Add a setting scheduler_process_partial that allows partial scheduling of tasks in the background threads#16973
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Mytherin merged 6 commits intoduckdb:mainfrom Apr 4, 2025
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… PROCESS_ALL we use PROCESS_PARTIAL to partially process tasks and then reschedule for more fairness between queries
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Add a setting `scheduler_process_partial` that allows partial scheduling of tasks in the background threads (duckdb/duckdb#16973)
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Add a setting `scheduler_process_partial` that allows partial scheduling of tasks in the background threads (duckdb/duckdb#16973)
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Add a setting `scheduler_process_partial` that allows partial scheduling of tasks in the background threads (duckdb/duckdb#16973)
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Add a setting `scheduler_process_partial` that allows partial scheduling of tasks in the background threads (duckdb/duckdb#16973)
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Add a setting `scheduler_process_partial` that allows partial scheduling of tasks in the background threads (duckdb/duckdb#16973)
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This PR adds a new setting -
scheduler_process_partial- that allows partial scheduling of tasks in the background threads. Normally, the background tasks passTaskExecutionMode::PROCESS_ALLto the tasks they execute - leading to them being stuck on processing the task fully until it is completed. As a result, long-running queries can block short-running queries.In regular DuckDB operation - that is not a big problem, because every connection has its own "processing thread" that works only on the queries it issues - and hence short-running queries still make some progress. That is not always the case - however. When using certain APIs (e.g. the pending query API) the foreground thread might not participate in the query processing, leaving everything to the background tasks. As a result, short-running queries can become starved.
Enabling this setting improves fairness by only working on tasks partially before rescheduling. As a result, bigger tasks will need more "rounds" and short-running queries will complete without stalling. The setting is disabled by default for now as in most instances this will not be required - but is enabled in CI with the alternative verification setting.