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 water_hydrants table in this repository, by referencing it like:
"citydata-mesaaz-gov/water-hydrants-r7t3-nh2k:latest"."water_hydrants"or in a full query, like:
SELECT
":id", -- Socrata column ID
"depth", -- Depth to nut on Fire Hydrant Valve
"warranty_date", -- Should be warranty date, but field not populated
"outlet_size", -- Hydrant outlet size
"condition_of_asset", -- Numeric value assigned to some features reflecting the condition of the asset
"owner_id", -- Who owns the feature
"maintenance_year", -- Year maintenance was performed
"fire_hydrant_number", -- Fire Hydrant No
"rehab_year", -- Year lining work was done
"document_link", -- Document link, currently not used
"flag_code", -- Extra field used for setting scale in detail boxes
"water_hydrant_id", -- Foreign Key for joining to FacilityID in WHydrant table
"valve_turns", -- Fire Hydrant valve turns
"valve_location", -- Fire Hydrant valve location ties
"pipe_size", -- Size of the pipe
":@computed_region_fcpr_wj2n",
"legacy_id", -- Historic ID of the feature
"rehab_type", -- Lining material type
"hydrant_size", -- Barrel size of the hydrant
"service_zone", -- Service zone
"city_quarter", -- City Quarter; pulled from WQSRevis feature class
"geolocation", -- The geocoded location of the hydrant
"user_added", -- UserID of Editor who added feature
"asset_id", -- Unique Equipment ID
"tag", -- Concatenated values from Hydrant Section AND Hydrant Number
"revision_date", -- Date feature was last updated in GIS
"remarks", -- General information about equipment not captured elsewhere
"install_date", -- Date of installation
"full_address", -- Full Address
"class", -- Identifies standard vs non-standard hydrants
"asb_year", -- Year feature record drawing was completed
"date_added", -- Date feature was added to GIS
"symbol_rotation", -- Symbol rotation
"location", -- Street name the feature is situated in
"fire_hydrant_make", -- Fire Hydrant Make
"rehab_reference", -- Plan reference for lining project
"ancillary_role", -- Source or Sink
"longitude", -- Longitude of water hydrant or maintenance performed
"subtype", -- Feature type
"maintenance_date", -- Fire Hydrant Maintenance Date
"comments", -- General information about a feature not captured elsewhere
"outlet_size_old", -- Fire Hydrant Outlet Size Old
"city_section", -- City Section; Pulled from WQSRevis feature class
"revision_user", -- UserID of editor who last updated feature
"psi", -- Fire Hydrant PSI
"shape", -- Type of object (point, line, polygon, etc.)
"fire_hydrant_model", -- Fire Hydrant Model
"hydrant_section", -- Hydrant Section
"open_direction", -- Open Direction for Fire Hydrant Valve
"condition_assessment_date", -- Date of condition assessment
"valve_status", -- Fire Hydrant valve status
"facility_id", -- Unique object ID
"plan_status", -- Status of the source (Permitted, AsBuilt)
"symbol_name", -- Symbol name, once was a required field for EMS Viewer; not sure we still need this field
"waterhydrant_objectid", -- Unique SDE ID
"operation_status", -- Operation status; InActive is the default value; after the Letter of Acceptance or Record Drawing is received, this is changed to Active
"maintenance_month_date", -- Date maintenance was performed
"maintenance_month", -- Month maintenance was performed
"valve_make", -- Fire Hydrant valve make
"waterhydrantproperty_objectid", -- Unique SDE ID in Water Hydrant Property Table
"hydrant_number", -- Hydrant Number
"enabled", -- Identifies features that are included in the network
"latitude", -- Latitude of water hydrant or maintenance performed
"plan_reference", -- Source reference number
"symbol_scale" -- Symbol scale
FROM
"citydata-mesaaz-gov/water-hydrants-r7t3-nh2k:latest"."water_hydrants"
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 citydata-mesaaz-gov/water-hydrants-r7t3-nh2k 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 citydata-mesaaz-gov/water-hydrants-r7t3-nh2k: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 citydata-mesaaz-gov/water-hydrants-r7t3-nh2kCheckout 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 citydata-mesaaz-gov/water-hydrants-r7t3-nh2k:latestThis will download all the objects for the latest tag of citydata-mesaaz-gov/water-hydrants-r7t3-nh2k 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 citydata-mesaaz-gov/water-hydrants-r7t3-nh2k: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 citydata-mesaaz-gov/water-hydrants-r7t3-nh2k: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, citydata-mesaaz-gov/water-hydrants-r7t3-nh2k is just another Postgres schema.