cityofnewyork-us/air-quality-c3uy-2p5r
Loading...
  •  
    Overview
  •  
    Tables
  • Loading...
  •  
    REST API
  • Loading...
  •  
    SQL Query

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 air_quality table in this repository, by referencing it like:

"cityofnewyork-us/air-quality-c3uy-2p5r:latest"."air_quality"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "message", -- notes that apply to the data value; For example, if an estimate is based on small numbers we will detail here
    "start_date", -- Date value for the start of the time_period; Always a date value; could be useful for plotting a time series
    "geo_join_id", -- Identifier of the neighborhood geographic area, used for joining to mapping geography files to make thematic maps
    "data_value", -- The actual data value for this indicator, measure, place, and time
    "measure_info", -- Information (such as units) about the measure
    "unique_id", -- Unique record identifier
    "indicator_id", -- Identifier of the type of measured value across time and space
    "name", -- Name of the indicator
    "measure", -- How the indicator is measured
    "geo_type_name", -- Geography type; UHF' stands for United Hospital Fund neighborhoods; For instance, Citywide, Borough, and Community Districts are different geography types
    "geo_place_name", -- Neighborhood name
    "time_period" -- Description of the time that the data applies to ; Could be a year, range of years, or season for example
FROM
    "cityofnewyork-us/air-quality-c3uy-2p5r:latest"."air_quality"
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 cityofnewyork-us/air-quality-c3uy-2p5r 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 cityofnewyork-us/air-quality-c3uy-2p5r: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 cityofnewyork-us/air-quality-c3uy-2p5r

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 cityofnewyork-us/air-quality-c3uy-2p5r:latest

This will download all the objects for the latest tag of cityofnewyork-us/air-quality-c3uy-2p5r 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 cityofnewyork-us/air-quality-c3uy-2p5r: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 cityofnewyork-us/air-quality-c3uy-2p5r: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, cityofnewyork-us/air-quality-c3uy-2p5r is just another Postgres schema.

Related Documentation:

Loading...