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 tests_for_antibodies_to_trachoma_pgp3_antigen
table in this repository, by referencing it like:
"cdc-gov/tests-for-antibodies-to-trachoma-pgp3-antigen-pwgb-7r9t:latest"."tests_for_antibodies_to_trachoma_pgp3_antigen"
or in a full query, like:
SELECT
":id", -- Socrata column ID
"lfa_2", -- Combined LFA test result using 2 categories from blood and serum -.-, Serum negative, blood negative; +.- Serum positive, blood negative; -.+ Serum negative, blood positive; +.+ Serum positive, blood positive
"lfa_3", -- Combined LFA test result using 3 categories from blood and serum -.- Serum negative, blood negative; ?.- Serum indeterminate, blood negative; +.- Serum positive, blood negative; ?.? Serum indeterminate, blood indeterminate; +.? Serum positive, blood indeterminate; -.+ Serum negative, blood positive; ?.+ Serum indeterminate, blood positive; +.+ Serum positive, blood positive
"elisa_pre_dx_mt", -- ELISA pre-coated sample qualitative value (mixture model cutoff) - Negative, + Positive
"elisa_pre_od", -- ELISA OD value, pre-coated sample
"elisa_od", -- ELISA OD value, freshly-coated sample
"luminex_dx", -- Luminex qualitative value (2 categories) - Negative, + Positive
"luminex_mfi", -- Luminex MFI value
"sampleid", -- Unique identification number
"elisa_pre", -- ELISA pre-coated sample qualitative value (3 categories) - Negative, ? Indeterminate, + Positive
"elisa_dx", -- ELISA freshly-coated sample qualitative value (2 categories) - Negative, + Positive
"elisa_dx_mt", -- ELISA freshly-coated sample qualitative value (mixture model cutoff) - Negative, + Positive
"sex", -- Sex 1=male, 2=female
"lfa_serum", -- LFA test result, serum sample, with indeterminate results - Negative, ? Indeterminate, + Positive
"lfa_blood", -- LFA test result, blood sample, with indeterminate results - Negative, ? Indeterminate, + Positive
"elisa", -- ELISA freshly-coated sample qualitative value (3 categories) - Negative, ? Indeterminate, + Positive
"lfa_blood_2", -- LFA test result, serum sample, with indeterminate results treated as missing - Negative, + Positive
"lfa_serum_2", -- LFA test result, serum sample, with indeterminate results treated as missing - Negative, + Positive
"elisa_pre_dx", -- ELISA pre-coated sample qualitative value (2 categories) - Negative, + Positive
"luminex", -- Luminex qualitative value (3 categories) - Negative, ? Indeterminate, + Positive
"age_f", -- age category (0,10] = 0-10 years old, (10,20] = 11-20 years old,
"age" -- data not included
FROM
"cdc-gov/tests-for-antibodies-to-trachoma-pgp3-antigen-pwgb-7r9t:latest"."tests_for_antibodies_to_trachoma_pgp3_antigen"
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 cdc-gov/tests-for-antibodies-to-trachoma-pgp3-antigen-pwgb-7r9t
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; sgr
can 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 clone
and sgr checkout
.
Cloning Data
Because cdc-gov/tests-for-antibodies-to-trachoma-pgp3-antigen-pwgb-7r9t: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 cdc-gov/tests-for-antibodies-to-trachoma-pgp3-antigen-pwgb-7r9t
Checkout 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 cdc-gov/tests-for-antibodies-to-trachoma-pgp3-antigen-pwgb-7r9t:latest
This will download all the objects for the latest
tag of cdc-gov/tests-for-antibodies-to-trachoma-pgp3-antigen-pwgb-7r9t
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 cdc-gov/tests-for-antibodies-to-trachoma-pgp3-antigen-pwgb-7r9t: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 cdc-gov/tests-for-antibodies-to-trachoma-pgp3-antigen-pwgb-7r9t:latest
This 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, cdc-gov/tests-for-antibodies-to-trachoma-pgp3-antigen-pwgb-7r9t
is just another Postgres schema.