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 recalls_data table in this repository, by referencing it like:

"datahub-transportation-gov/recalls-data-6axg-epim:latest"."recalls_data"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "recall_link", -- Displays a link for Information on the recall on the NHTSA web site.
    "corrective_action", -- Displays a brief description of the proposed solution to the recall.
    "completion_rate", -- Displays a percentage that indicates how many units of the recalled population have been remedied. Blank value indicates it has not been reported
    "component", -- Displays the name of the defective/noncompliant component associated with the product.
    "defect_summary", -- Displays a summary of the problem that prompted the recall. The description includes the product make, model, and model year.
    "do_not_drive", -- Advisory for owners of these vehicles should park them immediately until the recall remedy is completed.
    "nhtsa_id", -- NHTSA CAMPAIGN NUMBER, Displays the recall number. The recall number is composed of the two-digit year, the one-character recall type, the two-character recall sub-type, the three-character recall number for the year, and the three-character recall subject.
    "subject", -- Displays the name of the product and the defect that is the subject of the recall.
    "manufacturer", -- Displays the name of the product manufacturer.
    "potentially_affected", -- Displays the number of products that are potentially affected by the recall.
    "report_received_date", -- Displays the date that NHTSA received the Defect and Noncompliance report from the manufacturer.
    "consequence_summary", -- Displays a summary of the consequences of the defect or noncompliance.
    "mfr_campaign_number", -- Displays the identification number assigned to the recall by the manufacturer.
    "recall_type", -- Displays the recall category. If the recall involves a noncompliant product, the word "compliance" appears in this field. If the recall involves a defective product, the word "Defect" appears. If the recall involves a product that requires a safety improvement, the phrase "safety improvement" appears.
    "fire_risk_when_parked" -- Advisory for owners to park outside and away from structures because vehicles can catch fire.
FROM
    "datahub-transportation-gov/recalls-data-6axg-epim:latest"."recalls_data"
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 datahub-transportation-gov/recalls-data-6axg-epim with SQL in under 60 seconds.

This repository is an "external" repository. That means it's hosted elsewhere, in this case at datahub.transportation.gov. When you querydatahub-transportation-gov/recalls-data-6axg-epim: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 datahub.transportation.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 \
  "datahub-transportation-gov/recalls-data-6axg-epim" \
  --handler-options '{
    "domain": "datahub.transportation.gov",
    "tables": {
        "recalls_data": "6axg-epim"
    }
}'

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, datahub-transportation-gov/recalls-data-6axg-epim is just another Postgres schema.