数据仓库服务 GaussDB(DWS)-聚合函数:hll_add_agg(hll_hashval, int32 log2m, int32 regwidth)

时间:2025-02-12 15:05:10

hll_add_agg(hll_hashval, int32 log2m, int32 regwidth)

描述:把哈希后的数据按照分组放到hll中。依次指定参数log2m,regwidth。 regwidth取值范围为1~5。

返回值类型:hll

示例:

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SELECT hll_cardinality(hll_add_agg(hll_hash_text(c), NULL, 1)) FROM t_data; hll_cardinality  ------------------ 496.628982624022(1 row)
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