Clickhouse自帶系統庫system，啓動時創建系統表，無數據文件，主要用於記錄系統信息，我們可以同過系統表來查看clickhouse運行狀態。
processes：當前連接進程信息
>select query_id,initial_user,initial_address,elapsed,query from system.processes;
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is_initial_query: |
1 |
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user: |
default |
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query_id: |
b589a0a1-440a-4cd7-a03e-e6da0ddc427b |
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address: |
127.0.0.1 |
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port: |
39714 |
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initial_user: |
default |
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initial_query_id: |
b589a0a1-440a-4cd7-a03e-e6da0ddc427b |
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initial_address: |
127.0.0.1 |
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initial_port: |
39714 |
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interface: |
1 |
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os_user: |
root |
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client_hostname: |
A01-R21-I55-99-9001887.LOCAL |
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client_name: |
ClickHouse |
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client_version_major: |
18 |
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client_version_minor: |
14 |
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client_version_patch: |
19 |
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client_revision: |
54409 |
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http_method: |
0 |
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http_user_agent: |
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quota_key: |
|
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elapsed: |
0.001502786 |
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is_cancelled: |
0 |
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read_rows: |
0 |
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read_bytes: |
0 |
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total_rows_approx: |
0 |
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written_rows: |
0 |
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written_bytes: |
0 |
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memory_usage: |
0 |
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peak_memory_usage: |
121 |
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query: |
Select * from … |
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thread_numbers: |
[74] |
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ProfileEvents.Names: |
['Query','SelectQuery','ReadCompressedBytes','CompressedReadBufferBlocks','CompressedReadBufferBytes','IOBufferAllocs','IOBufferAllocBytes','ContextLock','RWLockAcquiredReadLocks'] |
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ProfileEvents.Values: |
[1,1,36,1,10,1,57,4,1] |
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Settings.Names: |
['max_threads','max_query_size','queue_max_wait_ms','use_uncompressed_cache','background_pool_size','load_balancing','max_memory_usage'] |
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Settings.Values: |
['48','262144000','5000000','0','64','random','50000000000'] |
replicas：查看當前複製信息
>select database,table,is_leader,is_readonly,is_session_expired,future_parts,parts_to_check,columns_version,queue_size,inserts_in_queue,merges_in_queue,log_max_index,log_pointer,total_replicas,active_replicasFROM system.replicas WHERE is_readonly OR is_session_expired OR future_parts > 20 OR parts_to_check > 10 OR queue_size > 20 OR inserts_in_queue > 10 OR log_max_index - log_pointer > 10 OR total_replicas < 2 OR active_replicas < total_replicas;
如果結果返回有值，則有延遲，需要排查。
asynchronous_metrics：系統性能表，非實時
與metrics計算方式不同，jemalloc是內存分配算法:
metrics：系統信息指標，實時
|
Query |
當前連接數量 |
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Merge |
當前後臺合併數量 |
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PartMutation |
當前更改的數量delete\update |
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ReplicatedFetch |
從副本獲取的數據 |
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ReplicatedSend |
發送到副本的數據 |
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ReplicatedChecks |
一致性校驗的數量 |
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BackgroundPoolTask |
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BackgroundSchedulePoolTask |
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DiskSpaceReservedForMerge |
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DistributedSend |
分佈式表發送遠程的連接數 |
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QueryPreempted |
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TCPConnection |
TCP連接數量 |
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HTTPConnection |
HTTP連接數量 |
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InterserverConnection |
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OpenFileForRead |
打開讀文件數 |
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OpenFileForWrite |
打開寫文件數 |
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Read |
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Write |
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SendExternalTables |
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QueryThread |
查詢處理線程數 |
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ReadonlyReplica |
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LeaderReplica |
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MemoryTracking |
當前查詢內存分配的數量 |
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MemoryTrackingInBackgroundProcessingPool |
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MemoryTrackingInBackgroundSchedulePool |
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MemoryTrackingForMerges |
合併分配的內存數量 |
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LeaderElection |
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EphemeralNode |
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ZooKeeperSession |
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ZooKeeperWatch |
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ZooKeeperRequest |
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DelayedInserts |
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ContextLockWait |
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StorageBufferRows |
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StorageBufferBytes |
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DictCacheRequests |
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Revision |
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RWLockWaitingReaders |
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RWLockWaitingWriters |
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RWLockActiveReaders |
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RWLockActiveWriters |
build_options：軟件信息
|
name |
value |
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VERSION_FULL |
ClickHouse 18.14.19 |
