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 offenders_released_from_iowa_prisons table in this repository, by referencing it like:

"mydata-iowa-gov/offenders-released-from-iowa-prisons-runv-jsix:latest"."offenders_released_from_iowa_prisons"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "admission_date", -- Date of when the Offender first came to our institution
    "offense_subtype", -- Further classification of the convicted offense.
    "age_at_release", -- Age of offender when released from the institution
    "closure_type", -- The short reason why the offender left our institution
    "release_date", -- The date the offender was released from prison.
    "months_served", -- Number of months the offender spent in prison as of the release date
    "jurisdiction", -- The county in which the offender committed the offense
    "offense_class", -- Conviction maximum penalties: A Felony = Life; B Felony = 25 or 50 years; C Felony = 10 years; D Felony = 5 years; Aggravated Misdemeanor = 2 years; Serious Misdemeanor = 1 year; Simple Misdemeanor = 30 days 
    "offense_code", -- The code found in the law book for the offense that had been convicted. 
    "institution_name", -- The last institution where the offender spent their time.
    "offense_type", -- General category of the conviction that was committed.
    "sex", -- Offender's sex.
    "supervision_status", -- Offender's Supervision Status
    "fiscal_year_released", -- Fiscal Years run from July 1 - June 30 and are named after the calendar year for which they end.  For example, July 1, 2015 -  June 30, 2016 is considered Fiscal Year 2016.  This data reflects the fiscal year the offender was released from prison.
    "offender_number", -- Unique ID for the offender.
    "record_id", -- Unique ID for the record
    "race_ethnicity", -- Offender's race and ethnicity.
    "offense_description" -- General description of the conviction that was committed.
FROM
    "mydata-iowa-gov/offenders-released-from-iowa-prisons-runv-jsix:latest"."offenders_released_from_iowa_prisons"
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 mydata-iowa-gov/offenders-released-from-iowa-prisons-runv-jsix with SQL in under 60 seconds.

This repository is an "external" repository. That means it's hosted elsewhere, in this case at mydata.iowa.gov. When you querymydata-iowa-gov/offenders-released-from-iowa-prisons-runv-jsix: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 mydata.iowa.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 \
  "mydata-iowa-gov/offenders-released-from-iowa-prisons-runv-jsix" \
  --handler-options '{
    "domain": "mydata.iowa.gov",
    "tables": {
        "offenders_released_from_iowa_prisons": "runv-jsix"
    }
}'

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, mydata-iowa-gov/offenders-released-from-iowa-prisons-runv-jsix is just another Postgres schema.