estdc() returns the estimated count of the distinct values in the table column.

index=f17 | chart estdc(_time) by host

estdc() receives parameter changes with following conditions: columns you want distinct count values and the maximum relative standard deviation (rsd) allowed. In DPL, the default rsd is 0.05 and is not changeable for estdc(). For lower than 0.01 rsd it is more efficient to use distinct_count() function.