Functions for Working with Embedded Dictionaries

:::note In order for the functions below to work, the server config must specify the paths and addresses for getting all the embedded dictionaries. The dictionaries are loaded at the first call of any of these functions. If the reference lists can't be loaded, an exception is thrown.

As such, the examples shown in this section will throw an exception in ClickHouse Fiddle and in quick release and production deployments by default, unless first configured. :::

For information about creating reference lists, see the section "Dictionaries".

Multiple Geobases {#multiple-geobases}

ClickHouse supports working with multiple alternative geobases (regional hierarchies) simultaneously, in order to support various perspectives on which countries certain regions belong to.

The 'clickhouse-server' config specifies the file with the regional hierarchy:

<path_to_regions_hierarchy_file>/opt/geo/regions_hierarchy.txt</path_to_regions_hierarchy_file>

Besides this file, it also searches for files nearby that have the _ symbol and any suffix appended to the name (before the file extension). For example, it will also find the file /opt/geo/regions_hierarchy_ua.txt, if present. Here ua is called the dictionary key. For a dictionary without a suffix, the key is an empty string.

All the dictionaries are re-loaded during runtime (once every certain number of seconds, as defined in the builtin_dictionaries_reload_interval config parameter, or once an hour by default). However, the list of available dictionaries is defined once, when the server starts.

All functions for working with regions have an optional argument at the end – the dictionary key. It is referred to as the geobase.

Example:

sql

regionToCountry(RegionID) – Uses the default dictionary: /opt/geo/regions_hierarchy.txt
regionToCountry(RegionID, '') – Uses the default dictionary: /opt/geo/regions_hierarchy.txt
regionToCountry(RegionID, 'ua') – Uses the dictionary for the 'ua' key: /opt/geo/regions_hierarchy_ua.txt

regionToName {#regiontoname}

Accepts a region ID and geobase and returns a string of the name of the region in the corresponding language. If the region with the specified ID does not exist, an empty string is returned.

Syntax

sql

regionToName(id\[, lang\])

Parameters

id — Region ID from the geobase. UInt32.
geobase — Dictionary key. See Multiple Geobases. String. Optional.

Returned value

Name of the region in the corresponding language specified by geobase. String.
Otherwise, an empty string.

Example

Query:

sql

SELECT regionToName(number::UInt32,'en') FROM numbers(0,5);

Result:

text

┌─regionToName(CAST(number, 'UInt32'), 'en')─┐
│                                            │
│ World                                      │
│ USA                                        │
│ Colorado                                   │
│ Boulder County                             │
└────────────────────────────────────────────┘

regionToCity {#regiontocity}

Accepts a region ID from the geobase. If this region is a city or part of a city, it returns the region ID for the appropriate city. Otherwise, returns 0.

Syntax

sql

regionToCity(id [, geobase])

Parameters

id — Region ID from the geobase. UInt32.
geobase — Dictionary key. See Multiple Geobases. String. Optional.

Returned value

Region ID for the appropriate city, if it exists. UInt32.
0, if there is none.

Example

Query:

sql

SELECT regionToName(number::UInt32, 'en'), regionToCity(number::UInt32) AS id, regionToName(id, 'en') FROM numbers(13);

Result:

response

┌─regionToName(CAST(number, 'UInt32'), 'en')─┬─id─┬─regionToName(regionToCity(CAST(number, 'UInt32')), 'en')─┐
│                                            │  0 │                                                          │
│ World                                      │  0 │                                                          │
│ USA                                        │  0 │                                                          │
│ Colorado                                   │  0 │                                                          │
│ Boulder County                             │  0 │                                                          │
│ Boulder                                    │  5 │ Boulder                                                  │
│ China                                      │  0 │                                                          │
│ Sichuan                                    │  0 │                                                          │
│ Chengdu                                    │  8 │ Chengdu                                                  │
│ America                                    │  0 │                                                          │
│ North America                              │  0 │                                                          │
│ Eurasia                                    │  0 │                                                          │
│ Asia                                       │  0 │                                                          │
└────────────────────────────────────────────┴────┴──────────────────────────────────────────────────────────┘

regionToArea {#regiontoarea}

Converts a region to an area (type 5 in the geobase). In every other way, this function is the same as 'regionToCity'.

Syntax

sql

regionToArea(id [, geobase])

Parameters

id — Region ID from the geobase. UInt32.
geobase — Dictionary key. See Multiple Geobases. String. Optional.

Returned value

Region ID for the appropriate area, if it exists. UInt32.
0, if there is none.

Example

Query:

sql

SELECT DISTINCT regionToName(regionToArea(toUInt32(number), 'ua'))
FROM system.numbers
LIMIT 15

Result:

text

┌─regionToName(regionToArea(toUInt32(number), \'ua\'))─┐
│                                                      │
│ Moscow and Moscow region                             │
│ St. Petersburg and Leningrad region                  │
│ Belgorod region                                      │
│ Ivanovsk region                                      │
│ Kaluga region                                        │
│ Kostroma region                                      │
│ Kursk region                                         │
│ Lipetsk region                                       │
│ Orlov region                                         │
│ Ryazan region                                        │
│ Smolensk region                                      │
│ Tambov region                                        │
│ Tver region                                          │
│ Tula region                                          │
└──────────────────────────────────────────────────────┘

regionToDistrict {#regiontodistrict}

Converts a region to a federal district (type 4 in the geobase). In every other way, this function is the same as 'regionToCity'.

