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 total_acres_preserved_in_maryland_counties_by
table in this repository, by referencing it like:
"opendata-maryland-gov/total-acres-preserved-in-maryland-counties-by-tf6f-d4ak:latest"."total_acres_preserved_in_maryland_counties_by"
or in a full query, like:
SELECT
":id", -- Socrata column ID
"total_under_easement", -- TOTAL Under Easement
"next_gen_farmland_acquisition", -- Next Generation Farmland Acquisition Program (MARBIDCO) Easements
"malpf", -- Maryland Agricultural Land Preservation Foundation Easements
"total_publicly_owned", -- TOTAL Publicly Owned
"lpprp_local_parks_and", -- Local Parks and Recreation Land (including Local-Side Program Open Space)
"istea_forest_legacy_crep", -- Intermodal Surface Transportation Efficiency Act (Fed. Scenic Easements), Forest Legacy, Conservation Reserve Enhancement Program, and Farm and Ranch Lands Protection Program-Agricultural Conservation Easement Program Easements
"pos_stateside_conservation", -- Maryland Program Open Space Stateside Conservation Easements
"private_cons_orgs", -- Land/Easements Held by Private Conservation Organizations
"jurisdiction_code", -- MdProperty View Jurisdiction Code (Four-letter County or Baltimore City code)
"maryland_county", -- Maryland County
"maryland_region", -- Maryland Region
"lpprp_federal_park_and", -- Federal Park and Conservation Lands
"dnr_state_land_inventory", -- Maryland Department of Natural Resources State Land Inventory
"met", -- Maryland Environmental Trust Easements
"cluster_subdv_remainder", -- County Protected Cluster/Subdivision Remainders
"county_pdr_tdr", -- County Purchase of Development Rights/Transfer of Development Rights Easements
"best_available_data_as_of", -- Data are not provided real-time but do represent the best available data as of this date
"grand_total_preserved", -- GRAND TOTAL Preserved
"rural_legacy" -- Maryland Rural Legacy Program Easements
FROM
"opendata-maryland-gov/total-acres-preserved-in-maryland-counties-by-tf6f-d4ak:latest"."total_acres_preserved_in_maryland_counties_by"
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 opendata-maryland-gov/total-acres-preserved-in-maryland-counties-by-tf6f-d4ak
with SQL in under 60 seconds.
This repository is an "external" repository. That means it's hosted elsewhere, in this case at opendata.maryland.gov. When you queryopendata-maryland-gov/total-acres-preserved-in-maryland-counties-by-tf6f-d4ak: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; sgr
can 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 clone
and sgr checkout
.
Mounting Data
This repository is an external repository. It's not hosted by Splitgraph. It is hosted by opendata.maryland.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 \
"opendata-maryland-gov/total-acres-preserved-in-maryland-counties-by-tf6f-d4ak" \
--handler-options '{
"domain": "opendata.maryland.gov",
"tables": {
"total_acres_preserved_in_maryland_counties_by": "tf6f-d4ak"
}
}'
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, opendata-maryland-gov/total-acres-preserved-in-maryland-counties-by-tf6f-d4ak
is just another Postgres schema.