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 crimes_one_year_prior_to_present table in this repository, by referencing it like:
"cityofchicago/crimes-one-year-prior-to-present-x2n5-8w5q:latest"."crimes_one_year_prior_to_present"or in a full query, like:
SELECT
":id", -- Socrata column ID
"arrest", -- Indicates whether an arrest was made.
"_location_description", -- Description of the location where the incident occurred.
"y_coordinate", -- The y coordinate of the location where the incident occurred in State Plane Illinois East NAD 1983 projection. This location is shifted from the actual location for partial redaction but falls on the same block.
"longitude", -- The longitude of the location where the incident occurred. This location is shifted from the actual location for partial redaction but falls on the same block.
"_primary_decsription", -- The primary description of the IUCR code.
"_iucr", -- The Illinois Uniform Crime Reporting Code. This is directly linked to the Primary Type and Description. See the list of IUCR codes at https://data.cityofchicago.org/d/c7ck-438e.
"block", -- The partially redacted address where the incident occurred, placing it on the same block as the actual address.
"case_", -- The Chicago Police Department RD Number (Records Division Number), which is unique to the incident.
"x_coordinate", -- The x coordinate of the location where the incident occurred in State Plane Illinois East NAD 1983 projection. This location is shifted from the actual location for partial redaction but falls on the same block.
"ward", -- The ward (City Council district) where the incident occurred. See the wards at https://data.cityofchicago.org/d/sp34-6z76.
"latitude", -- The latitude of the location where the incident occurred. This location is shifted from the actual location for partial redaction but falls on the same block.
"fbi_cd", -- Indicates the crime classification as outlined in the FBI's National Incident-Based Reporting System (NIBRS). See the Chicago Police Department listing of these classifications at https://gis.chicagopolice.org/pages/crime_details.
"beat", -- Indicates the beat where the incident occurred. A beat is the smallest police geographic area - each beat has a dedicated police beat car. Three to five beats make up a police sector, and three sectors make up a police district. The Chicago Police Department has 22 police districts. See the beats at https://data.cityofchicago.org/d/aerh-rz74.
"domestic", -- Indicates whether the incident was domestic-related as defined by the Illinois Domestic Violence Act.
"date_of_occurrence", -- Date when the incident occurred. This is sometimes a best estimate.
"location", -- The location where the incident occurred in a format that allows for creation of maps and other geographic operations on this data portal. This location is shifted from the actual location for partial redaction but falls on the same block.
"location_city",
"location_zip",
"location_address",
"location_state",
":@computed_region_rpca_8um6",
":@computed_region_43wa_7qmu",
"_secondary_description", -- The secondary description of the IUCR code, a subcategory of the primary description.
":@computed_region_awaf_s7ux",
":@computed_region_6mkv_f3dw",
":@computed_region_vrxf_vc4k",
":@computed_region_bdys_3d7i"
FROM
"cityofchicago/crimes-one-year-prior-to-present-x2n5-8w5q:latest"."crimes_one_year_prior_to_present"
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 cityofchicago/crimes-one-year-prior-to-present-x2n5-8w5q with SQL in under 60 seconds.
This repository is an "external" repository. That means it's hosted elsewhere, in this case at data.cityofchicago.org. When you querycityofchicago/crimes-one-year-prior-to-present-x2n5-8w5q: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.cityofchicago.org, 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 \
"cityofchicago/crimes-one-year-prior-to-present-x2n5-8w5q" \
--handler-options '{
"domain": "data.cityofchicago.org",
"tables": {
"crimes_one_year_prior_to_present": "x2n5-8w5q"
}
}'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, cityofchicago/crimes-one-year-prior-to-present-x2n5-8w5q is just another Postgres schema.