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

时间:2024-09-05 10:32:04

hll_add_agg(hll_hashval, int32 log2m)

描述:把哈希后的数据按照分组放到hll中。并指定参数log2m,取值范围为10~16。

返回值类型:hll

示例:

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 SELECT hll_cardinality(hll_add_agg(hll_hash_text(c), 10)) FROM t_data;
 hll_cardinality  
------------------
 503.932348927339
(1 row)
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