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 mta_metronorth_safety_and_grade_crossing_incidents table in this repository, by referencing it like:

"ny-gov/mta-metronorth-safety-and-grade-crossing-incidents-v7rp-a6ru:latest"."mta_metronorth_safety_and_grade_crossing_incidents"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "grade_crossing_incidents", -- Any impact between railroad on-track equipment and a highway user at a highway-rail grade crossing. The term “highway user” includes automobiles, buses, trucks, motorcycles, bicycles, farm vehicles, pedestrians, and all other modes of surface transportation motorized and un-motorized.
    "train_derailments", -- A derailment occurs when on-track equipment leaves the rail for a reason other than a collision, explosion, highway-rail grade crossing impact, etc.
    "employee_lost_time_days", -- The total number of calendar days employees’ treating medical professionals have determined that they cannot work due to a reportable occupation injury or illness. 
    "lost_time_accident_rate", -- The rate of reportable job-related incidents that result in the inability of an employee to perform full job duties for at least one working day beyond the day of the incident, per one hundred employees. 
    "customer_accident_rate", -- The number of reportable customer injuries per million customers.
    "train_collisions", -- A collision is defined as an impact between on-track equipment consists while both are on rails and where one of the consists is operating under train movement rules or is subject to the protection afforded to trains.
    "employee_lost_time_injury", -- The rate of reportable occupational injuries or illnesses, per 200,000 employee hours worked. 
    "month" -- The time period in which the Lost Time rates are being calculated (month and year). 
FROM
    "ny-gov/mta-metronorth-safety-and-grade-crossing-incidents-v7rp-a6ru:latest"."mta_metronorth_safety_and_grade_crossing_incidents"
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/mta-metronorth-safety-and-grade-crossing-incidents-v7rp-a6ru 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/mta-metronorth-safety-and-grade-crossing-incidents-v7rp-a6ru: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/mta-metronorth-safety-and-grade-crossing-incidents-v7rp-a6ru" \
  --handler-options '{
    "domain": "data.ny.gov",
    "tables": {
        "mta_metronorth_safety_and_grade_crossing_incidents": "v7rp-a6ru"
    }
}'

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/mta-metronorth-safety-and-grade-crossing-incidents-v7rp-a6ru is just another Postgres schema.