Basic Concepts
Concepts
- cluster
Cluster: Cluster is a logical concept in ClickHouse. It can be defined by users as required, which is different from the general understanding of cluster. Multiple ClickHouse nodes are loosely coupled and exist independently.
- shards
Shard: A shard is a horizontal division of a cluster. A cluster can consist of multiple shards.
- replicas
Replica: One shard can contain multiple replicas.
- partition
Partition: A partition is used for local replicas and can be considered as a vertical division.
- MergeTree
ClickHouse has a huge table engine system. As the basic table engine of the family system, MergeTree provides functions such as data partitioning, primary indexes, and secondary indexes. When creating a table, you need to specify the table engine. Different table engines determine the final character of a data table, for example, the features of a data table, the form how data is stored, and how data is loaded.
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