mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-16 20:53:27 +00:00
444 lines
15 KiB
Markdown
444 lines
15 KiB
Markdown
---
|
||
toc_priority: 58
|
||
toc_title: External Dictionaries
|
||
---
|
||
|
||
!!! attention "Attention"
|
||
For dictionaries, created with [DDL queries](../../sql-reference/statements/create/dictionary.md), the `dict_name` parameter must be fully specified, like `<database>.<dict_name>`. Otherwise, the current database is used.
|
||
|
||
# Functions for Working with External Dictionaries {#ext_dict_functions}
|
||
|
||
For information on connecting and configuring external dictionaries, see [External dictionaries](../../sql-reference/dictionaries/external-dictionaries/external-dicts.md).
|
||
|
||
## dictGet, dictGetOrDefault, dictGetOrNull {#dictget}
|
||
|
||
Retrieves values from an external dictionary.
|
||
|
||
``` sql
|
||
dictGet('dict_name', attr_names, id_expr)
|
||
dictGetOrDefault('dict_name', attr_names, id_expr, default_value_expr)
|
||
dictGetOrNull('dict_name', attr_name, id_expr)
|
||
```
|
||
|
||
**Arguments**
|
||
|
||
- `dict_name` — Name of the dictionary. [String literal](../../sql-reference/syntax.md#syntax-string-literal).
|
||
- `attr_names` — Name of the column of the dictionary, [String literal](../../sql-reference/syntax.md#syntax-string-literal), or tuple of column names, [Tuple](../../sql-reference/data-types/tuple.md)([String literal](../../sql-reference/syntax.md#syntax-string-literal)).
|
||
- `id_expr` — Key value. [Expression](../../sql-reference/syntax.md#syntax-expressions) returning dictionary key-type value or [Tuple](../../sql-reference/data-types/tuple.md)-type value depending on the dictionary configuration.
|
||
- `default_value_expr` — Values returned if the dictionary does not contain a row with the `id_expr` key. [Expression](../../sql-reference/syntax.md#syntax-expressions) or [Tuple](../../sql-reference/data-types/tuple.md)([Expression](../../sql-reference/syntax.md#syntax-expressions)), returning the value (or values) in the data types configured for the `attr_names` attribute.
|
||
|
||
**Returned value**
|
||
|
||
- If ClickHouse parses the attribute successfully in the [attribute’s data type](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-structure.md#ext_dict_structure-attributes), functions return the value of the dictionary attribute that corresponds to `id_expr`.
|
||
|
||
- If there is no the key, corresponding to `id_expr`, in the dictionary, then:
|
||
|
||
- `dictGet` returns the content of the `<null_value>` element specified for the attribute in the dictionary configuration.
|
||
- `dictGetOrDefault` returns the value passed as the `default_value_expr` parameter.
|
||
- `dictGetOrNull` returns `NULL` in case key was not found in dictionary.
|
||
|
||
ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.
|
||
|
||
**Example for simple key dictionary**
|
||
|
||
Create a text file `ext-dict-test.csv` containing the following:
|
||
|
||
``` text
|
||
1,1
|
||
2,2
|
||
```
|
||
|
||
The first column is `id`, the second column is `c1`.
|
||
|
||
Configure the external dictionary:
|
||
|
||
``` xml
|
||
<clickhouse>
|
||
<dictionary>
|
||
<name>ext-dict-test</name>
|
||
<source>
|
||
<file>
|
||
<path>/path-to/ext-dict-test.csv</path>
|
||
<format>CSV</format>
|
||
</file>
|
||
</source>
|
||
<layout>
|
||
<flat />
|
||
</layout>
|
||
<structure>
|
||
<id>
|
||
<name>id</name>
|
||
</id>
|
||
<attribute>
|
||
<name>c1</name>
|
||
<type>UInt32</type>
|
||
<null_value></null_value>
|
||
</attribute>
|
||
</structure>
|
||
<lifetime>0</lifetime>
|
||
</dictionary>
|
||
</clickhouse>
|
||
```
|
||
|
||
Perform the query:
|
||
|
||
``` sql
|
||
SELECT
|
||
dictGetOrDefault('ext-dict-test', 'c1', number + 1, toUInt32(number * 10)) AS val,
|
||
toTypeName(val) AS type
|
||
FROM system.numbers
|
||
LIMIT 3;
|
||
```
|
||
|
||
``` text
|
||
┌─val─┬─type───┐
|
||
│ 1 │ UInt32 │
|
||
│ 2 │ UInt32 │
|
||
│ 20 │ UInt32 │
|
||
└─────┴────────┘
|
||
```
|
||
|
||
**Example for complex key dictionary**
|
||
|
||
Create a text file `ext-dict-mult.csv` containing the following:
|
||
|
||
``` text
|
||
1,1,'1'
|
||
2,2,'2'
|
||
3,3,'3'
|
||
```
|
||
|
||
The first column is `id`, the second is `c1`, the third is `c2`.
