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 divvy_bicycle_stations_historical
table in this repository, by referencing it like:
"cityofchicago/divvy-bicycle-stations-historical-eq45-8inv:latest"."divvy_bicycle_stations_historical"
or in a full query, like:
SELECT
":id", -- Socrata column ID
"percent_full", -- Percentage of the docks in service containing an available bike. N/A (denominator is zero) values are indicated by either blank or -1.
"address", -- The street address of the station. This value is not available after 7/7/2019.
"latitude", -- The latitude of the station.
"available_docks", -- Number of docks available to receive a returned bicycle.
"id", -- A unique station identifier. NOTE: Extremely long IDs may not display correctly on this page but should be correct if this dataset is exported or accessed through the API.
"total_docks", -- Total docks in the station. Each dock can accommodate one bicycle.
"longitude", -- The longitude of the station.
"timestamp", -- The date and time the record was recorded.
"station_name", -- The name of the station.
"status", -- The status of the station. Stations "In Service" are available for use.
"available_bikes", -- Number of bicycles available to be rented.
"docks_in_service", -- Excludes docks taken out of service. Calculated as the number of docks reported as containing available bicycles or available to receive returned bicycles.
"record", -- A combination of ID (indicating station) and Timestamp (indicating when the record was recorded) to uniquely identify the record
"location" -- The location of the station in a format that allows for creating maps in this data portal and performing some types of geographic analysis.
FROM
"cityofchicago/divvy-bicycle-stations-historical-eq45-8inv:latest"."divvy_bicycle_stations_historical"
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/divvy-bicycle-stations-historical-eq45-8inv
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/divvy-bicycle-stations-historical-eq45-8inv: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
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; sgr
can 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 clone
and 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/divvy-bicycle-stations-historical-eq45-8inv" \
--handler-options '{
"domain": "data.cityofchicago.org",
"tables": {
"divvy_bicycle_stations_historical": "eq45-8inv"
}
}'
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/divvy-bicycle-stations-historical-eq45-8inv
is just another Postgres schema.