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 apd_arrests table in this repository, by referencing it like:

"datahub-austintexas-gov/apd-arrests-9tem-ywan:latest"."apd_arrests"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "arrest_type_description", -- Describes the type of arrest, including on view arrest, summoned/cited, or taken into custody.
    "warrant_flag_1_0", -- An indicator used to indicate whether a subject was arrested and taken into custody. A value of '1' means the subject was arrested and taken into custody. A value of '0' means the subject was not arrested and taken into custody.
    "cite_release_flag_y_n", -- An indicator used to identify whether a subject was summoned or given a citation. A value of 'TRUE' means that the subject was either summoned or given a citation. A value of 'FALSE' means that the subject was not summoned or given a citation.
    "cite_release_flag_1_0", -- An indicator used to identify whether a subject was summoned or given a citation. A value of '1' means that the subject was either summoned or given a citation. A value of '0' means that the subject was not summoned or given a citation. 
    "arrest_sector", -- The Austin Police Department patrol sector where the arrest occurred.
    "case_report_number", -- The arrest report number is unique for an arrest. The arrest of one person may clear several cases and crimes, and the arrest of many persons may clear only one case.
    "occurred_date", -- The date on which the arrest took place. The arrest report is written on the day the arrest occurred, which may differ from the date the arrest incident occurred.
    "arrest_charges", -- The charge for which a subject was arrested.
    "census_block_group", -- The Census Block Group where the incident occurred.
    "subject_race_ethnicity", -- A person's self-identification with one or more social groups.
    "warrant_flag_y_n", -- An indicator used to indicate whether a subject was arrested and taken into custody. A value of 'TRUE' means the subject was arrested and taken into custody. A value of 'FALSE' means the subject was not arrested and taken into custody.
    "subject_gender" -- Gender identity refers to a person's sense of their own gender, whether male, female, or another category such as non-binary.
FROM
    "datahub-austintexas-gov/apd-arrests-9tem-ywan:latest"."apd_arrests"
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 datahub-austintexas-gov/apd-arrests-9tem-ywan with SQL in under 60 seconds.

This repository is an "external" repository. That means it's hosted elsewhere, in this case at datahub.austintexas.gov. When you querydatahub-austintexas-gov/apd-arrests-9tem-ywan: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 datahub.austintexas.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 \
  "datahub-austintexas-gov/apd-arrests-9tem-ywan" \
  --handler-options '{
    "domain": "datahub.austintexas.gov",
    "tables": {
        "apd_arrests": "9tem-ywan"
    }
}'

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, datahub-austintexas-gov/apd-arrests-9tem-ywan is just another Postgres schema.