mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-22 15:42:02 +00:00
Document the ComplexKeyRangeHashed dictionary
Задокументировал новый словарь.
This commit is contained in:
parent
cfa571cac4
commit
c75d776d04
@ -58,6 +58,7 @@ LAYOUT(LAYOUT_TYPE(param value)) -- layout settings
|
||||
- [direct](#direct)
|
||||
- [range_hashed](#range-hashed)
|
||||
- [complex_key_hashed](#complex-key-hashed)
|
||||
- [complex_key_range_hashed](#complex-key-range-hashed)
|
||||
- [complex_key_cache](#complex-key-cache)
|
||||
- [ssd_cache](#ssd-cache)
|
||||
- [ssd_complex_key_cache](#complex-key-ssd-cache)
|
||||
@ -269,6 +270,28 @@ PRIMARY KEY Abcdef
|
||||
RANGE(MIN StartTimeStamp MAX EndTimeStamp)
|
||||
```
|
||||
|
||||
### complex_key_range_hashed {#complex-key-range-hashed}
|
||||
|
||||
The dictionary is stored in memory in the form of a hash table with an ordered array of ranges and their corresponding values (see [range_hashed](#range-hashed)). This type of storage is for use with composite [keys](../../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-structure.md).
|
||||
|
||||
Example:
|
||||
|
||||
``` sql
|
||||
CREATE DICTIONARY range_dictionary
|
||||
(
|
||||
CountryID UInt64,
|
||||
CountryKey String,
|
||||
StartDate Date,
|
||||
EndDate Date,
|
||||
Tax Float64 DEFAULT 0.2
|
||||
)
|
||||
PRIMARY KEY CountryID, CountryKey
|
||||
SOURCE(CLICKHOUSE(TABLE 'date_table'))
|
||||
LIFETIME(MIN 1 MAX 1000)
|
||||
LAYOUT(COMPLEX_KEY_RANGE_HASHED())
|
||||
RANGE(MIN StartDate MAX EndDate);
|
||||
```
|
||||
|
||||
### cache {#cache}
|
||||
|
||||
The dictionary is stored in a cache that has a fixed number of cells. These cells contain frequently used elements.
|
||||
|
Loading…
Reference in New Issue
Block a user