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 continuously_operating_reference_stations_cors table in this repository, by referencing it like:

"ny-gov/continuously-operating-reference-stations-cors-j7t6-d8a8:latest"."continuously_operating_reference_stations_cors"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "longitude", -- Westerly coordinate location of the tower position for establishing the NYS Plane Coordinate system of 1983 (North American Datum of 1983, NAD83).
    ":@computed_region_yamh_8v7k", -- This column was automatically created in order to record in what polygon from the dataset 'NYS Municipal Boundaries' (yamh-8v7k) the point in column 'georeference' is located.  This enables the creation of region maps (choropleths) in the visualization canvas and data lens.
    "position_source", -- Positions for the sites with the Position Source labeled ‘NGS’ should match the NGS published coordinates. Positions for the sites below with the Position Source labeled ‘OPA’ have not been published by NGS. Positions were computed by processing daily 24 hour data sets with 30 second observations in a GPS baseline processing/least squares network adjustment program, then averaging a minimum of 10 daily solutions from that program.
    "georeference", -- Open Data platform-generated geocoding information from supplied address components.  Point-type location is the centroid of the address components provided and does not reflect a specific address if the street address component is not provided.  Point-type location is supplied in "POINT (<geocoded longitude> <geocoded latitude>)" format.
    "antenna_type", -- Specific information on the technical type of equipment. CORS defined in NAD83(2011) use absolute antenna calibrations. Absolute values should be used when processing data with CORS coordinates in NAD 83(2011) EPOCH 2010.0.
    "ellipsoid_height", -- Elevation control of the station. NA2011 yields ellipsoid heights that are not directly connected to NAVD88, therefore a GEOID model could be used to estimate NAVD88 heights. Depending upon required survey accuracy, the user must determine required connections to local vertical datum’s including NAVD88.
    "latitude", -- Northerly coordinate location of the tower position for establishing the NYS Plane Coordinate system of 1983 (North American Datum of 1983, NAD83).
    "site_number", -- Real Time Site Number, this number is included in real time data streams so that a rover knows which reference station is being used.
    "ngs_site_id", -- Location identification 4 character ID. Positions     for the sites below with the Position Source labeled ‘NGS’ should match the NGS published coordinates.
    "designation" -- Name of the specific antenna tower location Station names in Blue are part of the National CORS Network.
FROM
    "ny-gov/continuously-operating-reference-stations-cors-j7t6-d8a8:latest"."continuously_operating_reference_stations_cors"
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 ny-gov/continuously-operating-reference-stations-cors-j7t6-d8a8 with SQL in under 60 seconds.

This repository is an "external" repository. That means it's hosted elsewhere, in this case at data.ny.gov. When you queryny-gov/continuously-operating-reference-stations-cors-j7t6-d8a8: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.ny.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 \
  "ny-gov/continuously-operating-reference-stations-cors-j7t6-d8a8" \
  --handler-options '{
    "domain": "data.ny.gov",
    "tables": {
        "continuously_operating_reference_stations_cors": "j7t6-d8a8"
    }
}'

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, ny-gov/continuously-operating-reference-stations-cors-j7t6-d8a8 is just another Postgres schema.