cityofchicago/parking-permit-zones-u9xt-hiju
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 parking_permit_zones table in this repository, by referencing it like:

"cityofchicago/parking-permit-zones-u9xt-hiju:latest"."parking_permit_zones"

or in a full query, like:

SELECT
    ":id", -- Socrata column ID
    "street_direction",
    "row_id", -- Unique ID
    "street_name",
    "address_range_low", -- Lower value in the address range
    "address_range_high", -- Higher value in the address range
    "odd_even", -- If 'E', only products whose address is both within this range AND address is even numbered will be offered zone.   If 'O', only products whose address is both within this range AND address is odd numbered will be offered zone.
    "ward_low", -- The ward in which the low end of the address range falls.
    "zone", -- The zone number.  In cases where signs are posted (i.e., range is not a buffer range), this is the number that is listed on the physical sign.
    "ward_high", -- The ward in which the high end of the address range falls.
    "status", -- ACTIVE = currently affects product issuance (i.e., zoned products offered if product's address is within this zone record's range) RESCINDED = does not affect product issuance.  The street range indicated by this record previously existed (i.e., signs used to be in the ground, or the range used to be a buffer), but between such time and present, the zone has been cancelled (with signs removed, etc.) pursant to City Council legislation or similar act. 
    "buffer", -- Some segments are "Buffer": Parking is not restricted on the physical street, but residents who reside at an address within that range shall be eligible to purchase zoned products for nearby "Standard" segments where parking is restricted and signs are physically posted on the street.  Y = The range is a buffer segment.   N = The range is not a buffer segment, i.e., is a "standard" segment.
    "second_street_direction",
    "street_type"
FROM
    "cityofchicago/parking-permit-zones-u9xt-hiju:latest"."parking_permit_zones"
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 cityofchicago/parking-permit-zones-u9xt-hiju with SQL in under 60 seconds.

This repository is an "external" repository. That means it's hosted elsewhere, in this case at data.cityofchicago.org. When you querycityofchicago/parking-permit-zones-u9xt-hiju: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)"
 

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.cityofchicago.org, 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 \
  "cityofchicago/parking-permit-zones-u9xt-hiju" \
  --handler-options '{
    "domain": "data.cityofchicago.org",
    "tables": {
        "parking_permit_zones": "u9xt-hiju"
    }
}'

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, cityofchicago/parking-permit-zones-u9xt-hiju is just another Postgres schema.

Related Documentation: