cambridgema-gov/citywide-bicycle-counts-ijm6-q7em
Icon for Socrata external plugin

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 citywide_bicycle_counts table in this repository, by referencing it like:

"cambridgema-gov/citywide-bicycle-counts-ijm6-q7em:latest"."citywide_bicycle_counts"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "cyclistlocation", -- The location of the cyclist may be: Street (travelling in the street or bike lane), Sidewalk (riding on the sidewalk), or Bikepath
    "movementtype", -- The specific movement made by the cyclists in this count, for example Left, Right, or Thru. Values vary by count location. "Red Light Running" indicates cyclists that ran the red light. Counts with these values are independent of the turnning movement - a cyclist running a red light to turn left would also be recorded under a "Left" turning movement for this location and time.
    "countlocation", -- The assigned name for the count location. Where possible, this is the name used in the Cambridge GIS Intersections layer
    "year", -- The year the count occurred
    "date", -- The date the count occurred
    "time", -- The start of the 15-minute interval represented in the count record
    "street", -- The street where the count occurred
    "count", -- The count of cyclists for this 15-minute period reflecting the associated location, year, time, street, traffic direction, cyclist location, cyclist direction, and movement type.
    "temperature", -- If the time period is AM, the temperature in Fahrenheit degrees at 8:00 AM on the count date. If the time period is PM, the temperature at 5:00 pm on the count date.
    "weather", -- If the time period is AM, a description of the weather at 8:00 AM on the count date. If the time period is PM, a description of the weather at  5:00 pm on the count date.
    "notes", -- Notes related to this count record. May note that the count occurred outside of the typical September count period, or that there was construction in the area during the count.
    "nodenumber", -- The NodeNumber corresponding to the count location from the City GIS Intersections layer, if available.
    "latitude", -- The latitude of the count location
    "longitude", -- The longitude of the count location
    "timeperiod", -- Identifies morning (AM) and evening (PM) count periods
    "cyclistdirection", -- The direction of the cyclist in relation to the legal traffic direction. May be With Traffic, Against Traffic, or Bikepath
    "trafficdirection" -- The legal direction of traffic on the street where the count occurred
FROM
    "cambridgema-gov/citywide-bicycle-counts-ijm6-q7em:latest"."citywide_bicycle_counts"
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/citywide-bicycle-counts-ijm6-q7em with SQL in under 60 seconds.

This repository is an "external" repository. That means it's hosted elsewhere, in this case at data.cambridgema.gov. When you querycambridgema-gov/citywide-bicycle-counts-ijm6-q7em:latest on the DDN, we "mount" the repository using the socrata mount handler. The mount handler proxies your SQL query to the upstream data source, translating it from SQL to the relevant language (in this case SoQL).

We also cache query responses on the DDN, but we run the DDN on multiple nodes so a CACHE_HIT is only guaranteed for subsequent queries that land on the same node.

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 (like this repository), 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, where the author has pushed Splitgraph Images to the repository, you can "clone" and/or "checkout" the data using sgr cloneand sgr checkout.

Mounting Data

This repository is an external repository. It's not hosted by Splitgraph. It is hosted by data.cambridgema.gov, and Splitgraph indexes it. This means it is not an actual Splitgraph image, so you cannot use sgr clone to get the data. Instead, you can use the socrata adapter with the sgr mount command. Then, if you want, you can import the data and turn it into a Splitgraph image that others can clone.

First, install Splitgraph if you haven't already.

Mount the table with sgr mount

sgr mount socrata \
  "cambridgema-gov/citywide-bicycle-counts-ijm6-q7em" \
  --handler-options '{
    "domain": "data.cambridgema.gov",
    "tables": {
        "citywide_bicycle_counts": "ijm6-q7em"
    }
}'

That's it! Now you can query the data in the mounted table like any other Postgres table.

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/citywide-bicycle-counts-ijm6-q7em is just another Postgres schema.