检查是否使用 clickhouse-client 应用了设置答案

【问题标题】：Check if a setting was applied with clickhouse-client检查是否使用 clickhouse-client 应用了设置
【发布时间】：2021-09-24 18:58:46
【问题描述】：

如何检查服务器上是否应用了集群设置？

例如，我在集群上运行--query "SET allow_experimental_live_view = 1"。我应该使用哪个查询来检查此设置是否已更改？是否可以使用 clickhouse-client 命令？

这个问题很相似，但没有回答我的How to check whether Clickhouse server-settings is really applied?

【问题讨论】：

标签： clickhouse clickhouse-client

【解决方案1】：

clickhouse-client 有很多选项。让我们检查一下：

clickhouse-client --help

...
  --allow_experimental_live_view arg                               Enable LIVE VIEW. Not mature enough.
  --live_view_heartbeat_interval arg                               The heartbeat interval in seconds to indicate live query is alive.
  --max_live_view_insert_blocks_before_refresh arg                 Limit maximum number of inserted blocks after which mergeable blocks are dropped and query is re-executed.
...

需要这样传递：

clickhouse-client --allow_experimental_live_view 1

要检查当前设置，请使用：

SELECT *
FROM system.settings
WHERE name LIKE '%_live_%'

┌─name───────────────────────────────────────┬─value─┬─changed─┬─description────────────────────────────────────────────────────────────────────────────────────────────────┬─min──┬─max──┬─readonly─┬─type────┐
│ tcp_keep_alive_timeout                     │ 0     │       0 │ The time in seconds the connection needs to remain idle before TCP starts sending keepalive probes         │ ᴺᵁᴸᴸ │ ᴺᵁᴸᴸ │        0 │ Seconds │
│ allow_experimental_live_view               │ 1     │       1 │ Enable LIVE VIEW. Not mature enough.                                                                       │ ᴺᵁᴸᴸ │ ᴺᵁᴸᴸ │        0 │ Bool    │
│ max_live_view_insert_blocks_before_refresh │ 64    │       0 │ Limit maximum number of inserted blocks after which mergeable blocks are dropped and query is re-executed. │ ᴺᵁᴸᴸ │ ᴺᵁᴸᴸ │        0 │ UInt64  │
│ temporary_live_view_timeout                │ 5     │       0 │ Timeout after which temporary live view is deleted.                                                        │ ᴺᵁᴸᴸ │ ᴺᵁᴸᴸ │        0 │ Seconds │
│ periodic_live_view_refresh                 │ 60    │       0 │ Interval after which periodically refreshed live view is forced to refresh.                                │ ᴺᵁᴸᴸ │ ᴺᵁᴸᴸ │        0 │ Seconds │
└────────────────────────────────────────────┴───────┴─────────┴────────────────────────────────────────────────────────────────────────────────────────────────────────────┴──────┴──────┴──────────┴─────────┘

要围绕所有集群节点运行此查询，请参阅is there a better way to query system tables across a clickhouse cluster?。

【讨论】：