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name: backends description: "Select, register, and troubleshoot Fugue execution backends and plugin packages." metadata: disco-role: operating disable-model-invocation: true license: Apache 2.0

backends

Use this sub-skill for execution-engine and backend-package questions.

Covers

• make_execution_engine(...), engine_context(...), and engine resolution rules
• register_execution_engine(...), register_sql_engine(...), and the default-engine registration helpers
• backend plugin packages and aliases for Native, DuckDB, Dask, Spark, Ray, Ibis, and Polars
• backend import side effects, object inference, and config-specific runtime failures

Excludes

• Workflow DAG mechanics and dataframe transformations, which belong in ../workflow/
• FugueSQL syntax, YIELD, and PRINT, which belong in ../sql/
• Notebook extension setup and %%fsql, which belong in ../notebook/

Read these files

• references/backend-reference.md for the backend matrix, alias map, and resolution order
• references/troubleshooting.md for optional backend failures and service-specific issues
• scripts/smoke_backends.py for a safe import-and-registration smoke check

Typical user prompts

• "Why does Fugue not recognize my Spark/Dask/Ray object?"
• "How do I select a DuckDB or Spark execution engine?"
• "How do I register a custom execution engine with Fugue?"
• "Which Fugue extra do I need for notebook, DuckDB, or Polars support?"

If the task is mainly about writing the dataframe workflow or FugueSQL text that happens to run on a backend, open the workflow or SQL sub-skill first and only come here for engine selection details.