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 tree_removal_permits table in this repository, by referencing it like:
"cambridgema-gov/tree-removal-permits-vj95-me7d:latest"."tree_removal_permits"or in a full query, like:
SELECT
":id", -- Socrata column ID
"fulladdress", -- Address where tree is located
"company_name", -- Company responsible for removing tree.
"exceptional", -- Exceptional Tree. Any Significant Tree thirty (30) inches DBH or larger which is on a Lot.
"issue_date", -- Issue date for permit application.
"submit_date", -- Submission date for permit application.
"city_property", -- Tree is located on city property
"replacement_tree", -- A tree or trees to be planted to replace any Significant Trees to be removed
"prior_removal", -- Has tree been removed prior to permit obtainment
"id", -- Permit ID
"planning_board", -- Is this application subject to a special planning board permit?
"large_project", -- The tree removal constitutes or is part of a large project under relevant ordinances.
"reason_description", -- Details of reason
"points_for_mapping", -- Coordinates formatted for mapping trees within the Socrata open data portal's built in map generator.
"height", -- Height of trees
"diameter_six_inch", -- The tree meets or exceeds a diameter of six inches at breast height (DBH)
"latitude", -- Latitude where tree is located
"longitude", -- Longitude where tree is located
"location", -- Location of tree on lot
"replacements", -- Number of replacements
"mitigation_fee", -- Mitigation fee paid for removal.
"reason", -- Reason for removal
"species", -- Tree species
"mitigation_plan", -- Plan to mitigate losses from tree removal
"status", -- Status of tree removal permit.
":@computed_region_guic_hr4a", -- This column was automatically created in order to record in what polygon from the dataset 'Police Neighborhood Regions' (guic-hr4a) the point in column 'points_for_mapping' is located. This enables the creation of region maps (choropleths) in the visualization canvas and data lens.
":@computed_region_v7jj_366k", -- This column was automatically created in order to record in what polygon from the dataset 'Police Response Districts' (v7jj-366k) the point in column 'points_for_mapping' is located. This enables the creation of region maps (choropleths) in the visualization canvas and data lens.
":@computed_region_rffn_qbt6", -- This column was automatically created in order to record in what polygon from the dataset 'cambridge_neighborhoods' (rffn-qbt6) the point in column 'points_for_mapping' is located. This enables the creation of region maps (choropleths) in the visualization canvas and data lens.
":@computed_region_swkg_bavi", -- This column was automatically created in order to record in what polygon from the dataset 'cambridge_cdd_zoning' (swkg-bavi) the point in column 'points_for_mapping' is located. This enables the creation of region maps (choropleths) in the visualization canvas and data lens.
":@computed_region_e4yd_rwk4", -- This column was automatically created in order to record in what polygon from the dataset 'Census Blocks 2010' (e4yd-rwk4) the point in column 'points_for_mapping' is located. This enables the creation of region maps (choropleths) in the visualization canvas and data lens.
"special_circumstances", -- Special circumstances surrounding the tree removal.
"diameter", -- Diameter at breast height (DBH) of the tree
"dead_or_dangerous", -- Tree is dead or dangerous
"number", -- Number of trees removed
"street" -- Street where tree is located.
FROM
"cambridgema-gov/tree-removal-permits-vj95-me7d:latest"."tree_removal_permits"
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/tree-removal-permits-vj95-me7d with SQL in under 60 seconds.
This repository is an "external" repository. That means it's hosted elsewhere, in this case at data.cambridgema.gov. When you querycambridgema-gov/tree-removal-permits-vj95-me7d: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.cambridgema.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 \
"cambridgema-gov/tree-removal-permits-vj95-me7d" \
--handler-options '{
"domain": "data.cambridgema.gov",
"tables": {
"tree_removal_permits": "vj95-me7d"
}
}'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, cambridgema-gov/tree-removal-permits-vj95-me7d is just another Postgres schema.