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distinctcounthll-1.md

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description
This section contains reference documentation for the DISTINCTCOUNTHLL function.

DISTINCTCOUNTHLLPLUS

Signature

DISTINCTCOUNTHLLPLUS(colName, log2m)

Usage Examples

DISTINCTCOUNTHLLPLUS considerations

  • DISTINCTCOUNTHLL()is faster than DISTINCTCOUNT()if data is pre-aggregated at ingestion or aggregated at a server with enough records. This performance improvement increases when comparing large datasets.
  • If very few records are pre-aggregated, DISTINCTCOUNTHLL()will not be as fast as DISTINCTCOUNT()because the serialized HLL size is larger than sending individual values.
  • DISTINCTCOUNTHLLPLUS()provides more precise results than DISTINCTCOUNTHLL()with the same performance.
  • DISTINCTCOUNTSMARTHLL()automatically shifts to HLL when reaching a threshold, and comes with some overhead.