group_by, sort, filter, etc.) into a
        # query against your data source. Store the query keyed by
        # `view_id` for later data retrieval.
        pass

    def view_delete(self, view_id):
        # Clean up resources for this view
        pass

    def view_get_data(self, view_id, start_row, end_row, start_col, end_col, ctx):
        # Execute the stored query with the given row/column window.
        # Push results via `ctx`.
        pass

The VirtualServer instance can then be passed to a Tornado, Starlette, or AIOHTTP handler just like a regular Server:

from perspective.handlers.tornado import PerspectiveTornadoHandler

app = tornado.web.Application([
    (r"/websocket", PerspectiveTornadoHandler, {"perspective_server": VirtualServer(MyModel)}),
])