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Clickhouse Data Demo
HTTP 200 Row 1: ────── Timestamp: 2025-05-27 14:51:23.678999930 TraceId: 3ea85b7f222073a42cd2d37c1c79ec08 SpanId: 24c7fa0f64ae344a ParentSpanId: TraceState: SpanName: ExecuteRequest SpanKind: Internal Servic...
ClickHouse Schema
otel_traces CREATE TABLE default.otel_traces ( `Timestamp` DateTime64(9) CODEC(Delta(8), ZSTD(1)), `TraceId` String CODEC(ZSTD(1)), `SpanId` String CODEC(ZSTD(1)), `ParentSpanId` String CODEC(ZSTD(1)), `TraceState` String CODEC(ZSTD(1)), ...
Database Metrics Doesn't Exist
Errors Key errors{ "kind": "exporter", "data_type": "logs", "name": "clickhouse", "error": "PrepareContext:code: 81, message: Database metrics doesn't exist", "interval": "14.932404217s" } Source2025-01-08T03:43:01.128Z info internal/retr...
LowCardinality(T)
Description LowCardinality is an optimized column encoding type in ClickHouse, specifically designed to reduce storage space for columns with many duplicate values and accelerate query efficiency. It is particularly suitable for "tags", "status codes", "types...
Data Sharding
数据分片定义 数据分片（Sharding） 是一种将大数据集拆分成多个小数据集并存储在不同服务器上的方法，常用于数据库、分布式存储、对象存储等系统，以提高性能、可扩展性和数据管理效率。 简单来说，分片 = 分而治之，把一大块数据拆成多小块，这样查询、存储和计算都能并行执行，提高效率。 数据分片的常见方式 数据分片一般有 水平分片（Horizontal Sharding） 和 垂直分片（Vertical Sharding） 两种主要方式。 水平分片（Horizontal Sharding） 把同一个表的数据拆分...
Disk Usage SQL
Disk Info SELECT name, path, formatReadableSize(free_space) AS free, formatReadableSize(total_space) AS total FROM system.disks; ┌─name────┬─path─────────────────┬─free───────┬─total──────┐ │ default │ /var/lib/clickhouse/ │ 225.87 GiB │ 491...
Mutations and Processes
Syatem.mutations Get Recently SELECT * FROM system.mutations WHERE is_done = 0 ORDER BY create_time LIMIT 5\G Row 1: ────── database: journal table: otel_logs mutation_id: mutation_6444807.txt command: ...
Shard & Replicas
Table Engine
The MergeTree engine and other engines of the MergeTree family (e.g. ReplacingMergeTree, AggregatingMergeTree ) are the most commonly used and most robust table engines in ClickHouse. Main features of MergeTree family table engines. The primary key does not r...
Table TTL
https://clickhouse.com/docs/sql-reference/functions/date-time-functions Precise TTL TTL is relative to the exact datetime (e.g., 2025-06-05 15:42:30). 1 month - varying daysALTER TABLE journal.otel_logs MODIFY TTL toDateTime(Timestamp) + toIntervalMonth(1); ...
OPTIMIZE Statement
https://clickhouse.com/docs/sql-reference/statements/optimize Introduction Merge Multiple Parts into Fewer or Single Parts Merges multiple data parts (files) into one, reducing fragmentation and improving query performance. Only affects parts within the sam...
Tomato Data Stats
2025-01-22 Table Size┌─database─┬─table───────────────────┬─size───────┬───────rows─┬───bytes_size─┬─latest_modification─┐ │ system │ part_log_0 │ 110.05 GiB │ 1983769703 │ 118170162389 │ 2025-01-22 00:16:21 │ │ journal │ otel_logs ...
Truncate Table
TRUNCATE TABLE default.jaeger_span; It will report error Reason: 1. Size (51.37 GB) is greater than max_[table/partition]_size_to_drop (50.00 GB) 2. File '/bitnami/clickhouse/data/flags/force_drop_table' intended to force DROP doesn't exist How to fix this: 1...