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 station_location_wave_dataset table in this repository, by referencing it like:
"novascotia-ca/station-location-wave-dataset-dhns-eqjr:latest"."station_location_wave_dataset"or in a full query, like:
SELECT
":id", -- Socrata column ID
"ensemble_interval", -- Time (seconds) between the beginning of one data recording profile and the next, where applicable
"first_bin_range", -- Distance (meters) between the sensing face of the instrument and the vertical center of the first recorded bin, where applicable
"bin_size", -- Vertical size (meters) of parcels from which current data are recorded throughout the water column, where applicable
"frequency", -- Frequency (kilohertz) of the acoustic signals generated by the instrument, where applicable
"model", -- Specific instrument model used to record waves data, where applicable
"deployment_duration", -- Number of days between first and last data readings
"deployment_longitude", -- Approximate longitude at which the instrument was deployed
"deployment_latitude", -- Approximate latitude at which the instrument was deployed
"deployment_time", -- Time at which the instrument was deployed and began recording
"lease", -- Identification number of Nova Scotia aquaculture lease within which deployment took place. N/A if not within a lease
"station_name", -- Description used to identify the approximate geographical area of the deployment
"deployment_id", -- Unique identifier assigned to each deployment
"geo_location",
"averaging_interval", -- Time (seconds) over which multiple recordings are taken and averaged during each ensemble, where applicable
"altitude", -- Approximate distance (meters) between the sensing face of the instrument and the sea floor where applicable
"depth", -- Approximate average distance (meters) between the sensing face of the instrument and the ocean surface, where applicable
"recovery_date", -- Date at which last data reading was collected
"deployment_sounding", -- Distance (meters) from sea surface to the sea floor at location at which the instrument was deployed, where applicable
"deployment_date", -- Date on which the instrument was deployed and began recording
"waterbody", -- Waterbody into which the instrument was deployed
"county", -- County in which the deployment took place
"pings_per_ensemble" -- Number of individual recordings taken and averaged over the course of the averaging interval, where applicable
FROM
"novascotia-ca/station-location-wave-dataset-dhns-eqjr:latest"."station_location_wave_dataset"
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 novascotia-ca/station-location-wave-dataset-dhns-eqjr 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 novascotia-ca/station-location-wave-dataset-dhns-eqjr: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 novascotia-ca/station-location-wave-dataset-dhns-eqjrCheckout 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 novascotia-ca/station-location-wave-dataset-dhns-eqjr:latestThis will download all the objects for the latest tag of novascotia-ca/station-location-wave-dataset-dhns-eqjr 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 novascotia-ca/station-location-wave-dataset-dhns-eqjr: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 novascotia-ca/station-location-wave-dataset-dhns-eqjr: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, novascotia-ca/station-location-wave-dataset-dhns-eqjr is just another Postgres schema.