Syntax

sql

regionToDistrict(id [, geobase])

Parameters

id — Region ID from the geobase. UInt32.
geobase — Dictionary key. See Multiple Geobases. String. Optional.

Returned value

Region ID for the appropriate city, if it exists. UInt32.
0, if there is none.

Example

Query:

sql

SELECT DISTINCT regionToName(regionToDistrict(toUInt32(number), 'ua'))
FROM system.numbers
LIMIT 15

Result:

text

┌─regionToName(regionToDistrict(toUInt32(number), \'ua\'))─┐
│                                                          │
│ Central federal district                                 │
│ Northwest federal district                               │
│ South federal district                                   │
│ North Caucases federal district                          │
│ Privolga federal district                                │
│ Ural federal district                                    │
│ Siberian federal district                                │
│ Far East federal district                                │
│ Scotland                                                 │
│ Faroe Islands                                            │
│ Flemish region                                           │
│ Brussels capital region                                  │
│ Wallonia                                                 │
│ Federation of Bosnia and Herzegovina                     │
└──────────────────────────────────────────────────────────┘

regionToCountry {#regiontocountry}

Converts a region to a country (type 3 in the geobase). In every other way, this function is the same as 'regionToCity'.

Syntax

sql

regionToCountry(id [, geobase])

Parameters

id — Region ID from the geobase. UInt32.
geobase — Dictionary key. See Multiple Geobases. String. Optional.

Returned value

Region ID for the appropriate country, if it exists. UInt32.
0, if there is none.

Example

Query:

sql

SELECT regionToName(number::UInt32, 'en'), regionToCountry(number::UInt32) AS id, regionToName(id, 'en') FROM numbers(13);

Result:

text

┌─regionToName(CAST(number, 'UInt32'), 'en')─┬─id─┬─regionToName(regionToCountry(CAST(number, 'UInt32')), 'en')─┐
│                                            │  0 │                                                             │
│ World                                      │  0 │                                                             │
│ USA                                        │  2 │ USA                                                         │
│ Colorado                                   │  2 │ USA                                                         │
│ Boulder County                             │  2 │ USA                                                         │
│ Boulder                                    │  2 │ USA                                                         │
│ China                                      │  6 │ China                                                       │
│ Sichuan                                    │  6 │ China                                                       │
│ Chengdu                                    │  6 │ China                                                       │
│ America                                    │  0 │                                                             │
│ North America                              │  0 │                                                             │
│ Eurasia                                    │  0 │                                                             │
│ Asia                                       │  0 │                                                             │
└────────────────────────────────────────────┴────┴─────────────────────────────────────────────────────────────┘

regionToContinent {#regiontocontinent}

Converts a region to a continent (type 1 in the geobase). In every other way, this function is the same as 'regionToCity'.

Syntax

sql

regionToContinent(id [, geobase])

Parameters

id — Region ID from the geobase. UInt32.
geobase — Dictionary key. See Multiple Geobases. String. Optional.

Returned value

Region ID for the appropriate continent, if it exists. UInt32.
0, if there is none.

Example

Query:

sql

SELECT regionToName(number::UInt32, 'en'), regionToContinent(number::UInt32) AS id, regionToName(id, 'en') FROM numbers(13);

Result:

text

┌─regionToName(CAST(number, 'UInt32'), 'en')─┬─id─┬─regionToName(regionToContinent(CAST(number, 'UInt32')), 'en')─┐
│                                            │  0 │                                                               │
│ World                                      │  0 │                                                               │
│ USA                                        │ 10 │ North America                                                 │
│ Colorado                                   │ 10 │ North America                                                 │
│ Boulder County                             │ 10 │ North America                                                 │
│ Boulder                                    │ 10 │ North America                                                 │
│ China                                      │ 12 │ Asia                                                          │
│ Sichuan                                    │ 12 │ Asia                                                          │
│ Chengdu                                    │ 12 │ Asia                                                          │
│ America                                    │  9 │ America                                                       │
│ North America                              │ 10 │ North America                                                 │
│ Eurasia                                    │ 11 │ Eurasia                                                       │
│ Asia                                       │ 12 │ Asia                                                          │
└────────────────────────────────────────────┴────┴───────────────────────────────────────────────────────────────┘

regionToTopContinent {#regiontotopcontinent}

Finds the highest continent in the hierarchy for the region.

Syntax

sql

regionToTopContinent(id[, geobase])

Parameters

id — Region ID from the geobase. UInt32.
geobase — Dictionary key. See Multiple Geobases. String. Optional.

Returned value

Identifier of the top level continent (the latter when you climb the hierarchy of regions).UInt32.
0, if there is none.

