num-datafusion-threads - Amazon Timestream

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num-datafusion-threads

Parameter Details
DefaultSystem logical core count (number of vCPUs)
Allowed ValuesInteger: 1 – 2,048
CategoryQuery Execution

Detailed Explanation:

Sets the number of worker threads that the DataFusion query engine uses for parallel query execution. Each thread can independently process query partitions, enabling parallelism within a single query as well as across multiple concurrent queries.

Impact:

  • Too low: Queries execute serially or with minimal parallelism, leading to high query latency. CPU resources remain underutilized.

  • Too high: Excessive thread contention, context switching overhead, and potential memory pressure.

  • Optimal: Set to the number of available vCPUs. If you are using read-only nodes you can assign more than 1 thread per vCPU, but we recommend extensive testing.

Recommendation: Set to the number of vCPUs on your instance.