|
||
|
||
Configure the external dictionary:
|
||
|
||
``` xml
|
||
<clickhouse>
|
||
<dictionary>
|
||
<name>ext-dict-mult</name>
|
||
<source>
|
||
<file>
|
||
<path>/path-to/ext-dict-mult.csv</path>
|
||
<format>CSV</format>
|
||
</file>
|
||
</source>
|
||
<layout>
|
||
<flat />
|
||
</layout>
|
||
<structure>
|
||
<id>
|
||
<name>id</name>
|
||
</id>
|
||
<attribute>
|
||
<name>c1</name>
|
||
<type>UInt32</type>
|
||
<null_value></null_value>
|
||
</attribute>
|
||
<attribute>
|
||
<name>c2</name>
|
||
<type>String</type>
|
||
<null_value></null_value>
|
||
</attribute>
|
||
</structure>
|
||
<lifetime>0</lifetime>
|
||
</dictionary>
|
||
</clickhouse>
|
||
```
|
||
|
||
Perform the query:
|
||
|
||
``` sql
|
||
SELECT
|
||
dictGet('ext-dict-mult', ('c1','c2'), number) AS val,
|
||
toTypeName(val) AS type
|
||
FROM system.numbers
|
||
LIMIT 3;
|
||
```
|
||
|
||
``` text
|
||
┌─val─────┬─type──────────────────┐
|
||
│ (1,'1') │ Tuple(UInt8, String) │
|
||
│ (2,'2') │ Tuple(UInt8, String) │
|
||
│ (3,'3') │ Tuple(UInt8, String) │
|
||
└─────────┴───────────────────────┘
|
||
```
|
||
|
||
**Example for range key dictionary**
|
||
|
||
Input table:
|
||
|
||
```sql
|
||
CREATE TABLE range_key_dictionary_source_table
|
||
(
|
||
key UInt64,
|
||
start_date Date,
|
||
end_date Date,
|
||
value String,
|
||
value_nullable Nullable(String)
|
||
)
|
||
ENGINE = TinyLog();
|
||
|
||
INSERT INTO range_key_dictionary_source_table VALUES(1, toDate('2019-05-20'), toDate('2019-05-20'), 'First', 'First');
|
||
INSERT INTO range_key_dictionary_source_table VALUES(2, toDate('2019-05-20'), toDate('2019-05-20'), 'Second', NULL);
|
||
INSERT INTO range_key_dictionary_source_table VALUES(3, toDate('2019-05-20'), toDate('2019-05-20'), 'Third', 'Third');
|
||
```
|
||
|
||
Create the external dictionary:
|
||
|
||
```sql
|
||
CREATE DICTIONARY range_key_dictionary
|
||
(
|
||
key UInt64,
|
||
start_date Date,
|
||
end_date Date,
|
||
value String,
|
||
value_nullable Nullable(String)
|
||
)
|
||
PRIMARY KEY key
|
||
SOURCE(CLICKHOUSE(HOST 'localhost' PORT tcpPort() TABLE 'range_key_dictionary_source_table'))
|
||
LIFETIME(MIN 1 MAX 1000)
|
||
LAYOUT(RANGE_HASHED())
|
||
RANGE(MIN start_date MAX end_date);
|
||
```
|
||
|
||
Perform the query:
|
||
|
||
``` sql
|
||
SELECT
|
||
(number, toDate('2019-05-20')),
|
||
dictHas('range_key_dictionary', number, toDate('2019-05-20')),
|
||
dictGetOrNull('range_key_dictionary', 'value', number, toDate('2019-05-20')),
|
||
dictGetOrNull('range_key_dictionary', 'value_nullable', number, toDate('2019-05-20')),
|
||
dictGetOrNull('range_key_dictionary', ('value', 'value_nullable'), number, toDate('2019-05-20'))
|
||
FROM system.numbers LIMIT 5 FORMAT TabSeparated;
|
||
```
|
||
Result:
|
||
|
||
``` text
|
||
(0,'2019-05-20') 0 \N \N (NULL,NULL)
|
||
(1,'2019-05-20') 1 First First ('First','First')
|
||
(2,'2019-05-20') 0 \N \N (NULL,NULL)
|
||
(3,'2019-05-20') 0 \N \N (NULL,NULL)
|
||
(4,'2019-05-20') 0 \N \N (NULL,NULL)
|
||
```
|
||
|
||
**See Also**
|
||
|
||
- [External Dictionaries](../../sql-reference/dictionaries/external-dictionaries/external-dicts.md)
|
||
|
||
## dictHas {#dicthas}
|
||
|
||
Checks whether a key is present in a dictionary.
