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 real_property_tax_rates table in this repository, by referencing it like:
"montgomerycountymd-gov/real-property-tax-rates-es5m-4wf9:latest"."real_property_tax_rates"or in a full query, like:
SELECT
":id", -- Socrata column ID
"total_tax_rate",
"municipal_district_tax", -- Municipal District Property Tax is levied by each municipal area and generally funds street and sidewalk maintenance, trash removal, tree care, sanitation, and police protection.
"general_county_tax", -- The General County tax is levied on all property in the County and funds, in part, such basic services as police protection, elementary and secondary education, the community college, transportation, health and social services, and libraries.
"total_special_service_area_tax", -- The Special Service Area Tax includes Transit, Fire District, Advanced Land Acquisition, Metropolitan, Regional, Recreation, Storm Drainage, Parking Lot District, Urban District, Noise Abatement District, and Development District taxes.
"development_district_tax", -- Development District and Special Taxing District Tax is levied to finance certain infrastructure improvements through secured bond issuance. Revenues collected are used exclusively for the applicable district.
"noise_abatement_district_tax", -- Noise Abatement Tax funds noise abatement district improvements. Whether a taxpayer pays one of these special area taxes depends on where the property is located.
"urban_district_tax", -- Urban District Tax funds urban district improvements. Whether a taxpayer pays one of these special area taxes depends on where the property is located.
"parking_lot_district_tax", -- Parking Lot District Tax funds parking lot districts improvements. Whether a taxpayer pays one of these special area taxes depends on where the property is located.
"storm_drainage_tax", -- Storm Drainage Tax funds storm drainage improvements. Whether a taxpayer pays one of these special area taxes depends on where the property is located.
"transit_tax", -- Transit Tax is levied Countywide and funds public transportation services including the Ride On bus system.
"advanced_land_acquisition_tax", -- Advance Land Acquisition Tax is levied Countywide and funds land acquisitions by the Maryland-National Capital Park and Planning Commission (M-NCPPC).
"regional_tax", -- Regional Tax funds M-NCPPC planning and administrative programs. Whether a taxpayer pays one of these special area taxes depends on where the property is located.
"metro_politan_tax", -- Metropolitan Tax funds M-NCPPC local park facilities and parks programs. Whether a taxpayer pays one of these special area taxes depends on where the property is located.
"recreation_tax", -- Recreation tax funds recreation facilities and programs. Whether a taxpayer pays one of these special area taxes depends on where the property is located.
"tax_class",
"state_tax", -- This tax is levied by the State of Maryland for the payment of principal and interest on State bonds.
"fire_district_tax" -- Fire District Tax is levied Countywide and funds fire and rescue services.
FROM
"montgomerycountymd-gov/real-property-tax-rates-es5m-4wf9:latest"."real_property_tax_rates"
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 montgomerycountymd-gov/real-property-tax-rates-es5m-4wf9 with SQL in under 60 seconds.
This repository is an "external" repository. That means it's hosted elsewhere, in this case at data.montgomerycountymd.gov. When you querymontgomerycountymd-gov/real-property-tax-rates-es5m-4wf9: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; sgrcan 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 cloneand sgr checkout.
Mounting Data
This repository is an external repository. It's not hosted by Splitgraph. It is hosted by data.montgomerycountymd.gov, 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 \
"montgomerycountymd-gov/real-property-tax-rates-es5m-4wf9" \
--handler-options '{
"domain": "data.montgomerycountymd.gov",
"tables": {
"real_property_tax_rates": "es5m-4wf9"
}
}'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, montgomerycountymd-gov/real-property-tax-rates-es5m-4wf9 is just another Postgres schema.