如果您已经打开了门文章，那么确保您已经使用ClickHouse，并且您会错过有关它的便利性和速度的有趣细节，并且直截了当-实际上，如何在ClickHouse中创建字典并使用它们。

ClickHouse中的词典是什么？

— key → value. ClickHouse, ETL- .

ClickHouse :

ClickHouse .
TTL – ClickHouse .
ClickHouse — XML- DDL-.

: / , HTTP(s) , ..

xml-, dictionaries_config ClickHouse.

, dictionaries_lazy_load.

( ) — .

, , system.dictionaries, :

;
;
, RAM .

xml DDL-. , — DDL-.

xml :

<yandex>
    <!-- ,   -->
    <comment>Some comments</comment>

    <!-- ,    -->
    <include_from>/etc/metrika.xml</include_from>

    <dictionary>
        <!--   -->
    </dictionary>

    ...

    <dictionary>
        <!--   -->
    </dictionary>
</yandex>

DDL-, .

<dictionary>
    <name>clients</name>
    <surce>
        <clickhouse>
            <host>myHostName</host>
            <port>9000</port>
            <user>admin</user>
            <password>secret_password</password>
            <db>clients</db>
            <table>users</table>
            <where>id<=10</where>
        </clickhouse>
    </surce>
    <lifetime>
        <min>3600</min>
        <max>5400</max>
    </lifetime>
    <layout>
        <flat/>
    </layout>
    <structure>
        <id>user_id</id>
        <attribute>
            <name>username</name>
            <type>string</type>
        </attribute>
        <attribute>
            <name>age</name>
            <type>Int8</type>
        </attribute>
    </structure>
</dictionary>

name — ;
source — ;
lifetime — ;
layout — . ;
structure — . , .

DDL-:

CREATE DICTIONARY dict_users_id (
    id UInt64,
    username String,
    email String,
    status UInt16,
    hash String
)
PRIMARY KEY id
SOURCE(MYSQL(
    port 3306
    user clickhouse
    password secret_password
    replica(host 'mysql1.fevlake.com' priority 1)
    db fevlake_dicts
    table users
))
LAYOUT(HASHED())
LIFETIME(MIN 3600 MAX 5400);

. — :

HTTP(s)

— , .

<surce>
    <file>
      <path>/opt/dictionaries/clients.csv</path>
      <format>CSV</format>
    </file>
</surce>

path — .
format — . ClickHouse.

DDL-:

SOURCE(FILE(path '/opt/dictionaries/clients.csv' format 'CSV'))
SETTINGS(format_csv_allow_single_quotes = 0)

MySQL .

<surce>
    <mysql>
        <port>3306</port>
        <user>clickhouse</user>
        <password>secret_password</password>
        <replica>
            <host>example01-1</host>
            <priority>1</priority>
        </replica>
        <replica>
            <host>example01-2</host>
            <priority>1</priority>
        </replica>
        <db>db_name</db>
        <table>table_name</table>
        <where>id=10</where>
        <invalidate_query>SQL_QUERY</invalidate_query>
    </mysql>
</surce>

port — MySQL. <replica>.
user — MySQL. <replica>.
password — MySQL. <replica>.
replica — . .
db — .
table — .
where — . WHERE MySQL, , id >= 3 AND id < 10 ( ).
invalidate_query — ( ).

DDL-:

SOURCE(MYSQL(
    port 3306
    user clickhouse
    password secret_password
    replica(host 'mysql1.fevlake.com' priority 1)
    db fevlake_dicts
    table users
))

ClickHouse:

flat
hashed
sparse_hashed
cache
direct
range_hashed
complex_key_hashed
complex_key_cache
complex_key_direct
ip_trie

3, , — flat, hashed complex_key_hashed. .

Flat

, . UInt64 500 000, ClickHouse .

<layout>
    <flat/>
</layout>

LAYOUT(FLAT())

Hashed

- . , .

<layout>
    <hashed/>
</layout>

LAYOUT(HASHED())

omplex_key_hashed

. hashed .

<layout>
    <hashed/>
</layout>

LAYOUT(COMPLEX_KEY_HASHED())

<structure> , .

XML:

<structure>
    <id>user_id</id>
    <attribute>
        <name>username</name>
        <type>string</type>
    </attribute>
    <attribute>
        <name>age</name>
        <type>Int8</type>
    </attribute>
</structure>

<id> — ;
<attribute> — . .

ClickHouse :

. UInt64. <id> PRIMARY KEY.
. . <key> PRIMARY KEY.

: UInt64.

