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 traffic_control_device_inventory table in this repository, by referencing it like:

"ny-gov/traffic-control-device-inventory-8fht-3ajj:latest"."traffic_control_device_inventory"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "owning_region", -- DOT Region that owns the device
    "latitude_utm_y_meters", -- UTM X and UTM Y are the location coordinates in the Universal Transverse Mercator (UTM) coordinate system. Y-Coordinate (north-south). Each unit value equals one meter. Numbers become increasingly large to the north.
    "device_number", -- A number that uniquely identifies the device. The number is usually visible somewhere on the device
    "main_route", -- Primary route where the device is located
    "intersecting_route", -- Intersecting route where the device is located
    "longitude_utm_x_meters", -- UTM X and UTM Y are the location coordinates in the Universal Transverse Mercator (UTM) coordinate system. X-Coordinate (east-west). Each unit value equals one meter. Numbers become increasingly large to the east.
    "maintenance_responsibility", -- Identifies the workforce that should be responding when there are issues with the device
    "county", -- County where device is located
    "device_type", -- Identifies the type of device. Specific Devices are defined below:  3-color signal - A signal device by which traffic is alternately directed to stop and permitted to proceed; street light - provides illumination to a highway or bridge; flasher; beacon - An array of two or more yellow flashing indications facing in one direction; navigation lights - attached to a highway structure for the purpose of defining the navigational channel of a water system below; ITS (Intelligent Transportation System) locations - include but are not limited to dynamic message boards and vehicle counting equipment.; and master - a signal that controls a group of signals
    "device_purpose", -- Describes the purpose of the device. Values (further described in the attached Data Dictionary) are: standard, round about, no controller, sign, emergency,  special purpose, navigation lights, pedestrian, ITS camera, bridge lighting, RR track lighting, temporary signal, one-way signal, ITS loop counting station, railroad crossing, portable signal, ITS equipment site, dynamic message board, school, street light, canal, drawbridge, and ITS detection. 
    "location", -- Identifies the location of the device in descriptive terms
    "device_priority", -- Identifies how important the signal is necessary for prioritizing repairs and response
    "municipality", -- Municipality where device is located
    "maintaining_region" -- DOT Region that maintains the device
FROM
    "ny-gov/traffic-control-device-inventory-8fht-3ajj:latest"."traffic_control_device_inventory"
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 ny-gov/traffic-control-device-inventory-8fht-3ajj with SQL in under 60 seconds.

This repository is an "external" repository. That means it's hosted elsewhere, in this case at data.ny.gov. When you queryny-gov/traffic-control-device-inventory-8fht-3ajj: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.ny.gov, 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 \
  "ny-gov/traffic-control-device-inventory-8fht-3ajj" \
  --handler-options '{
    "domain": "data.ny.gov",
    "tables": {
        "traffic_control_device_inventory": "8fht-3ajj"
    }
}'

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, ny-gov/traffic-control-device-inventory-8fht-3ajj is just another Postgres schema.