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 civil_service_list_certification table in this repository, by referencing it like:

"cityofnewyork-us/civil-service-list-certification-a9md-ynri:latest"."civil_service_list_certification"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "list_title_desc", -- A descriptive name that identifies a civil service title.  
    "mi", -- An eligible candidate’s middle initial (MI) as it appears on their application. 
    "list_title_code", -- A five (5) digit number that corresponds to and represents a civil service title. 
    "exam_no", -- A four (4) digit number that identifies a civil service examination. 
    "salary", -- The hiring salary for a title.   
    "first_name", -- An eligible candidate’s first name as it appears on their application. 
    "cert_date", -- The date on which a Certification is created by the Certification Unit at the Department of Citywide Administrative Services.     
    "request_date", -- The date on which an appointing Agency submits a request for a Certification.   
    "list_no", -- An eligible candidate’s placement on a given list as of the business day that the data set is populated.  
    "list_agency_desc", -- The name of an appointing Agency. 
    "cert_issue_no", -- A system generated identifier (number or “No”) that is unique to a specific Certification.  
    "no_certified", -- Represents the number (“No”) of eligible candidates sent to an appointing agency as part of the Certification.   
    "no_vacancies", -- Represent the number (“No”) of vacancies an agency is approved to fill. 
    "cert_expiration_date", -- The date on which a Certification is scheduled to expire.       
    "sel_cert_description", -- A certification sequence number (“Cert Seq No”) indicates an eligible candidate’s placement on a Certification. 
    "cert_seq_no", -- A certification sequence number (“Cert Seq No”) indicates an eligible candidate’s placement on a Certification. 
    "no_requested", -- Represents the number (“No”) of eligible candidates requested by an appointing Agency to fill vacancies.  
    "reissue_date", -- The date on which a Certification will be extended beyond its original expiration date.   
    "provisional_replacement", -- Indicates if a Certification is being  issued to replace a provisional (“Prov”) employee (not permanent) 
    "last_name", -- An eligible candidate’s last name as it appears on their application.  
    "list_agency_code" -- A three (3) digit number used to identify an appointing agency (For Promotion List Only). 
FROM
    "cityofnewyork-us/civil-service-list-certification-a9md-ynri:latest"."civil_service_list_certification"
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/civil-service-list-certification-a9md-ynri 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/civil-service-list-certification-a9md-ynri: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/civil-service-list-certification-a9md-ynri" \
  --handler-options '{
    "domain": "data.cityofnewyork.us",
    "tables": {
        "civil_service_list_certification": "a9md-ynri"
    }
}'

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/civil-service-list-certification-a9md-ynri is just another Postgres schema.