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89 lines
6.7 KiB
Markdown
89 lines
6.7 KiB
Markdown
# system.dictionaries {#system_tables-dictionaries}
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Contains information about [external dictionaries](../../sql-reference/dictionaries/external-dictionaries/external-dicts.md).
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Columns:
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- `database` ([String](../../sql-reference/data-types/string.md)) — Name of the database containing the dictionary created by DDL query. Empty string for other dictionaries.
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- `name` ([String](../../sql-reference/data-types/string.md)) — [Dictionary name](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict.md).
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- `uuid` ([UUID](../../sql-reference/data-types/uuid.md)) — Dictionary UUID.
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- `status` ([Enum8](../../sql-reference/data-types/enum.md)) — Dictionary status. Possible values:
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- `NOT_LOADED` — Dictionary was not loaded because it was not used.
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- `LOADED` — Dictionary loaded successfully.
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- `FAILED` — Unable to load the dictionary as a result of an error.
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- `LOADING` — Dictionary is loading now.
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- `LOADED_AND_RELOADING` — Dictionary is loaded successfully, and is being reloaded right now (frequent reasons: [SYSTEM RELOAD DICTIONARY](../../sql-reference/statements/system.md#query_language-system-reload-dictionary) query, timeout, dictionary config has changed).
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- `FAILED_AND_RELOADING` — Could not load the dictionary as a result of an error and is loading now.
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- `origin` ([String](../../sql-reference/data-types/string.md)) — Path to the configuration file that describes the dictionary.
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- `type` ([String](../../sql-reference/data-types/string.md)) — Type of a dictionary allocation. [Storing Dictionaries in Memory](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-layout.md).
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- `key.names` ([Array](../../sql-reference/data-types/array.md)([String](../../sql-reference/data-types/string.md))) — Array of [key names](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-structure.md#ext_dict_structure-key) provided by the dictionary.
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- `key.types` ([Array](../../sql-reference/data-types/array.md)([String](../../sql-reference/data-types/string.md))) — Corresponding array of [key types](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-structure.md#ext_dict_structure-key) provided by the dictionary.
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- `attribute.names` ([Array](../../sql-reference/data-types/array.md)([String](../../sql-reference/data-types/string.md))) — Array of [attribute names](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-structure.md#ext_dict_structure-attributes) provided by the dictionary.
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- `attribute.types` ([Array](../../sql-reference/data-types/array.md)([String](../../sql-reference/data-types/string.md))) — Corresponding array of [attribute types](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-structure.md#ext_dict_structure-attributes) provided by the dictionary.
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- `bytes_allocated` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Amount of RAM allocated for the dictionary.
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- `query_count` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Number of queries since the dictionary was loaded or since the last successful reboot.
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- `hit_rate` ([Float64](../../sql-reference/data-types/float.md)) — For cache dictionaries, the percentage of uses for which the value was in the cache.
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- `found_rate` ([Float64](../../sql-reference/data-types/float.md)) — The percentage of uses for which the value was found.
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- `element_count` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Number of items stored in the dictionary.
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- `load_factor` ([Float64](../../sql-reference/data-types/float.md)) — Percentage filled in the dictionary (for a hashed dictionary, the percentage filled in the hash table).
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- `source` ([String](../../sql-reference/data-types/string.md)) — Text describing the [data source](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-sources.md) for the dictionary.
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- `lifetime_min` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Minimum [lifetime](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-lifetime.md) of the dictionary in memory, after which ClickHouse tries to reload the dictionary (if `invalidate_query` is set, then only if it has changed). Set in seconds.
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- `lifetime_max` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Maximum [lifetime](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-lifetime.md) of the dictionary in memory, after which ClickHouse tries to reload the dictionary (if `invalidate_query` is set, then only if it has changed). Set in seconds.
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- `loading_start_time` ([DateTime](../../sql-reference/data-types/datetime.md)) — Start time for loading the dictionary.
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- `last_successful_update_time` ([DateTime](../../sql-reference/data-types/datetime.md)) — End time for loading or updating the dictionary. Helps to monitor some troubles with external sources and investigate causes.
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- `loading_duration` ([Float32](../../sql-reference/data-types/float.md)) — Duration of a dictionary loading.
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- `last_exception` ([String](../../sql-reference/data-types/string.md)) — Text of the error that occurs when creating or reloading the dictionary if the dictionary couldn’t be created.
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- `comment` ([String](../../sql-reference/data-types/string.md)) — Text of the comment to dictionary.
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**Example**
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Configure the dictionary:
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``` sql
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CREATE DICTIONARY dictionary_with_comment
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(
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id UInt64,
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value String
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)
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PRIMARY KEY id
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SOURCE(CLICKHOUSE(HOST 'localhost' PORT tcpPort() TABLE 'source_table'))
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LAYOUT(FLAT())
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LIFETIME(MIN 0 MAX 1000)
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COMMENT 'The temporary dictionary';
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```
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Make sure that the dictionary is loaded.
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``` sql
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SELECT * FROM system.dictionaries LIMIT 1 FORMAT Vertical;
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```
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``` text
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Row 1:
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──────
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database: default
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name: dictionary_with_comment
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uuid: 4654d460-0d03-433a-8654-d4600d03d33a
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status: NOT_LOADED
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origin: 4654d460-0d03-433a-8654-d4600d03d33a
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type:
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key.names: ['id']
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key.types: ['UInt64']
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attribute.names: ['value']
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attribute.types: ['String']
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bytes_allocated: 0
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query_count: 0
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hit_rate: 0
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found_rate: 0
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element_count: 0
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load_factor: 0
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source:
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lifetime_min: 0
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lifetime_max: 0
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loading_start_time: 1970-01-01 00:00:00
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last_successful_update_time: 1970-01-01 00:00:00
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loading_duration: 0
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last_exception:
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comment: The temporary dictionary
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```
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