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 computer_aided_dispatch_entries_2015_deprecated table in this repository, by referencing it like:
"cambridgema-gov/computer-aided-dispatch-entries-2015-deprecated-akku-y4tf:latest"."computer_aided_dispatch_entries_2015_deprecated"or in a full query, like:
SELECT
":id", -- Socrata column ID
"neighborhoodid", -- Code for Neighborhood district
"group", -- General crime/fire grouping
"firebox", -- The Fire Department divides the city into "Firebox" districts, each assigned a unique response pre-plan.
"datetimeclosed", -- Time event no longer active in CAD system. Might include subsequent administrative or investigative period.
"neighborhood", -- Name of Neighborhood district
"policesector", -- The Police Department divides the city into 5 "sectors", for events requiring a two person response.
"priority", -- 1=Most critical, 2=medium, 3=least critical event
"reportingarea", -- The smallest geographic polygon used to determine which units are assigned to an area. Usually about the size of a city block.
"type", -- Initial event as categorized by 911 call taker
"intersection", -- The cross streets where an event happened, usually traffic-related.
"fygroup", -- Grouping for Emergency Communications Dept. annual report summary totals
"datetimereceived", -- Time when entered into CAD system. Does not always reflect actual time of event.
"_1xxaddress", -- Nearest address to event. Address with 100's block house numbers.
"primaryagency", -- P=Police, F=Fire
"ladderdistrict", -- The Fire Department divides the city into 4 Ladder Districts, one for each of the on duty Ladder companies.
"enginedistrict", -- The Fire Department divides the city into 8 Engine Districts, one for each of the on duty Engine companies.
"policeroute", -- The Police Department divides the city into 9 "routes", for events requiring a single person response.
"alarmlevel" -- Fire events only. Number of "Fire Alarms". The higher the number, the greater the number of responding apparatus.
FROM
"cambridgema-gov/computer-aided-dispatch-entries-2015-deprecated-akku-y4tf:latest"."computer_aided_dispatch_entries_2015_deprecated"
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/computer-aided-dispatch-entries-2015-deprecated-akku-y4tf 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 cambridgema-gov/computer-aided-dispatch-entries-2015-deprecated-akku-y4tf: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 cambridgema-gov/computer-aided-dispatch-entries-2015-deprecated-akku-y4tfCheckout 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 cambridgema-gov/computer-aided-dispatch-entries-2015-deprecated-akku-y4tf:latestThis will download all the objects for the latest tag of cambridgema-gov/computer-aided-dispatch-entries-2015-deprecated-akku-y4tf 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 cambridgema-gov/computer-aided-dispatch-entries-2015-deprecated-akku-y4tf: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 cambridgema-gov/computer-aided-dispatch-entries-2015-deprecated-akku-y4tf: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, cambridgema-gov/computer-aided-dispatch-entries-2015-deprecated-akku-y4tf is just another Postgres schema.