Query the Data Delivery Network
Query the DDNThe 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
"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.
"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.
"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.
"designation", -- Name of the specific antenna tower location Station names in Blue are part of the National CORS Network.
"longitude", -- Westerly 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.
"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.
"latitude", -- Northerly 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.
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.
Query Your Local Engine
bash -c "$(curl -sL https://github.com/splitgraph/splitgraph/releases/latest/download/install.sh)"Read the installation docs.
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, 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 (like this repository), where the author has pushed Splitgraph Images to the repository, you can "clone" and/or "checkout" the data using sgr cloneand sgr checkout.
Cloning Data
Because ny-gov/continuously-operating-reference-stations-cors-j7t6-d8a8:latest is a Splitgraph Image, you can clone the data from Spltgraph Cloud to your local engine, where you can query it like any other Postgres database, using any of your existing tools.
First, install Splitgraph if you haven't already.
Clone the metadata with sgr clone
This will be quick, and does not download the actual data.
sgr clone ny-gov/continuously-operating-reference-stations-cors-j7t6-d8a8Checkout the data
Once you've cloned the data, you need to "checkout" the tag that you want. For example, to checkout the latest tag:
sgr checkout ny-gov/continuously-operating-reference-stations-cors-j7t6-d8a8:latestThis will download all the objects for the latest tag of ny-gov/continuously-operating-reference-stations-cors-j7t6-d8a8 and load them into the Splitgraph Engine. Depending on your connection speed and the size of the data, you will need to wait for the checkout to complete. Once it's complete, you will be able to query the data like you would any other Postgres database.
Alternatively, use "layered checkout" to avoid downloading all the data
The data in ny-gov/continuously-operating-reference-stations-cors-j7t6-d8a8:latest is 0 bytes. If this is too big to download all at once, or perhaps you only need to query a subset of it, you can use a layered checkout.:
sgr checkout --layered ny-gov/continuously-operating-reference-stations-cors-j7t6-d8a8:latestThis will not download all the data, but it will create a schema comprised of foreign tables, that you can query as you would any other data. Splitgraph will lazily download the required objects as you query the data. In some cases, this might be faster or more efficient than a regular checkout.
Read the layered querying documentation to learn about when and why you might want to use layered queries.
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.