Query the Data Delivery Network

The easiest way to query any data on Splitgraph is via the "Data Delivery Network" (DDN). The DDN is a single endpoint that speaks the PostgreSQL wire protocol. Any Splitgraph user can connect to it at data.splitgraph.com:5432 and query any version of over 40,000 datasets that are hosted or proxied by Splitgraph.

For example, you can query the beach_weather_stations_automated_sensors table in this repository, by referencing it like:

"cityofchicago/beach-weather-stations-automated-sensors-k7hf-8y75:latest"."beach_weather_stations_automated_sensors"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "station_name",
    "measurement_timestamp", -- The date and time when the measurements were taken.
    "measurement_id", -- A unique record ID made up of the Station Name and Measurement Timestamp.
    "solar_radiation", -- Solar radiation in watts per square meter.
    "air_temperature", -- Air Temperature in Celsius degrees.
    "interval_rain", -- Rain since the last hourly measurement, in mm.
    "humidity", -- Percent relative humidity.
    "wind_speed", -- Wind speed in meters per second at the time the record was reported.
    "wet_bulb_temperature", -- Wet bulb temperature in Celsius degrees.
    "precipitation_type", -- 0   = No precipitation  60 = Liquid precipitation, e.g. rain       - Ice, hail and sleet are transmitted as rain (60). 70 = Solid precipitation, e.g. snow  40 = unspecified precipitation
    "rain_intensity", -- Rain intensity in mm per hour.
    "wind_direction", -- Wind direction in degrees.
    "measurement_timestamp_label", -- The Last Updated value in text format, suitable for use in the Visualize function.
    "total_rain", -- Total rain since midnight in mm.
    "maximum_wind_speed", -- Maximum wind speed in the two-minute period immediately preceding the time the record was reported.
    "barometric_pressure", -- Barometric pressure in hPa.
    "heading", -- The current heading of the wind-measurement unit.  The ideal value to get the most accurate measurements is true north (0 degrees) and the unit is manually adjusted, as necessary, to keep it close to this heading
    "battery_life" -- Battery voltage, an indicator of remaining battery life used by the Chicago Park District to know when batteries should be replaced.
FROM
    "cityofchicago/beach-weather-stations-automated-sensors-k7hf-8y75:latest"."beach_weather_stations_automated_sensors"
LIMIT 100;

Connecting to the DDN is easy. All you need is an existing SQL client that can connect to Postgres. As long as you have a SQL client ready, you'll be able to query cityofchicago/beach-weather-stations-automated-sensors-k7hf-8y75 with SQL in under 60 seconds.

This repository is an "external" repository. That means it's hosted elsewhere, in this case at data.cityofchicago.org. When you querycityofchicago/beach-weather-stations-automated-sensors-k7hf-8y75:latest on the DDN, we "mount" the repository using the socrata mount handler. The mount handler proxies your SQL query to the upstream data source, translating it from SQL to the relevant language (in this case SoQL).

We also cache query responses on the DDN, but we run the DDN on multiple nodes so a CACHE_HIT is only guaranteed for subsequent queries that land on the same node.

Query Your Local Engine

bash -c "$(curl -sL https://github.com/splitgraph/splitgraph/releases/latest/download/install.sh)"

Splitgraph Cloud is built around Splitgraph Core (GitHub), which includes a local Splitgraph Engine packaged as a Docker image. Splitgraph Cloud is basically a scaled-up version of that local Engine. When you query the Data Delivery Network or the REST API, we mount the relevant datasets in an Engine on our servers and execute your query on it.

It's possible to run this engine locally. You'll need a Mac, Windows or Linux system to install sgr, and a Docker installation to run the engine. You don't need to know how to actually use Docker; sgrcan manage the image, container and volume for you.

There are a few ways to ingest data into the local engine.

For external repositories (like this repository), the Splitgraph Engine can "mount" upstream data sources by using sgr mount. This feature is built around Postgres Foreign Data Wrappers (FDW). You can write custom "mount handlers" for any upstream data source. For an example, we blogged about making a custom mount handler for HackerNews stories.

For hosted datasets, where the author has pushed Splitgraph Images to the repository, you can "clone" and/or "checkout" the data using sgr cloneand sgr checkout.

Mounting Data

This repository is an external repository. It's not hosted by Splitgraph. It is hosted by data.cityofchicago.org, and Splitgraph indexes it. This means it is not an actual Splitgraph image, so you cannot use sgr clone to get the data. Instead, you can use the socrata adapter with the sgr mount command. Then, if you want, you can import the data and turn it into a Splitgraph image that others can clone.

First, install Splitgraph if you haven't already.

Mount the table with sgr mount

sgr mount socrata \
  "cityofchicago/beach-weather-stations-automated-sensors-k7hf-8y75" \
  --handler-options '{
    "domain": "data.cityofchicago.org",
    "tables": {
        "beach_weather_stations_automated_sensors": "k7hf-8y75"
    }
}'

That's it! Now you can query the data in the mounted table like any other Postgres table.

Query the data with your existing tools

Once you've loaded the data into your local Splitgraph engine, you can query it with any of your existing tools. As far as they're concerned, cityofchicago/beach-weather-stations-automated-sensors-k7hf-8y75 is just another Postgres schema.