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* Corrected en files * Split system-tables.md into separate files * Fixed links. * Fixed links. * Fixed links. * Fixed links. * Add ref to original article * Fixed links * Add toc_folder_title and translate * Add stack_trace.md, correct toc-title * Fixed links * Hypothesis testing * Hypothesis testing * Update run.sh, thanks @azat Co-authored-by: Anna Devyatova <annadevyatova@yandex-team.ru> Co-authored-by: Sergei Shtykov <bayonet@yandex-team.ru> Co-authored-by: alexey-milovidov <milovidov@yandex-team.ru>
63 lines
7.4 KiB
Markdown
63 lines
7.4 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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- `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` — [Key type](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-structure.md#ext_dict_structure-key): Numeric Key ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) or Сomposite key ([String](../../sql-reference/data-types/string.md)) — form “(type 1, type 2, …, type n)”.
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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) that are 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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- `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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**Example**
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Configure the dictionary.
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``` sql
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CREATE DICTIONARY dictdb.dict
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(
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`key` Int64 DEFAULT -1,
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`value_default` String DEFAULT 'world',
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`value_expression` String DEFAULT 'xxx' EXPRESSION 'toString(127 * 172)'
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)
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PRIMARY KEY key
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SOURCE(CLICKHOUSE(HOST 'localhost' PORT 9000 USER 'default' TABLE 'dicttbl' DB 'dictdb'))
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LIFETIME(MIN 0 MAX 1)
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LAYOUT(FLAT())
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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
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```
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``` text
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┌─database─┬─name─┬─status─┬─origin──────┬─type─┬─key────┬─attribute.names──────────────────────┬─attribute.types─────┬─bytes_allocated─┬─query_count─┬─hit_rate─┬─element_count─┬───────────load_factor─┬─source─────────────────────┬─lifetime_min─┬─lifetime_max─┬──loading_start_time─┌──last_successful_update_time─┬──────loading_duration─┬─last_exception─┐
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│ dictdb │ dict │ LOADED │ dictdb.dict │ Flat │ UInt64 │ ['value_default','value_expression'] │ ['String','String'] │ 74032 │ 0 │ 1 │ 1 │ 0.0004887585532746823 │ ClickHouse: dictdb.dicttbl │ 0 │ 1 │ 2020-03-04 04:17:34 │ 2020-03-04 04:30:34 │ 0.002 │ │
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└──────────┴──────┴────────┴─────────────┴──────┴────────┴──────────────────────────────────────┴─────────────────────┴─────────────────┴─────────────┴──────────┴───────────────┴───────────────────────┴────────────────────────────┴──────────────┴──────────────┴─────────────────────┴──────────────────────────────┘───────────────────────┴────────────────┘
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```
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[Original article](https://clickhouse.tech/docs/en/operations/system_tables/dictionaries) <!--hide--> |