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 city_of_memphis_parks_spatial_data table in this repository, by referencing it like:

"memphistn-gov/city-of-memphis-parks-spatial-data-aeu5-vwkq:latest"."city_of_memphis_parks_spatial_data"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "zipcode", -- Zip code that park is located in 
    "inside_y", -- Variable used for mapping in GIS
    "inside_x", -- Variable used for mapping in GIS
    "restrooms", -- Whether park has restrooms
    "grilles", -- Whether park has grills for cooking/grilling
    "acres_park", -- Park area in acres
    "park_local", -- Park local owner/operator (City of Memphis) - from ParkServe
    "parkid", -- Unique park ID for ParkServe(R), a national project focused on parks and the 10-minute walk area around them. Learn more at https://www.tpl.org/parkserve
    "location", -- Park address
    "additional", -- Any additional assets at each park
    "shape_st_1", -- Geographic variable used for mapping parks in GIS
    "pavilions", -- Whether park has pavilion
    "fountains", -- Whether park has fountain
    "shape_st_2", -- Geographic variable used for mapping parks in GIS
    "council_di", -- Council district park is located in
    "basketball", -- Whether park has basketball court
    "census_tra", -- 2010 US Census tract that park is located in
    "trash", -- Whether park has trash facilities
    "ballfield", -- Whether park has ballfield
    ":@computed_region_me95_vbw4",
    ":@computed_region_xf2b_u4zq",
    ":@computed_region_gxae_hf64",
    "park_nam_1", -- Park Name
    "shape_stle", -- Geographic variable used for mapping parks in GIS
    "park_manag", -- Park manager (City) - from ParkServe
    "shape_star", -- Geographic variable used for mapping parks in GIS
    "tennis_cou", -- Whether park has tennis court
    "picnic_tab", -- Whether park has picnic tables
    "point", -- Point coordinates, used for mapping parks in GIS
    "play_equip", -- Whether park has play equipment
    "walking_tr", -- Whether park has walking trail
    "facilities", -- General description of park facilities 
    "benches", -- Whether park has bench(es)
    "pools", -- Whether park has swimming pool - If yes, indoor or outdoor
    "play_groun", -- Whether park has playground
    "off_street", -- Whether off-street parking is available at the park
    "gistrkrid", -- ID used for mapping
    "concession", -- Whether park has concession stand (food/beverage)
    "park_owner" -- Park owner (City) - from ParkServe
FROM
    "memphistn-gov/city-of-memphis-parks-spatial-data-aeu5-vwkq:latest"."city_of_memphis_parks_spatial_data"
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 memphistn-gov/city-of-memphis-parks-spatial-data-aeu5-vwkq with SQL in under 60 seconds.

This repository is an "external" repository. That means it's hosted elsewhere, in this case at data.memphistn.gov. When you querymemphistn-gov/city-of-memphis-parks-spatial-data-aeu5-vwkq: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.memphistn.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 \
  "memphistn-gov/city-of-memphis-parks-spatial-data-aeu5-vwkq" \
  --handler-options '{
    "domain": "data.memphistn.gov",
    "tables": {
        "city_of_memphis_parks_spatial_data": "aeu5-vwkq"
    }
}'

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, memphistn-gov/city-of-memphis-parks-spatial-data-aeu5-vwkq is just another Postgres schema.