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 transit_agency_security_personnel table in this repository, by referencing it like:
"datahub-transportation-gov/transit-agency-security-personnel-hswt-qvr8:latest"."transit_agency_security_personnel"or in a full query, like:
SELECT
":id", -- Socrata column ID
"contractedsecurityforcefl", -- If True, the agency retains secondary personnel who are: Contracted non-sworn security guards (i.e., not sworn police officers).
"ntdid", -- A five-digit ID representing the unique entity reporting Safety and Security data to the National Transit Database.
"reportyear", -- The calendar year at the beginning of which Security Personnel staffing levels were measured.
"secondarypersonnelcnt", -- Count of all secondary personnel, which are security forces are those who occasionally respond to events occurring on transit property or those who assist the primary force.
"useoflocalpolicenoncontr", -- If True, the agency retains secondary personnel who are:Local police or a sheriff’s department provides security for a transit agency. An agency would select this option if it does not pay for this coverage through a contractual arrangement. The local police or sheriff’s department includes transportation in its general policing activities.
"dedicatedtransitpolicefl", -- If True the agency retains secondary personnel who are: A (sworn) police force that works only for the transit agency.
"totalpersonnelcnt", -- Sum of Primary and Secondary security personnel. Note - if an agency has a dedicated transit police force that responds to events across two modes, but one of those modes never requires a security response, the agency may report zero (0) security personnel for that mode.
"typeofservicecd", -- An abbreviation of the type of service provided. For a key, see the Introduction section of the most recently published NTD Safety and Security reporting manual on this page: https://www.transit.dot.gov/ntd/manuals
"primarysecuritytypecnt", -- A sum of all personnel who routinely patrol the transit property.
"primarysecuritytypedesc", -- (Required) Classification of personnel who routinely patrol or respond to events on transit property.
"dedicatedlocalpolicefl", -- If True the agency retains secondary personnel who are: A municipal police force or sheriff’s department (not paid for directly by your agency) that has a specific transit unit or department.
"modecd", -- An abbreviation of the mode of service provided. For a key, see the Introduction section of the most recently published NTD Safety and Security reporting manual on this page: https://www.transit.dot.gov/ntd/manuals
"reportername", -- The name of the entity reporting the given record.
"transitagencysecurityforcefl", -- If True, the agency retains secondary personnel who are: In-house, non-sworn security guards (i.e., not sworn police officers). In this case, the security guards are employees of the transit agency. Contracted security force: Cont
"offdutypoliceofficersfl", -- If True, the agency retains secondary personnel who are:Off-duty police officers who “moonlight” at a transit agency (e.g., the agency contracts directly with individual off-duty officers as opposed to contracting with a private company that may be staffed by a combination of off-duty police officers and other personnel).
"contractedlocallawenforc" -- If True the agency retains secondary personnel who are: A local police department or sheriff’s department that is contracted by a transit agency to provide security services.
FROM
"datahub-transportation-gov/transit-agency-security-personnel-hswt-qvr8:latest"."transit_agency_security_personnel"
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/transit-agency-security-personnel-hswt-qvr8 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/transit-agency-security-personnel-hswt-qvr8: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/transit-agency-security-personnel-hswt-qvr8Checkout 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/transit-agency-security-personnel-hswt-qvr8:latestThis will download all the objects for the latest tag of datahub-transportation-gov/transit-agency-security-personnel-hswt-qvr8 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/transit-agency-security-personnel-hswt-qvr8: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/transit-agency-security-personnel-hswt-qvr8: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/transit-agency-security-personnel-hswt-qvr8 is just another Postgres schema.