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 work_zone_data_exchange_wzdx_feed_registry table in this repository, by referencing it like:
"datahub-transportation-gov/work-zone-data-exchange-wzdx-feed-registry-69qe-yiui:latest"."work_zone_data_exchange_wzdx_feed_registry"or in a full query, like:
SELECT
":id", -- Socrata column ID
"url", -- URL to the API feed.
"format", -- Format of the data in the API feed. Possible values: xml, json, geojson
":@computed_region_28hd_vqqn",
"version", -- The WZDx version number that the feed follows between the start and end date of the entry.
"issuingorganization", -- Organization issuing and maintaining the work zone data exchange API feed.
":@computed_region_m2nu_4dib",
"lastingestedtosandbox", -- Date and time when the feed was last archived to the ITS WorkZone Data Sandbox, which can be accessed at http://usdot-its-workzone-public-data.s3.amazonaws.com/index.html.
"sdate", -- Start date at which the metadata of the entry (e.g. version number, update frequency, etc) hold true.
"datafeed_frequency_update", -- The frequency at which the data feed is updated and made available through the data feed. Format shall include value + units such as 30s, 15m, or 24h where: s = seconds m = minutes h-hours.
"edate", -- End date at which the metadata of the entry (e.g. version number, update frequency, etc) hold true. If no value is given, the metadata in the entry currently hold true.
"needapikey", -- True if the feed requires the user to create a unique API Key first, URL will direct you to sign up page
"socratadatasetid", -- ID of the relevant sample dataset, if any. You may access the dataset by appending this ID to "https://data.transportation.gov/d/" (e.g., if the dataset ID is "wd94-wugt", it can be accessed at "https://data.transportation.gov/d/wd94-wugt").
"state", -- Lowercase name of the US state where the WZDx feed is from.
"feedname", -- Identifier name of the feed as designated by ITS DataHub when the feed is added to the registry, usually named based on the data providing agency.
"pipedtosandbox", -- Whether or not the feed is actively being archived into the ITS WorkZone Data Sandbox, which can be accessed at http://usdot-its-workzone-public-data.s3.amazonaws.com/index.html.
"active", -- Whether or not the feed is currently active.
"pipedtosocrata", -- Whether or not the feed is actively being sampled into a Socrata dataset on data.transportation.gov.
"apikeyurl", -- The URL for the sign-up page to create an API Key for this data feed
"geocoded_column" -- Coordinate of state column.
FROM
"datahub-transportation-gov/work-zone-data-exchange-wzdx-feed-registry-69qe-yiui:latest"."work_zone_data_exchange_wzdx_feed_registry"
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 datahub-transportation-gov/work-zone-data-exchange-wzdx-feed-registry-69qe-yiui with SQL in under 60 seconds.
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; 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 datahub-transportation-gov/work-zone-data-exchange-wzdx-feed-registry-69qe-yiui: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 datahub-transportation-gov/work-zone-data-exchange-wzdx-feed-registry-69qe-yiuiCheckout 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 datahub-transportation-gov/work-zone-data-exchange-wzdx-feed-registry-69qe-yiui:latestThis will download all the objects for the latest tag of datahub-transportation-gov/work-zone-data-exchange-wzdx-feed-registry-69qe-yiui 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 datahub-transportation-gov/work-zone-data-exchange-wzdx-feed-registry-69qe-yiui: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 datahub-transportation-gov/work-zone-data-exchange-wzdx-feed-registry-69qe-yiui:latestThis 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, datahub-transportation-gov/work-zone-data-exchange-wzdx-feed-registry-69qe-yiui is just another Postgres schema.