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 public_trees table in this repository, by referencing it like:
"calgary-ca/public-trees-tfs4-3wwa:latest"."public_trees"or in a full query, like:
SELECT
":id", -- Socrata column ID
":@computed_region_qeuu_piif",
":@computed_region_kxmf_bzkv",
"point",
"modified_dt",
"active_dt",
"hardware",
"site_element_minortype",
"site_element_type_description",
"location_detail",
"comm_code", -- The short-hand code used to identify the community an asset resides in.
"wam_id", -- The unique identifier used to identify Parks assets. Each tree has its own WAM_ID.
"maintained_by", -- The organization currently responsible for maintenance of the asset.
"tree_maintenance", -- The current general maintenance level provided to the tree based up tree stage of life. ESTABLISH TREE – A young tree that needs help to get established and generally receives watering and higher maintenance; MAINTAIN TREE – An established, mature tree that only receives maintenance as needed; MAINTAIN SHRUB – Shrub that will only receive maintenance as needed; PLANT SITE – After a tree and its stump are removed, this indicates it may be a good spot to plant a new tree; STUMP REMOVAL – The tree has been removed, and a stump remains which requires removal.
"heritage_trees", -- A tree determined to be a Heritage Tree.
"tree_condition_rating_perc", -- The most recent condition of a tree given as a percentage, which is determined by trained Urban Forestry staff during their last visit to that tree.
"appraised_value",
"rating", -- The rating of the tree species based on the Alberta Tree Species Rating Guide from the ISA (International Society of Arboriculture).
"mature_size", -- The expected size of a tree at full maturity.
"dbh_cm", -- The diameter at breast height (approximately 1.4 m) of a tree in centimeters.
"cultivar", -- The cultivar name of the tree.
"species", -- The second part in the binomial species name of a tree.
"genus", -- The first part in the binomial species name of a tree.
"hort_code", -- The short-hand code used by The City of Calgary to identify genus, species and cultivar.
"common_name", -- The non-scientific name given for a tree.
"asset_subtype", -- Deciduous trees will change colour and lose leaves in the fall, while Evergreen (Coniferous) trees will retain their needles throughout the winter.
"asset_type", -- The type of Parks asset
"tree_asset_cd" -- The short-hand code used to identify the community and park number an asset resides in.
FROM
"calgary-ca/public-trees-tfs4-3wwa:latest"."public_trees"
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 calgary-ca/public-trees-tfs4-3wwa 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 calgary-ca/public-trees-tfs4-3wwa: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 calgary-ca/public-trees-tfs4-3wwaCheckout 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 calgary-ca/public-trees-tfs4-3wwa:latestThis will download all the objects for the latest tag of calgary-ca/public-trees-tfs4-3wwa 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 calgary-ca/public-trees-tfs4-3wwa: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 calgary-ca/public-trees-tfs4-3wwa: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, calgary-ca/public-trees-tfs4-3wwa is just another Postgres schema.