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VERSION_DESCRIBE |
v18.14.19-testing |
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VERSION_GITHASH |
8883b8888de0a4b9b8a1687b450c4dd99a97f066 |
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VERSION_REVISION |
54409 |
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BUILD_DATE |
2018-12-20 |
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BUILD_TYPE |
Release |
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SYSTEM |
Linux-3.10.0-957.1.3.el7.x86_64 |
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SYSTEM_PROCESSOR |
x86_64 |
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LIBRARY_ARCHITECTURE |
|
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CMAKE_VERSION |
3.12.2 |
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C_COMPILER |
/opt/rh/devtoolset-7/root/usr/bin/gcc |
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C_COMPILER_VERSION |
7.3.1 |
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CXX_COMPILER |
/opt/rh/devtoolset-7/root/usr/bin/g++ |
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CXX_COMPILER_VERSION |
7.3.1 |
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C_FLAGS |
-pipe -msse4.1 -msse4.2 -mpopcnt -fno-omit-frame-pointer -Wall -no-pie -O2 -DNDEBUG |
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CXX_FLAGS |
-pipe -msse4.1 -msse4.2 -mpopcnt -fno-omit-frame-pointer -Wall -Wnon-virtual-dtor -no-pie -O2 -DNDEBUG |
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LINK_FLAGS |
-static-libgcc -static-libstdc++ |
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BUILD_COMPILE_DEFINITIONS |
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BUILD_INCLUDE_DIRECTORIES |
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STATIC |
ON |
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USE_EMBEDDED_COMPILER |
0 |
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USE_INTERNAL_MEMCPY |
ON |
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USE_GLIBC_COMPATIBILITY |
ON |
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USE_JEMALLOC |
1 |
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USE_TCMALLOC |
|
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USE_UNWIND |
1 |
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USE_ICU |
1 |
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USE_MYSQL |
1 |
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USE_RE2_ST |
1 |
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USE_VECTORCLASS |
|
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USE_RDKAFKA |
1 |
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USE_CAPNP |
1 |
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USE_POCO_SQLODBC |
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USE_POCO_DATAODBC |
1 |
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USE_POCO_MONGODB |
1 |
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USE_POCO_NETSSL |
1 |
Clusters：集羣信息
>select c.shard_num,c.host_name as master_host,d.host_name as rep_host from (select shard_num,host_name from system.clusters where replica_num=1) as c left join (select shard_num,host_name from system.clusters where replica_num=2) as d on c.shard_num=d.shard_num
cluster：羣集名稱
shard_num：集羣中的分片編號，從1開始
shard_weight：寫入數據時分片的相對權重，1
replica_num：分片中的副本號，從1開始
host_name：主機名，在config中指定
host_address：從DNS獲取的主機IP地址
port：用於連接服務器的端口，9000
is_local： 是不是當前所在機器，1
user：用於連接服務器的用戶的名稱，默認default
data_type_families：數據類型
ClickHouse release 18.16.1版本新加的系統表
name：數據類型名稱
case_insensitive：是否區分大小寫，0不區分，1區分
alias_to：別名，BIGINT=Int64，TEXT=String
collations：字符集排序規則
databases、tables、columns
庫、表、列信息
functions：函數信息
formats：輸出格式
XML、JSON、Vertical、CSV等等
SELECT * FROM system.formats FORMAT JSON；
events：已處理的系統事件監控
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Query |
總查詢數 |
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SelectQuery |
僅select數量 |
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InsertQuery |
僅insert數量 |
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FileOpen |
打開文件數量 |
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ReadBufferFromFileDescriptorRead |
文件描述符的讀取次數 |
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ReadBufferFromFileDescriptorReadBytes |
從文件描述符讀取的字節數 |
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WriteBufferFromFileDescriptorWrite |
文件描述符的寫入次數 |
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WriteBufferFromFileDescriptorWriteBytes |
寫入文件描述符的字節數 |
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InsertedRows |
插入到所有表的行數 |
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MergedRows |
合併前的行數 |
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MergesTimeMilliseconds |
後臺合併花費總時間 |
merges：正在進行合併的信息
|
database: |
db |
|
table: |
table |
|
elapsed: |
0.038135789 |
|
progress: |
0.294799805 |
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num_parts: |
5 |
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source_part_names: |
['20181231_12026210_12026567_44','20181231_12026568_12026568_0','20181231_12026570_12026570_0','20181231_12026572_12026572_0','20181231_12026574_12026574_0'] |
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result_part_name: |
20181231_12026210_12026574_45 |
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partition_id: |
20181231 |
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total_size_bytes_compressed: |
560012 |
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total_size_marks: |
7 |
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bytes_read_uncompressed: |
3824250 |
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rows_read: |
16905 |
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bytes_written_uncompressed: |
1852376 |
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rows_written: |
8192 |
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columns_written: |
0 |
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memory_usage: |
152843009 |
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thread_number: |
62 |
numbers 、numbers_mt：測試使用，從零開始的所有自然數
one：測試使用，類似於其他DBMS中的DUAL表
settings：查看當前設置信息
|
max_threads |
最大線程 |
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max_block_size |
讀取最大塊大小 |
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load_balancing |
random分佈式隨機選取副本 |
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force_primary_key |
強制使用主鍵，無主鍵報錯 |
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force_index_by_date |
強制使用時間，無時間報錯 |
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log_query_settings |
將日誌寫入系統表query_log |
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log_queries |
是否打開全日誌 |
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max_memory_usage |
單個查詢最大使用內存，0爲無限制 |
parts、parts_columns：查看分區表信息
>select database,table,partition_id,partition,name,active,rows,path,modification_time from system.parts where table='';
zookeeper ：未配置ZooKeeper，則表不存在
>select * from system.zookeeper WHERE path = '/clickhouse/tables/02-02/cluster/' and name='metadata' FORMAT Vertical