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_art table in this repository, by referencing it like:
"cambridgema-gov/public-art-p4zn-aid4:latest"."public_art"or in a full query, like:
SELECT
":id", -- Socrata column ID
"merge_numb", -- Unique ID number
"photo_webs", -- link to a picture of the art
"tour_card", -- Cambridge Arts Public Art Tour in which the artwork is included, when applicable.
"tag_keywor", -- additional themes
"actual_add", -- Street address of art location, when applicable.
"dimensions", -- Measurements of height, width and depth for the art.
"last_name", -- artist last name
"art_year", -- year the art was completed
"website_ca", -- Art category. Can be one of six types, sculpture, mosaic, mural, stained glass, landscape or electronic.
"series", -- Name of the series in which the art is included.
"zoom", -- Describes what zoom level the point should be visible at. Out points should only be seen from farther away, and in points should only be seen from close up.
"nearest_po",
"tour_card_", -- Cambridge Arts Public Art Tour in which the artwork is included, when applicable.
"list_title", -- list title
"tags_keywo", -- Main theme of the artwork.
"photo_capt", -- photo caption
"additional", -- Details describing the art location.
"location", -- name of art location
"object_typ", -- Descriptors of the type of art object.
"more_info_",
"last_edite",
"created_da",
"latitude",
"google_map", -- map URL
"video_url", -- video URL
"major_cons", -- Year of the last major conservation treatment of the art.
"interior_e", -- Location of the art. Either Interior or Exterior.
"photo_qual",
"display_te", -- Year until which art will be displayed if temporary.
"photo_alt_", -- photo alternative text
"fact_sheet", -- fact sheet URL
"permissi_1", -- How to receive permission to view art.
"current_in",
"temporary_", -- Indicates whether the art is part of Cambridge's permanent collection
"permission", -- Whether or not permission is required to view the artwork.
"related_pr",
"neighborho", -- Neighborhood in Cambridge in which art is located.
"location_1", -- Additional descriptors for the type of location where the art is located.
"detailed_m", -- Materials used to build/ construct the art.
"title", -- Title given to the piece of art.
"first_name", -- artist first name
"accession_", -- Cambridge Arts collection number assigned to the art.
"longitude",
"artist_ful", -- Artist's full name
"the_geom", -- Geospatial layer geometry. The latitude and longitude data for the underlying map shapes.
"location_t", -- Main descriptor of where the art is located.
"conservati", -- Indicates whether or not a piece is on display due to Conservation work
"special_in",
"short_desc", -- description of art
":@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 'the_geom' 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 'the_geom' 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 'the_geom' 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 'the_geom' is located. This enables the creation of region maps (choropleths) in the visualization canvas and data lens.
":@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 'the_geom' is located. This enables the creation of region maps (choropleths) in the visualization canvas and data lens.
"featured" -- Whether or not art is featured on the Cambridge Arts digital map.
FROM
"cambridgema-gov/public-art-p4zn-aid4:latest"."public_art"
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/public-art-p4zn-aid4 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 cambridgema-gov/public-art-p4zn-aid4: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 cambridgema-gov/public-art-p4zn-aid4Checkout 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 cambridgema-gov/public-art-p4zn-aid4:latestThis will download all the objects for the latest tag of cambridgema-gov/public-art-p4zn-aid4 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 cambridgema-gov/public-art-p4zn-aid4: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 cambridgema-gov/public-art-p4zn-aid4: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, cambridgema-gov/public-art-p4zn-aid4 is just another Postgres schema.