External Dictionaries

    ClickHouse:

    • Fully or partially stores dictionaries in RAM.
    • Periodically updates dictionaries and dynamically loads missing values. In other words, dictionaries can be loaded dynamically.

    The configuration of external dictionaries can be located in one or more xml-files. The path to the configuration is specified in the dictionaries_config parameter.

    The system table contains information about dictionaries configured at server. For each dictionary you can find there:

    • Status of the dictionary.
    • Configuration parameters.
    • Metrics like amount of RAM allocated for the dictionary or a number of queries since the dictionary was successfully loaded.

    The dictionary configuration file has the following format:

    DDL queries for dictionaries doesn’t require any additional records in server configuration. They allow to work with dictionaries as first-class entities, like tables or views.

    Attention