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Querying Glean

Glean's query language is called Angle. Read the Angle Guide to learn about how to write Angle queries.

The shell can be used for testing queries and schema changes, and exploring the data.

Query APIs#

There is currently only a Haskell API; APIs in other languages are coming soon.

All client layers are wrappers around the Thrift API.

The results of queries will be returned as instances of the Thrift types in glean/schema/thrift that are generated automatically from the schema.

The client layers provide a few useful things over the raw Thrift API:

  • Connecting to the most recent database for a given repository;
  • Sharding to ensure we connect to a suitable server for that database;
  • In some cases, an API for building queries programmatically.

Thrift#

Glean exposes a Thrift API.

The two methods for querying are

  • userQuery - general queries returning an arbitrary number of results
  • userQueryFacts - fetch the definition of a single fact given its ID

Queries are in Angle syntax, and results are encoded as JSON or Thrift compact which you can encode/decode into the Thrift types.

VS Code syntax highlighter#

A VS Code plugin for Angle syntax highlighting is available in this repository, under glean/vscode/. It can either be built from source and installed, or one can download and install the .vsix file generated by our CI system.

Building from source#

Assuming you have Node JS installed on your system, run the following commands:

cd glean/vscodenpx vsce package

The npx command should produce a glean-x.y.z.vsix file in the glean/vscode/ directory, that you can install in VS Code by following the instructions of the Installing section below.

Downloading from CI#

Simply visit this CI page, click on the latest successful CI run, scroll down to the Artifacts section and click on glean-vsix. This should give you a .zip archive that contains a glean-x.y.z.vsix file that you can install in VS Code by following the instructions in the next section.

Installing#

code --install-extension path/to/glean-x.y.z.vsix

The VS Code documentation describes alternative ways to install an extension from a .vsix file, from within the editor, in case the above command does not work or a more graphical, user-friendly is preferable.