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 trips_by_distance table in this repository, by referencing it like:

"bts-gov/trips-by-distance-w96p-f2qv:latest"."trips_by_distance"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "trips_10_25", -- Number of trips by residents greater than 10 miles and shorter than 25 miles (10 ≤ trip distance < 25 miles)
    "trips_5_10", -- Number of trips by residents greater than 5 miles and shorter than 10 miles (5 ≤ trip distance < 10 miles)
    "trips_250_500", -- Number of trips by residents greater than 250 miles and shorter than 500 miles (250 ≤ trip distance < 500 miles)
    "date", -- Date
    "trips_100_250", -- Number of trips by residents greater than 100 miles and shorter than 250 miles (100 ≤ trip distance < 250 miles)
    "trips_50_100", -- Number of trips by residents greater than 50 miles and shorter than 100 miles (50 ≤ trip distance < 100 miles)
    "week",
    "row_id", -- Unique row identifier
    "trips", -- Number of trips made by residents, i.e., movements that include a stay of longer than 10 minutes at an anonymized location away from home.
    "pop_not_stay_at_home", -- Number of residents not staying at home
    "state_fips", -- Two-digit FIPS state code
    "trips_25_50", -- Number of trips by residents greater than 25 miles and shorter than 50 miles (25 ≤ trip distance < 50 miles)
    "trips_1_3", -- Number of trips by residents greater than one mile and shorter than 3 miles (1 ≤ trip distance < 3 miles)
    "trips_1", -- Number of trips by residents shorter than one mile
    "pop_stay_at_home", -- Number of residents staying at home, i.e., persons who make no trips with a trip end more than one mile away from home
    "state_code", -- State postal code
    "trips_500", -- Number of trips by residents greater than 500 miles (trip distance ≥ 500 miles)
    "trips_3_5", -- Number of trips by residents greater than 3 miles and shorter than 5 miles (3 ≤ trip distance < 5 miles)
    "county", -- County name
    "county_fips", -- Five-digit FIPS county code
    "month",
    "level" -- Indicates National, State, or County level metrics
FROM
    "bts-gov/trips-by-distance-w96p-f2qv:latest"."trips_by_distance"
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 bts-gov/trips-by-distance-w96p-f2qv with SQL in under 60 seconds.

This repository is an "external" repository. That means it's hosted elsewhere, in this case at data.bts.gov. When you querybts-gov/trips-by-distance-w96p-f2qv: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.bts.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 \
  "bts-gov/trips-by-distance-w96p-f2qv" \
  --handler-options '{
    "domain": "data.bts.gov",
    "tables": {
        "trips_by_distance": "w96p-f2qv"
    }
}'

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, bts-gov/trips-by-distance-w96p-f2qv is just another Postgres schema.