clickhouse create table 异常：在查询中发现聚合函数 minState(origin_user) 位置错误

Posted 2023-03-25

【中文标题】clickhouse create table 异常：在查询中发现聚合函数 minState(origin_user) 位置错误

【英文标题】：clickhouse create table Exception: Aggregate function minState(origin_user) is found in wrong place in query

【发布时间】：2021-10-17 09:25:20

【问题描述】：

CREATE TABLE user_dwd.user_tag_bitmap_local 
(
    `tag` String,
    `tag_item` String,
    `p_day` Date,
    `origin_user` UInt64,
    `users` AggregateFunction(min, UInt64) MATERIALIZED minState(origin_user)
)
ENGINE = AggregatingMergeTree()
PARTITION BY toYYYYMMDD(p_day)
ORDER BY (tag, tag_item)
SETTINGS index_granularity = 8192;

运行sql建表时，报错：

[2021-10-17 12:05:28] 代码：184，e.displayText() = DB::Exception：在查询中发现聚合函数 minState(origin_user) 位置错误：处理 minState 时(origin_user) AS users_tmp_alter9508717652815860223：默认表达式和列类型不兼容。 （版本 21.8.4.51（正式版））

如何解决错误？

【参考方案1】：

minState 是一个聚合函数，你不能这样使用它（它用于带有 groupby 部分的查询）。 要解决它，您可以使用MATERIALIZED initializeAggregation... 或MATERIALIZED arrayReduce(minState...

但实际上您不需要第二列。 您正在寻找 SimpleAggregateFunction：

https://clickhouse.com/docs/en/sql-reference/data-types/simpleaggregatefunction/

CREATE TABLE user_dwd.user_tag_bitmap_local 
(
    `tag` String,
    `tag_item` String,
    `p_day` Date,
    `origin_user` SimpleAggregateFunction(min, UInt64) ---<<<-----
)
ENGINE = AggregatingMergeTree()
PARTITION BY toYYYYMMDD(p_day)
ORDER BY (tag, tag_item)
SETTINGS index_granularity = 8192;

---

https://clickhouse.com/docs/en/sql-reference/functions/other-functions/#initializeaggregation

CREATE TABLE user_tag_bitmap_local
(
    `tag` String,
    `tag_item` String,
    `p_day` Date,
    `origin_user` UInt64,
    `users` AggregateFunction(min, UInt64) MATERIALIZED initializeAggregation('minState', origin_user)
)
ENGINE = AggregatingMergeTree
PARTITION BY toYYYYMMDD(p_day)
ORDER BY (tag, tag_item)
SETTINGS index_granularity = 8192

https://clickhouse.com/docs/en/sql-reference/functions/array-functions/#arrayreduce

CREATE TABLE user_tag_bitmap_local
(
    `tag` String,
    `tag_item` String,
    `p_day` Date,
    `origin_user` UInt64,
    `users` AggregateFunction(min, UInt64) MATERIALIZED arrayReduce('minState', [origin_user])
)
ENGINE = AggregatingMergeTree
PARTITION BY toYYYYMMDD(p_day)
ORDER BY (tag, tag_item)
SETTINGS index_granularity = 8192