Caching, Throttling, and Update Cost
Summary
Caching reduces repeated computation; throttling limits how often recalculation, publication, or live delivery can occur.
Core Idea
Cache when the same expensive intermediate result is reused. Throttle when a correct result is being produced more frequently than consumers need.
How It Works
U.CACHE stores data under a reusable or read-once key. A numeric block value can throttle supported actions. U.PUB_THROTTLE_MILLIS controls publishing, while U.RTD_THROTTLE_MILLIS controls RTD or Runline subscription update pacing.
Why It Matters
These controls act at different layers. Increasing the wrong throttle can hide updates without reducing the expensive calculation that caused the load.
In Excel (Runline U)
Measure the slow or noisy path first. Apply one control at the narrowest effective point, then verify both calculation cost and acceptable freshness.
Common Patterns
- Cache a large report before several filters and aggregations reuse it.
- Use a read-once cache inside nested U transformations.
- Throttle live dashboards while leaving source calculations responsive.
Misconceptions
- A cache is not automatically refreshed just because its consumers recalculate.
- Publish throttling, HTML throttling, recalculation pacing, and RTD throttling are not equivalent.