Example

Query:

sql

SELECT regionToName(number::UInt32, 'en'), regionToTopContinent(number::UInt32) AS id, regionToName(id, 'en') FROM numbers(13);

Result:

text

┌─regionToName(CAST(number, 'UInt32'), 'en')─┬─id─┬─regionToName(regionToTopContinent(CAST(number, 'UInt32')), 'en')─┐
│                                            │  0 │                                                                  │
│ World                                      │  0 │                                                                  │
│ USA                                        │  9 │ America                                                          │
│ Colorado                                   │  9 │ America                                                          │
│ Boulder County                             │  9 │ America                                                          │
│ Boulder                                    │  9 │ America                                                          │
│ China                                      │ 11 │ Eurasia                                                          │
│ Sichuan                                    │ 11 │ Eurasia                                                          │
│ Chengdu                                    │ 11 │ Eurasia                                                          │
│ America                                    │  9 │ America                                                          │
│ North America                              │  9 │ America                                                          │
│ Eurasia                                    │ 11 │ Eurasia                                                          │
│ Asia                                       │ 11 │ Eurasia                                                          │
└────────────────────────────────────────────┴────┴──────────────────────────────────────────────────────────────────┘

regionToPopulation {#regiontopopulation}

Gets the population for a region. The population can be recorded in files with the geobase. See the section "Dictionaries". If the population is not recorded for the region, it returns 0. In the geobase, the population might be recorded for child regions, but not for parent regions.

Syntax

sql

regionToPopulation(id[, geobase])

Parameters

id — Region ID from the geobase. UInt32.
geobase — Dictionary key. See Multiple Geobases. String. Optional.

Returned value

Population for the region. UInt32.
0, if there is none.

Example

Query:

sql

SELECT regionToName(number::UInt32, 'en'), regionToPopulation(number::UInt32) AS id, regionToName(id, 'en') FROM numbers(13);

Result:

text

┌─regionToName(CAST(number, 'UInt32'), 'en')─┬─population─┐
│                                            │          0 │
│ World                                      │ 4294967295 │
│ USA                                        │  330000000 │
│ Colorado                                   │    5700000 │
│ Boulder County                             │     330000 │
│ Boulder                                    │     100000 │
│ China                                      │ 1500000000 │
│ Sichuan                                    │   83000000 │
│ Chengdu                                    │   20000000 │
│ America                                    │ 1000000000 │
│ North America                              │  600000000 │
│ Eurasia                                    │ 4294967295 │
│ Asia                                       │ 4294967295 │
└────────────────────────────────────────────┴────────────┘

regionIn {#regionin}

Checks whether a lhs region belongs to a rhs region. Returns a UInt8 number equal to 1 if it belongs, or 0 if it does not belong.

Syntax

sql

regionIn(lhs, rhs\[, geobase\])

Parameters

lhs — Lhs region ID from the geobase. UInt32.
rhs — Rhs region ID from the geobase. UInt32.
geobase — Dictionary key. See Multiple Geobases. String. Optional.

Returned value

1, if it belongs. UInt8.
0, if it doesn't belong.

Implementation details

The relationship is reflexive – any region also belongs to itself.

Example

Query:

sql

SELECT regionToName(n1.number::UInt32, 'en') || (regionIn(n1.number::UInt32, n2.number::UInt32) ? ' is in ' : ' is not in ') || regionToName(n2.number::UInt32, 'en') FROM numbers(1,2) AS n1 CROSS JOIN numbers(1,5) AS n2;

Result:

text

World is in World
World is not in USA
World is not in Colorado
World is not in Boulder County
World is not in Boulder
USA is in World
USA is in USA
USA is not in Colorado
USA is not in Boulder County
USA is not in Boulder

regionHierarchy {#regionhierarchy}

Accepts a UInt32 number – the region ID from the geobase. Returns an array of region IDs consisting of the passed region and all parents along the chain.

Syntax

sql

regionHierarchy(id\[, geobase\])

Parameters

id — Region ID from the geobase. UInt32.
geobase — Dictionary key. See Multiple Geobases. String. Optional.

Returned value

Array of region IDs consisting of the passed region and all parents along the chain. Array(UInt32).

Example

Query:

sql

SELECT regionHierarchy(number::UInt32) AS arr, arrayMap(id -> regionToName(id, 'en'), arr) FROM numbers(5);

Result:

text

┌─arr────────────┬─arrayMap(lambda(tuple(id), regionToName(id, 'en')), regionHierarchy(CAST(number, 'UInt32')))─┐
│ []             │ []                                                                                           │
│ [1]            │ ['World']                                                                                    │
│ [2,10,9,1]     │ ['USA','North America','America','World']                                                    │
│ [3,2,10,9,1]   │ ['Colorado','USA','North America','America','World']                                         │
│ [4,3,2,10,9,1] │ ['Boulder County','Colorado','USA','North America','America','World']                        │
└────────────────┴──────────────────────────────────────────────────────────────────────────────────────────────┘