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 mayors_office_of_operations_demographic_survey table in this repository, by referencing it like:

"cityofnewyork-us/mayors-office-of-operations-demographic-survey-tap2-dwrw:latest"."mayors_office_of_operations_demographic_survey"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "survey_status", -- Indicates that on-line survey has been finalized. ; Complete or Incomplete
    "data_source", -- Paper or On-line
    "dt_submitted", -- The date the survey was completed; The on-line version is automated.  Paper survey the date can be ignored, entered incorrectly or the text may be ilegible.
    "survey_instance_id", -- A number that links all rows of a returned survey.;  Results are stored in a columnar fashion. Group by survey_instance_id to get all the Q/A pairs for a given instance of a survey.
    "survey_number", -- A number unique to each version of a survey; When analyzing the results, consider that rows with different survey_numbers may have different sets of questions and answers.
    "question", -- The text of the survey question
    "id", -- Primary Key
    "create_dt", -- The date the survey was processed; System generated.  For on-line it is the time the user clicked complete.  For paper surveys it is the time that survey was loaded into a database (usually monthly).
    "survey_language", -- The language of the survey; Both the paper and on-line version exist in 11 languages.
    "answer", -- The survey answer; May be entered as free-form text for some questions
    "answer_is_optional" -- Indicates an optional question; Valid on-line only.  All answers are optional for the paper version.
FROM
    "cityofnewyork-us/mayors-office-of-operations-demographic-survey-tap2-dwrw:latest"."mayors_office_of_operations_demographic_survey"
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 cityofnewyork-us/mayors-office-of-operations-demographic-survey-tap2-dwrw with SQL in under 60 seconds.

This repository is an "external" repository. That means it's hosted elsewhere, in this case at data.cityofnewyork.us. When you querycityofnewyork-us/mayors-office-of-operations-demographic-survey-tap2-dwrw: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.cityofnewyork.us, 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 \
  "cityofnewyork-us/mayors-office-of-operations-demographic-survey-tap2-dwrw" \
  --handler-options '{
    "domain": "data.cityofnewyork.us",
    "tables": {
        "mayors_office_of_operations_demographic_survey": "tap2-dwrw"
    }
}'

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, cityofnewyork-us/mayors-office-of-operations-demographic-survey-tap2-dwrw is just another Postgres schema.