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 traffic_links_stats table in this repository, by referencing it like:
"data-act-gov-au/traffic-links-stats-jn4p-azhb:latest"."traffic_links_stats"or in a full query, like:
SELECT
":id", -- Socrata column ID
"trend", -- The last hour of link travel time values in seconds based on 5-minute intervals
"speed", -- The current link average travel speed in kilmetres per hour
"direction", -- A descriptive name for the link’s general direction of travel
"destsiteid", -- The unique Addinsight site Id for the destination site (end of the link)
"tt", -- The current link travel time in seconds
"congestion", -- The current link excess delay converted into a number of standard deviations. This is an alternative unusual congestion indicator to excess delay
"id", -- The Addinsight unique identifier for the link
"mintt", -- The system-calculated freeflow travel time in seconds based on actual data collected in non-congested conditions
"length", -- The length of the link in metres
"excessdelay", -- The current link delay in seconds compared to the travel time expected for this time of day and day of the week. Best described as unusual or unexpected delay
"delay", -- The current link delay in seconds (TT - MinTT)
"name", -- A descriptive name for the link
"intervalstart", -- The start log time for the live statistics provided in the properties below
"score", -- A value from 0-7 to highlight links that have unusual congestion (0 is normal and 7 is bad). Uses the excess delay and congestion values to determine the score using the link_scores.json values
"originsiteid", -- The unique Addinsight site Id for the origin site (start of the link)
"isfreeway", -- Defines whether the link is a signalised or freeway corridor
"closed", -- A link can be manually marked as closed if there is a restriction preventing traffic to travel along the link
"enoughdata", -- Whether the data recently collected meets the system thresholds for being statistically reliable
"minnumberoflanes", -- The minimum number of lanes along the link
"line"
FROM
"data-act-gov-au/traffic-links-stats-jn4p-azhb:latest"."traffic_links_stats"
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 data-act-gov-au/traffic-links-stats-jn4p-azhb 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 data-act-gov-au/traffic-links-stats-jn4p-azhb: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 data-act-gov-au/traffic-links-stats-jn4p-azhbCheckout 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 data-act-gov-au/traffic-links-stats-jn4p-azhb:latestThis will download all the objects for the latest tag of data-act-gov-au/traffic-links-stats-jn4p-azhb 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 data-act-gov-au/traffic-links-stats-jn4p-azhb: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 data-act-gov-au/traffic-links-stats-jn4p-azhb: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, data-act-gov-au/traffic-links-stats-jn4p-azhb is just another Postgres schema.