|
||
|
||
``` sql
|
||
dictHas('dict_name', id_expr)
|
||
```
|
||
|
||
**Arguments**
|
||
|
||
- `dict_name` — Name of the dictionary. [String literal](../../sql-reference/syntax.md#syntax-string-literal).
|
||
- `id_expr` — Key value. [Expression](../../sql-reference/syntax.md#syntax-expressions) returning dictionary key-type value or [Tuple](../../sql-reference/data-types/tuple.md)-type value depending on the dictionary configuration.
|
||
|
||
**Returned value**
|
||
|
||
- 0, if there is no key.
|
||
- 1, if there is a key.
|
||
|
||
Type: `UInt8`.
|
||
|
||
## dictGetHierarchy {#dictgethierarchy}
|
||
|
||
Creates an array, containing all the parents of a key in the [hierarchical dictionary](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-hierarchical.md).
|
||
|
||
**Syntax**
|
||
|
||
``` sql
|
||
dictGetHierarchy('dict_name', key)
|
||
```
|
||
|
||
**Arguments**
|
||
|
||
- `dict_name` — Name of the dictionary. [String literal](../../sql-reference/syntax.md#syntax-string-literal).
|
||
- `key` — Key value. [Expression](../../sql-reference/syntax.md#syntax-expressions) returning a [UInt64](../../sql-reference/data-types/int-uint.md)-type value.
|
||
|
||
**Returned value**
|
||
|
||
- Parents for the key.
|
||
|
||
Type: [Array(UInt64)](../../sql-reference/data-types/array.md).
|
||
|
||
## dictIsIn {#dictisin}
|
||
|
||
Checks the ancestor of a key through the whole hierarchical chain in the dictionary.
|
||
|
||
``` sql
|
||
dictIsIn('dict_name', child_id_expr, ancestor_id_expr)
|
||
```
|
||
|
||
**Arguments**
|
||
|
||
- `dict_name` — Name of the dictionary. [String literal](../../sql-reference/syntax.md#syntax-string-literal).
|
||
- `child_id_expr` — Key to be checked. [Expression](../../sql-reference/syntax.md#syntax-expressions) returning a [UInt64](../../sql-reference/data-types/int-uint.md)-type value.
|
||
- `ancestor_id_expr` — Alleged ancestor of the `child_id_expr` key. [Expression](../../sql-reference/syntax.md#syntax-expressions) returning a [UInt64](../../sql-reference/data-types/int-uint.md)-type value.
|
||
|
||
**Returned value**
|
||
|
||
- 0, if `child_id_expr` is not a child of `ancestor_id_expr`.
|
||
- 1, if `child_id_expr` is a child of `ancestor_id_expr` or if `child_id_expr` is an `ancestor_id_expr`.
|
||
|
||
Type: `UInt8`.
|
||
|
||
## dictGetChildren {#dictgetchildren}
|
||
|
||
Returns first-level children as an array of indexes. It is the inverse transformation for [dictGetHierarchy](#dictgethierarchy).
|
||
|
||
**Syntax**
|
||
|
||
``` sql
|
||
dictGetChildren(dict_name, key)
|
||
```
|
||
|
||
**Arguments**
|
||
|
||
- `dict_name` — Name of the dictionary. [String literal](../../sql-reference/syntax.md#syntax-string-literal).
|
||
- `key` — Key value. [Expression](../../sql-reference/syntax.md#syntax-expressions) returning a [UInt64](../../sql-reference/data-types/int-uint.md)-type value.
|
||
|
||
**Returned values**
|
||
|
||
- First-level descendants for the key.
|
||
|
||
Type: [Array](../../sql-reference/data-types/array.md)([UInt64](../../sql-reference/data-types/int-uint.md)).
|
||
|
||
**Example**
|
||
|
||
Consider the hierarchic dictionary:
|
||
|
||
``` text
|
||
┌─id─┬─parent_id─┐
|
||
│ 1 │ 0 │
|
||
│ 2 │ 1 │
|
||
│ 3 │ 1 │
|
||
│ 4 │ 2 │
|
||
└────┴───────────┘
|
||
```
|
||
|
||
First-level children:
|
||
|
||
``` sql
|
||
SELECT dictGetChildren('hierarchy_flat_dictionary', number) FROM system.numbers LIMIT 4;
|
||
```
|
||
|
||
``` text
|
||
┌─dictGetChildren('hierarchy_flat_dictionary', number)─┐
|
||
│ [1] │
|
||
│ [2,3] │
|
||
│ [4] │
|
||
│ [] │
|
||
└──────────────────────────────────────────────────────┘
|
||
```
|
||
|
||
## dictGetDescendant {#dictgetdescendant}
|
||
|
||
Returns all descendants as if [dictGetChildren](#dictgetchildren) function was applied `level` times recursively.
