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 development_log_historical_projects_use_data_1997 table in this repository, by referencing it like:
"cambridgema-gov/development-log-historical-projects-use-data-1997-r5mv-isth:latest"."development_log_historical_projects_use_data_1997"or in a full query, like:
SELECT
":id", -- Socrata column ID
"location",
"projectid",
"project_name", -- Refers to a name generally used to refer to the project. Not all projects have names.
"address", -- Primary street address of project. The street address of a project may change once a land subdivision takes place or an official address is assigned by the City of Cambridge.
"street_number",
"status", -- Refers to the project stage. Options are Permitting, Permit Granted or As of Right, Building Permit Granted, and Complete. See metadata for further details.
"yrcomplete", -- Refers to the year in which a Certificate of Occupancy is granted.
"use_type", -- Projects can include one or more land use types. Projects including multiple land use types will multiple records in this table.
"gfa", -- Total gross floor area (GFA) for the associated use as defined by the zoning ordinance. Other land uses may be included in the project. Other gross floor area may exist on the parcel either in existing or prospective buildings that is not included in the project.
"latitude",
"longitude",
":@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 'location' 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 'location' 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 'location' is located. This enables the creation of region maps (choropleths) in the visualization canvas and data lens.
"street_name",
":@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 'location' 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 'location' is located. This enables the creation of region maps (choropleths) in the visualization canvas and data lens.
FROM
"cambridgema-gov/development-log-historical-projects-use-data-1997-r5mv-isth:latest"."development_log_historical_projects_use_data_1997"
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/development-log-historical-projects-use-data-1997-r5mv-isth 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/development-log-historical-projects-use-data-1997-r5mv-isth: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/development-log-historical-projects-use-data-1997-r5mv-isthCheckout 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/development-log-historical-projects-use-data-1997-r5mv-isth:latestThis will download all the objects for the latest tag of cambridgema-gov/development-log-historical-projects-use-data-1997-r5mv-isth 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/development-log-historical-projects-use-data-1997-r5mv-isth: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/development-log-historical-projects-use-data-1997-r5mv-isth: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/development-log-historical-projects-use-data-1997-r5mv-isth is just another Postgres schema.