ServiceX

Overview

Provide concise, correct func_adl query patterns for ServiceX on ATLAS xAOD, with best practices for selections, outputs, and deliver usage.

Workflow

1. Identify the dataset type and base query.
   • Use FuncADLQueryPHYSLITE for PHYSLITE or OpenData.
   • Use FuncADLQueryPHYS for PHYS or other derivations.
2. Build a top-level Select that gathers all required collections and singletons.
   • Apply object-level filters with nested .Where inside this Select.
   • Do not pick columns yet.
3. Apply event-level filtering with a top-level .Where after the collections Select.
4. Create a final top-level Select that returns a single dictionary of output columns.
   • Convert units to standard LHC units (GeV, meters, etc.).
   • Never return a nested dictionary.
5. Use deliver once with NFiles=1 by default and appropriate dataset source(s).
6. Make sure that the layout of the data that will be returned is remembered - downstream tasks that want to work with the data will need to understand it.

Core Rules

• Prefer two top-level Select calls: collections first, output columns second.
• Filter objects with nested .Where; filter events with a top-level .Where.
• Use a single final Select that returns a dictionary of outputs.
• Do not use awkward functions inside ServiceX queries.
• Use dataset.Rucio for rucio DIDs and dataset.FileList for URL lists.
• Always set NFiles=1 in deliver by default.
• If a transform fails and logs are required, respond with HELP USER.
• Ensure func_adl_servicex_xaodr25 is listed as a dependency in the active project and installed in the current virtual environment before running or generating code that uses it.

References

• Load references/servicex-hints.md for overall ServiceX query patterns, best practices, and error handling, and template code.
• Load only the relevant xAOD data model topic file(s) to keep context small. Naming convention: references/datamodel-xaod-*.md.
• xAOD topics:
  • references/datamodel-xaod-units.md (standard ATLAS units (energy, etc))
  • references/datamodel-xaod-objects.md (jets, electrons, muons)
  • references/datamodel-xaod-tau.md
  • references/datamodel-xaod-missing-et.md
  • references/datamodel-xaod-tools-btagging.md
  • references/datamodel-xaod-event-weights.md
  • references/datamodel-xaod-tlorentzvector.md