|
||
|
||
**Syntax**
|
||
|
||
``` sql
|
||
dictGetDescendants(dict_name, key, level)
|
||
```
|
||
|
||
**Arguments**
|
||
|
||
- `dict_name` — Name of the dictionary. [String literal](../../sql-reference/syntax.md#syntax-string-literal).
|
||
- `key` — Key value. [Expression](../../sql-reference/syntax.md#syntax-expressions) returning a [UInt64](../../sql-reference/data-types/int-uint.md)-type value.
|
||
- `level` — Hierarchy level. If `level = 0` returns all descendants to the end. [UInt8](../../sql-reference/data-types/int-uint.md).
|
||
|
||
**Returned values**
|
||
|
||
- Descendants for the key.
|
||
|
||
Type: [Array](../../sql-reference/data-types/array.md)([UInt64](../../sql-reference/data-types/int-uint.md)).
|
||
|
||
**Example**
|
||
|
||
Consider the hierarchic dictionary:
|
||
|
||
``` text
|
||
┌─id─┬─parent_id─┐
|
||
│ 1 │ 0 │
|
||
│ 2 │ 1 │
|
||
│ 3 │ 1 │
|
||
│ 4 │ 2 │
|
||
└────┴───────────┘
|
||
```
|
||
All descendants:
|
||
|
||
``` sql
|
||
SELECT dictGetDescendants('hierarchy_flat_dictionary', number) FROM system.numbers LIMIT 4;
|
||
```
|
||
|
||
``` text
|
||
┌─dictGetDescendants('hierarchy_flat_dictionary', number)─┐
|
||
│ [1,2,3,4] │
|
||
│ [2,3,4] │
|
||
│ [4] │
|
||
│ [] │
|
||
└─────────────────────────────────────────────────────────┘
|
||
```
|
||
|
||
First-level descendants:
|
||
|
||
``` sql
|
||
SELECT dictGetDescendants('hierarchy_flat_dictionary', number, 1) FROM system.numbers LIMIT 4;
|
||
```
|
||
|
||
``` text
|
||
┌─dictGetDescendants('hierarchy_flat_dictionary', number, 1)─┐
|
||
│ [1] │
|
||
│ [2,3] │
|
||
│ [4] │
|
||
│ [] │
|
||
└────────────────────────────────────────────────────────────┘
|
||
```
|
||
|
||
## Other Functions {#ext_dict_functions-other}
|
||
|
||
ClickHouse supports specialized functions that convert dictionary attribute values to a specific data type regardless of the dictionary configuration.
|
||
|
||
Functions:
|
||
|
||
- `dictGetInt8`, `dictGetInt16`, `dictGetInt32`, `dictGetInt64`
|
||
- `dictGetUInt8`, `dictGetUInt16`, `dictGetUInt32`, `dictGetUInt64`
|
||
- `dictGetFloat32`, `dictGetFloat64`
|
||
- `dictGetDate`
|
||
- `dictGetDateTime`
|
||
- `dictGetUUID`
|
||
- `dictGetString`
|
||
|
||
All these functions have the `OrDefault` modification. For example, `dictGetDateOrDefault`.
|
||
|
||
Syntax:
|
||
|
||
``` sql
|
||
dictGet[Type]('dict_name', 'attr_name', id_expr)
|
||
dictGet[Type]OrDefault('dict_name', 'attr_name', id_expr, default_value_expr)
|
||
```
|
||
|
||
**Arguments**
|
||
|
||
- `dict_name` — Name of the dictionary. [String literal](../../sql-reference/syntax.md#syntax-string-literal).
|
||
- `attr_name` — Name of the column of the dictionary. [String literal](../../sql-reference/syntax.md#syntax-string-literal).
|
||
- `id_expr` — Key value. [Expression](../../sql-reference/syntax.md#syntax-expressions) returning a [UInt64](../../sql-reference/data-types/int-uint.md) or [Tuple](../../sql-reference/data-types/tuple.md)-type value depending on the dictionary configuration.
|
||
- `default_value_expr` — Value returned if the dictionary does not contain a row with the `id_expr` key. [Expression](../../sql-reference/syntax.md#syntax-expressions) returning the value in the data type configured for the `attr_name` attribute.
|
||
|
||
**Returned value**
|
||
|
||
- If ClickHouse parses the attribute successfully in the [attribute’s data type](../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-structure.md#ext_dict_structure-attributes), functions return the value of the dictionary attribute that corresponds to `id_expr`.
|
||
|
||
- If there is no requested `id_expr` in the dictionary then:
|
||
|
||
- `dictGet[Type]` returns the content of the `<null_value>` element specified for the attribute in the dictionary configuration.
|
||
- `dictGet[Type]OrDefault` returns the value passed as the `default_value_expr` parameter.
|
||
|
||
ClickHouse throws an exception if it cannot parse the value of the attribute or the value does not match the attribute data type.
|