<id>
    <name>user_id</name>
</id>

CREATE DICTIONARY (
    user_id UInt64,
    ...
)
PRIMARY KEY user_id
...

PRIMARY KEY – .

(tuple) . layout complex_key_hashed complex_key_cache.

<key>. , . :

<key>
    <attribute>
        <name>field1</name>
        <type>String</type>
    </attribute>
    <attrbute>
        <name>field2</name>
        <type>UInt32</type>
    </attribute>
    ...
</key>

CREATE DICTIONARY ( field1 String, field2 String ... )
PRIMARY KEY field1, field2
...

<structure>
    ...
    <attribute>
        <name>Name</name>
        <type>ClickHouseDataType</type>
        <null_value></null_value>
        <expression>rand64()</expression>
        <hierarchical>true</hierarchical>
        <injective>true</injective>
        <is_object_id>true</is_object_id>
    </attribute>
</structure>

CREATE DICTIONARY somename (
    Name ClickHouseDataType DEFAULT '' EXPRESSION rand64() HIERARCHICAL INJECTIVE IS_OBJECT_ID
)

ClickHouse

ClickHouse — IP (v4) .

, : ip String country String. GeoIP2 MaxMind.

MaxMind .mmdb API .

ClickHouse .mmdb, – MaxMind CSV, .

IP , :

GeoIP2-Country-Blocks-IPv4.csv – IP ID ;
GeoIP2-Country-Locations-en.csv – .

, DDL:

CREATE DICTIONARY dicts.geoip_country_blocks_ipv4 (
    network String DEFAULT '',
    geoname_id UInt64 DEFAULT 0,
    registered_country_geoname_id UInt64 DEFAULT 0,
    represented_country_geoname_id UInt64 DEFAULT 0,
    is_anonymous_proxy UInt8 DEFAULT 0,
    is_satellite_provider UInt8 DEFAULT 0
) 
PRIMARY KEY network
SOURCE(FILE(
    path '/var/lib/clickhouse/user_files/GeoIP2-Country-Blocks-IPv4.csv'
    format 'CSVWithNames'
))
LAYOUT(IP_TRIE())
LIFETIME(300);

geoip_country_blocks_ipv4 :

network – IP , .
geoname_id – ID .

– CSV.

ClickHouse ID, ip_trie. IP .

geoip_country_locations_en:

CREATE DICTIONARY dicts.geoip_country_locations_en (
    geoname_id UInt64 DEFAULT 0,
    locale_code String DEFAULT '',
    continent_code String DEFAULT '',
    continent_name String DEFAULT '',
    country_iso_code String DEFAULT '',
    country_name String DEFAULT '',
    is_in_european_union UInt8 DEFAULT 0
)
PRIMARY KEY geoname_id
SOURCE(FILE(
    path '/var/lib/clickhouse/user_files/GeoIP2-Country-Locations-en.csv'
    format 'CSVWithNames'
))
LAYOUT(HASHED())
LIFETIME(300);

ID . GeoIP2-Country-Locations-en.csv :

geoname_id – ID , , .
country_name – .

hashed.

CSV .

, :

CREATE TEMPORARY TABLE user_visits (user_ip String, user_id UUID);
---
INSERT INTO user_visits VALUES
    ('178.248.237.68', generateUUIDv4()),
    ('82.192.95.175', generateUUIDv4());

. – dictGet*:

SELECT 
    dictGetString('dicts.geoip_city_locations_en', 'country_name', users_country_id) AS users_country, 
    uniqs
FROM (
    SELECT 
        dictGetUInt64('dicts.geoip_country_blocks_ipv4', 'geoname_id', tuple(IPv4StringToNum(user_ip))) AS users_country_id, 
        uniq(user_id) AS uniqs
    FROM user_visits
    GROUP BY users_country_id
);

┌─users_country─┬─uniqs─┐
│ Russia        │     1 │
│ Netherlands   │     1 │
└───────────────┴───────┘
2 rows in set. Elapsed: 0.003 sec.

user_ip , ip_trie-: tuple(IPv4StringToNum(user_ip));
, ID users_country_id: dictGetUInt64('geoip_country_blocks_ipv4', 'geoname_id', ...) as users_country_id;
: uniq(user_id) as uniq_users;
ID , : GROUP BY users_country_id;
, ID , : dictGetString('geoip_city_locations_en', 'country_name', users_country_id) AS users_country.

. GeoIP2 , :)

. , ClickHouse .

如何在ClickHouse中创建和使用词典

ClickHouse中的词典是什么？

Flat

Hashed

omplex_key_hashed

ClickHouse

More articles: