ClickHouse/docs/en/query_language/dicts/external_dicts_dict.md

Configuring an External Dictionary

If dictionary is configured using xml file, than dictionary configuration has the following structure:

<dictionary>
    <name>dict_name</name>

    <structure>
      <!-- Complex key configuration -->
    </structure>

    <source>
      <!-- Source configuration -->
    </source>

    <layout>
      <!-- Memory layout configuration -->
    </layout>

    <lifetime>
      <!-- Lifetime of dictionary in memory -->
    </lifetime>
</dictionary>

Corresponding DDL-query has the following structure:

CREATE DICTIONARY dict_name
(
    ... -- attributes
)
PRIMARY KEY ... -- complex or single key configuration
SOURCE(...) -- Source configuration
LAYOUT(...) -- Memory layout configuration
LIFETIME(...) -- Lifetime of dictionary in memory

• name – The identifier that can be used to access the dictionary. Use the characters [a-zA-Z0-9_\-].
• source — Source of the dictionary.
• layout — Dictionary layout in memory.
• structure — Structure of the dictionary . A key and attributes that can be retrieved by this key.
• lifetime — Frequency of dictionary updates.

Original article