hll_union_agg

hll_union_agg

hll_union_agg介绍

hll_union_agg(expr, allowDifferentLgConfigK) - 返回估计的独特值数量。allowDifferentLgConfigK（可选）允许具有不同 lgConfigK 值的草图进行合并（默认为 false）。

Examples:

> SELECT hll_sketch_estimate(hll_union_agg(sketch, true)) FROM (SELECT hll_sketch_agg(col) as sketch FROM VALUES (1) tab(col) UNION ALL SELECT hll_sketch_agg(col, 20) as sketch FROM VALUES (1) tab(col));
 1

Since: 3.5.0

hll_unionhour