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 cambridge_community_wide_greenhouse_gas_inventory table in this repository, by referencing it like:
"cambridgema-gov/cambridge-community-wide-greenhouse-gas-inventory-eiuf-6ksy:latest"."cambridge_community_wide_greenhouse_gas_inventory"or in a full query, like:
SELECT
":id", -- Socrata column ID
"nitrous_oxide", -- Emissions of the greenhouse gas nitrous oxide (N2O). Units are megatonnes, or one million metric tons.
"methane_emissions", -- Emissions of the greenhouse gas methane (CH4). Units are megatonnes, or one million metric tons.
"scope", -- Greenhouse gas accounting protocols tend to assign a "scope" of 1, 2, or 3 to greenhouse gas emissions. The scope indicates whether the emissions derive from a source that is directly or indirectly controlled by Cambridge. Scope 1: All direct GHG emissions. Scope 2: Indirect GHG emissions from consumption of purchased electricity, heat or steam. Scope 3: Other indirect emissions, such as the extraction and production of purchased materials and fuels, transport-related activities in vehicles not owned or controlled by the reporting entity, electricity-related activities (e.g. T&D losses) not covered in Scope 2, outsourced activities, waste disposal, etc.
"carbon_dioxide", -- Emissions of the greenhouse gas carbon dioxide (CO2). Units are megatonnes, or one million metric tons.
"sector", -- The broad economic activities that lead to greenhouse gas emissions.
"subsector", -- Narrower, more specific economic activities that lead to greenhouse gas emissions.
"carbon_dioxide_eq", -- Each greenhouse gas contributes differently to global warming. In order to to compare different sources and sectors, greenhouse gas accounting protocols tend to convert greenhouse gases into carbon dioxide equivalent emissions. For example, the most recent Intergovernmental Panel on Climate Change found one metric ton of methane creates 28 times more atmospheric warming than an equal amount of carbon dioxide over a 100 year period. This is known as methane's "global warming potential" (GWP). To convert from methane to CO2e, we multiple a given mass of methane by its GWP of 28. Nitrous oxide has a GWP of 265.
"source" -- The fuel or industrial process that leads to greenhouse gas emissions.
FROM
"cambridgema-gov/cambridge-community-wide-greenhouse-gas-inventory-eiuf-6ksy:latest"."cambridge_community_wide_greenhouse_gas_inventory"
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 cambridgema-gov/cambridge-community-wide-greenhouse-gas-inventory-eiuf-6ksy 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 cambridgema-gov/cambridge-community-wide-greenhouse-gas-inventory-eiuf-6ksy: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 cambridgema-gov/cambridge-community-wide-greenhouse-gas-inventory-eiuf-6ksyCheckout 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 cambridgema-gov/cambridge-community-wide-greenhouse-gas-inventory-eiuf-6ksy:latestThis will download all the objects for the latest tag of cambridgema-gov/cambridge-community-wide-greenhouse-gas-inventory-eiuf-6ksy 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 cambridgema-gov/cambridge-community-wide-greenhouse-gas-inventory-eiuf-6ksy: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 cambridgema-gov/cambridge-community-wide-greenhouse-gas-inventory-eiuf-6ksy: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, cambridgema-gov/cambridge-community-wide-greenhouse-gas-inventory-eiuf-6ksy is just another Postgres schema.