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 ncvs_select_personal_population table in this repository, by referencing it like:

"priv-data-ojp-usdoj-gov/ncvs-select-personal-population-r4j4-fdwx:latest"."ncvs_select_personal_population"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "region", -- Region of respondent residence. The states have been divided into four groups or census regions, starting 1995 Q1.
    "marital", -- Respondent marital status
    "sex", -- Respondent sex
    "yearq", -- Year and quarter data was collected
    "educatn1", -- Respondent level of education
    "hincome2", -- Imputed income categories, starting 2017 Q1
    "year", -- Year data was collected
    "hincome1", -- Total income of all members of the household for the 12 months preceding the interview. Categories  available from 1993-2020 with imputed data, starting 2015 Q1.
    "race", -- Respondent race
    "msa", -- Classification of respondent residence based on the Office of Management and Budget definition of metropolitan statistical areas (MSAs)
    "idper", -- Unique person identifier
    "race_ethnicity", -- Respondent race and Hispanic origin
    "hispanic", -- Respondent Hispanic origin
    "citizen", -- Respondent citizenship status, starting 2017 Q1
    "wgtpercy", -- Population weight to use on person population data
    "locality", -- Location of household based on BJS geography definitions, starting 2020 Q1
    "ager", -- Respondent age on the last day of the month before the interview
    "educatn2", -- Respondent level of education, starting 2003 Q1
    "popsize", -- The size range for the place in which the housing unit is located
    "veteran" -- Respondent veteran status, starting in 2017
FROM
    "priv-data-ojp-usdoj-gov/ncvs-select-personal-population-r4j4-fdwx:latest"."ncvs_select_personal_population"
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 priv-data-ojp-usdoj-gov/ncvs-select-personal-population-r4j4-fdwx with SQL in under 60 seconds.

This repository is an "external" repository. That means it's hosted elsewhere, in this case at priv-data.ojp.usdoj.gov. When you querypriv-data-ojp-usdoj-gov/ncvs-select-personal-population-r4j4-fdwx: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 priv-data.ojp.usdoj.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 \
  "priv-data-ojp-usdoj-gov/ncvs-select-personal-population-r4j4-fdwx" \
  --handler-options '{
    "domain": "priv-data.ojp.usdoj.gov",
    "tables": {
        "ncvs_select_personal_population": "r4j4-fdwx"
    }
}'

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, priv-data-ojp-usdoj-gov/ncvs-select-personal-population-r4j4-fdwx is just another Postgres schema.