uniqCombined 计算不同参数值的近似数量。 语法 uniqCombined(HLL_precision)(x[,...]) 该uniqCombined函数是计算不同值数量的不错选择。 参数 该函数采用可变数量的参数。 参数可以是Tuple,Array,Date,DateTime,String,或数字类型。 HLL_precision是以2为底的单元格数的对数HyperLogLog。可选,您可以将该函数用作...
uniqCombined函数在ClickHouse中的作用 uniqCombined函数是ClickHouse中的一个聚合函数,用于计算一组数据中的唯一值数量。与uniq函数不同的是,uniqCombined采用了更高效的算法来处理大数据集,特别是当数据中存在大量重复值时。它通过合并相同的数据块来减少内存占用,从而提高了性能。 uniqCombined函数的使用场景 uniqCombined函数...
uniqCombined with default values is somewhat more accurate than uniq. uniqCombined is more accurate and takes up less memory and disk space. But usually slower. I (Denis) suggest to try uniqCombined64(15) -- it boosts queries up to 10 times for my distributed queries (1Gbit network). And ...
Describe the unexpected behaviour clickhouse-cloud :) SELECT count(), uniq(*) AS a, uniqCombined(*) AS b FROM planes_mercator \G SELECT count(), uniq(*) AS a, uniqCombined(*) AS b FROM planes_mercator Query id: 5202ef0c-5f71-455c-af0f-95...
更多“ClickHouse中的uniqCombined算子底层采用类似HyperLogLog算法实现,可以实现精准去重。()……”相关的问题 第1题 MRS中的ClickHouse基于ELB(Elastic Load Balance)实现高可用HA部署。() 正确 错误 点击查看答案 第2题 阿里云数据库支持以下哪些数据库引擎()。
44_ClickHouse高级_单表查询优化_使用uniqCombined 1084 播放月光自白书 月光光看书 收藏 下载 分享 手机看 登录后可发评论 评论沙发是我的～选集(93) 自动播放 [1] 01_ClickHouse总体_课... 4052播放 13:18 [2] 02_ClickHouse入门_课... 1449播放 03:24 [3] 02_ClickHouse入门_课... 1342...
uniqCombined Приближённовычисляетколичестворазличныхзначенийаргумента. uniqCombined(HLL_precision)(x[,...]) ФункцияuniqCombined— этохорошийвыбордлявычисленияколичествар...
https://s3.amazonaws.com/clickhouse-test-reports/0/686d6d676ac13a2265538cce17db94f4602c749a/ast_fuzzer__asan_.html SELECT sum(u) FROM ( SELECT intDiv(number, 4096) AS k, uniqCombined(tuple(materialize(toLowCardinality(toNullable(16))) ...
uniqCombined(HLL_precision)(x[,...]) TheuniqCombinedfunction is a good choice for calculating the number of different values. Arguments HLL_precision: The base-2 logarithm of the number of cells inHyperLogLog. Optional, you can use the function asuniqCombined(x[, ...]). The default value ...