opendata-maryland-gov/chesapeake-bay-pollution-loads-phosphorus-eumn-ip4q
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Query the Data Delivery Network

Query the DDN

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 chesapeake_bay_pollution_loads_phosphorus table in this repository, by referencing it like:

"opendata-maryland-gov/chesapeake-bay-pollution-loads-phosphorus-eumn-ip4q:latest"."chesapeake_bay_pollution_loads_phosphorus"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "total_p_2016_lb", -- total phosphorus for fiscal year 2016 (pounds/year
    "total_p_2015", -- total phosphorus for fiscal year 2015 (pounds/year
    "total_p_2014_lb", -- total phosphorus for fiscal year 2014 (pounds/year
    "_2013", -- total phosphorus for fiscal year 2013 (pounds/year)
    "_2012", -- total phosphorus for fiscal year 2012 (pounds/year)
    "trib_basin", -- tributary basin name
    "county", -- county name
    "land_river_segment",
    "tp_target_2017", -- Maryland phase II watershed implementation plan target loads, fiscal year 2017 (pounds/year).
    "fips", -- FIPS county code
    "major_basin", -- major basin name
    "tp_target_2025", -- Maryland phase II watershed implementation plan final target loads, fiscal year 2025 (pounds/year).
    "_2010", -- total phosphorus for fiscal year 2010 (pounds/year)
    "_1985", -- total phosphorus for fiscal year 1985 (pounds/year)
    "_2009", -- total phosphorus for fiscal year 2009 (pounds/year)
    "_2007", -- total phosphorus for fiscal year 2007 (pounds/year)
    "source_sector", -- source of pollution measured
    "_2011" -- total phosphorus for fiscal year 2011 (pounds/year)
FROM
    "opendata-maryland-gov/chesapeake-bay-pollution-loads-phosphorus-eumn-ip4q:latest"."chesapeake_bay_pollution_loads_phosphorus"
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 opendata-maryland-gov/chesapeake-bay-pollution-loads-phosphorus-eumn-ip4q with SQL in under 60 seconds.

Query Your Local Engine

Install Splitgraph Locally
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 opendata-maryland-gov/chesapeake-bay-pollution-loads-phosphorus-eumn-ip4q: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 opendata-maryland-gov/chesapeake-bay-pollution-loads-phosphorus-eumn-ip4q

Checkout 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 opendata-maryland-gov/chesapeake-bay-pollution-loads-phosphorus-eumn-ip4q:latest

This will download all the objects for the latest tag of opendata-maryland-gov/chesapeake-bay-pollution-loads-phosphorus-eumn-ip4q 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 opendata-maryland-gov/chesapeake-bay-pollution-loads-phosphorus-eumn-ip4q: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 opendata-maryland-gov/chesapeake-bay-pollution-loads-phosphorus-eumn-ip4q:latest

This 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, opendata-maryland-gov/chesapeake-bay-pollution-loads-phosphorus-eumn-ip4q is just another Postgres schema.

Related Documentation:

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