citydata-mesaaz-gov/water-hydrants-r7t3-nh2k
Icon for Socrata external plugin

Query the Data Delivery Network

Query the DDN

The 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
    "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
    "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
    "revision_user", -- UserID of editor who last updated feature
    "hydrant_section", -- Hydrant Section
    "facility_id", -- Unique object ID
    "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
    "depth", -- Depth to nut on Fire Hydrant Valve
    "legacy_id", -- Historic ID of the feature
    "flag_code", -- Extra field used for setting scale in detail boxes
    "document_link", -- Document link, currently not used
    "fire_hydrant_number", -- Fire Hydrant No
    "symbol_scale", -- Symbol scale
    "condition_assessment_date", -- Date of condition assessment
    "city_section", -- City Section; Pulled from WQSRevis feature class
    "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
    "rehab_type", -- Lining material type
    "geolocation", -- The geocoded location of the hydrant
    "user_added", -- UserID of Editor who added feature
    "asset_id", -- Unique Equipment ID
    "fire_hydrant_make", -- Fire Hydrant Make
    "shape", -- Type of object (point, line, polygon, etc.)
    "hydrant_size", -- Barrel size of the hydrant
    "symbol_name", -- Symbol name, once was a required field for EMS Viewer; not sure we still need this field
    "plan_status", -- Status of the source (Permitted, AsBuilt)
    "valve_status", -- Fire Hydrant valve status
    "open_direction", -- Open Direction for Fire Hydrant Valve
    "fire_hydrant_model", -- Fire Hydrant Model
    "city_quarter", -- City Quarter; pulled from WQSRevis feature class
    "service_zone", -- Service zone
    "outlet_size", -- Hydrant outlet size
    "operation_status", -- Operation status; InActive is the default value; after the Letter of Acceptance or Record Drawing is received, this is changed to Active
    "waterhydrant_objectid", -- Unique SDE ID
    "psi", -- Fire Hydrant PSI
    "outlet_size_old", -- Fire Hydrant Outlet Size Old
    "rehab_reference", -- Plan reference for lining project
    "warranty_date", -- Should be warranty date, but field not populated
    "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
    "rehab_year", -- Year lining work was done
    "pipe_size", -- Size of the pipe
    ":@computed_region_fcpr_wj2n"
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.

This repository is an "external" repository. That means it's hosted elsewhere, in this case at citydata.mesaaz.gov. When you querycitydata-mesaaz-gov/water-hydrants-r7t3-nh2k: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

Install Splitgraph Locally
bash -c "$(curl -sL https://github.com/splitgraph/splitgraph/releases/latest/download/install.sh)"
 

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 citydata.mesaaz.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 \
  "citydata-mesaaz-gov/water-hydrants-r7t3-nh2k" \
  --handler-options '{
    "domain": "citydata.mesaaz.gov",
    "tables": {
        "water_hydrants": "r7t3-nh2k"
    }
}'

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, citydata-mesaaz-gov/water-hydrants-r7t3-nh2k is just another Postgres schema.

Related Documentation: