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 copa_cases_by_complainant_or_subject table in this repository, by referencing it like:

"cityofchicago/copa-cases-by-complainant-or-subject-vnz2-rmie:latest"."copa_cases_by_complainant_or_subject"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "police_shooting", -- Whether or not the case is a police shooting.
    "age_of_complainant", -- The age of the complainant or subject.
    "current_status", -- The current status of the case investigation, as of the date the data were last published.
    "complaint_hour", -- The hour of the day component of COMPLAINT_DATE.
    "beat", -- The CPD beat in which the incident occurred. If more than one beat was involved, the values are separated by the pipe (|) character.
    "assignment", -- The jurisdictional assignment for the complaint case.
    "race_of_complainant", -- The race or ethnicity of the complainant or subject.
    "case_type", -- Whether a case is a complaint, a notification, or miscellaneous.
    "sex_of_complainant", -- The sex of the complainant or subject.
    "complaint_day", -- The day of the week component of COMPLAINT_DATE. Sunday=1
    "complaint_month", -- The month component of COMPLAINT_DATE.
    "complaint_date", -- The date that the complaint or notification was made to IPRA/COPA and the record was created.
    "current_category", -- The category of the primary allegation against the involved CPD member.
    "finding_code", -- The overall current case finding, ranked by the following hierarchy: Sustained, Not Sustained, Unfounded, Exonerated, No Affidavit, and No Finding.  “Current_Finding” means that even after COPA has completed an investigation and made a recommended finding, the finding can change given post-COPA processes, including Police Department review, Police Board adjudication, and grievance and arbitration processes.
    "log_no" -- A unique identifier for the case record. The log number can be used to link records in other datasets that contain a log number column.
FROM
    "cityofchicago/copa-cases-by-complainant-or-subject-vnz2-rmie:latest"."copa_cases_by_complainant_or_subject"
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 cityofchicago/copa-cases-by-complainant-or-subject-vnz2-rmie with SQL in under 60 seconds.

This repository is an "external" repository. That means it's hosted elsewhere, in this case at data.cityofchicago.org. When you querycityofchicago/copa-cases-by-complainant-or-subject-vnz2-rmie: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.cityofchicago.org, 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 \
  "cityofchicago/copa-cases-by-complainant-or-subject-vnz2-rmie" \
  --handler-options '{
    "domain": "data.cityofchicago.org",
    "tables": {
        "copa_cases_by_complainant_or_subject": "vnz2-rmie"
    }
}'

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, cityofchicago/copa-cases-by-complainant-or-subject-vnz2-rmie is just another Postgres schema.