ClickHouse/docs/en/query_language/dicts/external_dicts_dict_sources.md

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# Sources of External Dictionaries {#dicts-external_dicts_dict_sources}
An external dictionary can be connected from many different sources.
The configuration looks like this:
```xml
<yandex>
<dictionary>
...
<source>
<source_type>
<!-- Source configuration -->
</source_type>
</source>
...
</dictionary>
...
</yandex>
```
The source is configured in the `source` section.
Types of sources (`source_type`):
- [Local file](#dicts-external_dicts_dict_sources-local_file)
- [Executable file](#dicts-external_dicts_dict_sources-executable)
- [HTTP(s)](#dicts-external_dicts_dict_sources-http)
- DBMS
- [MySQL](#dicts-external_dicts_dict_sources-mysql)
- [ClickHouse](#dicts-external_dicts_dict_sources-clickhouse)
- [MongoDB](#dicts-external_dicts_dict_sources-mongodb)
- [ODBC](#dicts-external_dicts_dict_sources-odbc)
## Local File {#dicts-external_dicts_dict_sources-local_file}
Example of settings:
```xml
<source>
<file>
<path>/opt/dictionaries/os.tsv</path>
<format>TabSeparated</format>
</file>
</source>
```
Setting fields:
- `path` The absolute path to the file.
- `format` The file format. All the formats described in "[Formats](../../interfaces/formats.md#formats)" are supported.
## Executable File {#dicts-external_dicts_dict_sources-executable}
Working with executable files depends on [how the dictionary is stored in memory](external_dicts_dict_layout.md). If the dictionary is stored using `cache` and `complex_key_cache`, ClickHouse requests the necessary keys by sending a request to the executable file's `STDIN`.
Example of settings:
```xml
<source>
<executable>
<command>cat /opt/dictionaries/os.tsv</command>
<format>TabSeparated</format>
</executable>
</source>
```
Setting fields:
- `command` The absolute path to the executable file, or the file name (if the program directory is written to `PATH`).
- `format` The file format. All the formats described in "[Formats](../../interfaces/formats.md#formats)" are supported.
## HTTP(s) {#dicts-external_dicts_dict_sources-http}
Working with an HTTP(s) server depends on [how the dictionary is stored in memory](external_dicts_dict_layout.md). If the dictionary is stored using `cache` and `complex_key_cache`, ClickHouse requests the necessary keys by sending a request via the `POST` method.
Example of settings:
```xml
<source>
<http>
<url>http://[::1]/os.tsv</url>
<format>TabSeparated</format>
</http>
</source>
```
In order for ClickHouse to access an HTTPS resource, you must [configure openSSL](../../operations/server_settings/settings.md#server_settings-openssl) in the server configuration.
Setting fields:
- `url` The source URL.
- `format` The file format. All the formats described in "[Formats](../../interfaces/formats.md#formats)" are supported.
## ODBC {#dicts-external_dicts_dict_sources-odbc}
You can use this method to connect any database that has an ODBC driver.
Example of settings:
```xml
<odbc>
<db>DatabaseName</db>
<table>ShemaName.TableName</table>
<connection_string>DSN=some_parameters</connection_string>
<invalidate_query>SQL_QUERY</invalidate_query>
</odbc>
```
Setting fields:
- `db` Name of the database. Omit it if the database name is set in the `<connection_string>` parameters.
- `table` Name of the table and schema if exists.
- `connection_string` Connection string.
- `invalidate_query` Query for checking the dictionary status. Optional parameter. Read more in the section [Updating dictionaries](external_dicts_dict_lifetime.md).
ClickHouse receives quoting symbols from ODBC-driver and quote all settings in queries to driver, so it's necessary to set table name accordingly to table name case in database.
If you have a problems with encodings when using Oracle, see the corresponding [FAQ](../../faq/general.md#oracle-odbc-encodings) article.
### Known vulnerability of the ODBC dictionary functionality
!!! attention
When connecting to the database through the ODBC driver connection parameter `Servername` can be substituted. In this case values of `USERNAME` and `PASSWORD` from `odbc.ini` are sent to the remote server and can be compromised.
**Example of insecure use**
Let's configure unixODBC for PostgreSQL. Content of `/etc/odbc.ini`:
```
[gregtest]
Driver = /usr/lib/psqlodbca.so
Servername = localhost
PORT = 5432
DATABASE = test_db
#OPTION = 3
USERNAME = test
PASSWORD = test
```
If you then make a query such as
```
SELECT * FROM odbc('DSN=gregtest;Servername=some-server.com', 'test_db');
```
ODBC driver will send values of `USERNAME` and `PASSWORD` from `odbc.ini` to `some-server.com`.
### Example of Connecting PostgreSQL
Ubuntu OS.
Installing unixODBC and the ODBC driver for PostgreSQL:
sudo apt-get install -y unixodbc odbcinst odbc-postgresql
Configuring `/etc/odbc.ini` (or `~/.odbc.ini`):
```
[DEFAULT]
Driver = myconnection
[myconnection]
Description = PostgreSQL connection to my_db
Driver = PostgreSQL Unicode
Database = my_db
Servername = 127.0.0.1
UserName = username
Password = password
Port = 5432
Protocol = 9.3
ReadOnly = No
RowVersioning = No
ShowSystemTables = No
ConnSettings =
```
The dictionary configuration in ClickHouse:
```xml
<yandex>
<dictionary>
<name>table_name</name>
<source>
<odbc>
<!-- You can specify the following parameters in connection_string: -->
<!-- DSN=myconnection;UID=username;PWD=password;HOST=127.0.0.1;PORT=5432;DATABASE=my_db -->
<connection_string>DSN=myconnection</connection_string>
<table>postgresql_table</table>
</odbc>
</source>
<lifetime>
<min>300</min>
<max>360</max>
</lifetime>
<layout>
<hashed/>
</layout>
<structure>
<id>
<name>id</name>
</id>
<attribute>
<name>some_column</name>
<type>UInt64</type>
<null_value>0</null_value>
</attribute>
</structure>
</dictionary>
</yandex>
```
You may need to edit `odbc.ini` to specify the full path to the library with the driver `DRIVER=/usr/local/lib/psqlodbcw.so`.
### Example of Connecting MS SQL Server
Ubuntu OS.
Installing the driver: :
```
sudo apt-get install tdsodbc freetds-bin sqsh
```
Configuring the driver: :
```
$ cat /etc/freetds/freetds.conf
...
[MSSQL]
host = 192.168.56.101
port = 1433
tds version = 7.0
client charset = UTF-8
$ cat /etc/odbcinst.ini
...
[FreeTDS]
Description = FreeTDS
Driver = /usr/lib/x86_64-linux-gnu/odbc/libtdsodbc.so
Setup = /usr/lib/x86_64-linux-gnu/odbc/libtdsS.so
FileUsage = 1
UsageCount = 5
$ cat ~/.odbc.ini
...
[MSSQL]
Description = FreeTDS
Driver = FreeTDS
Servername = MSSQL
Database = test
UID = test
PWD = test
Port = 1433
```
Configuring the dictionary in ClickHouse:
```xml
<yandex>
<dictionary>
<name>test</name>
<source>
<odbc>
<table>dict</table>
<connection_string>DSN=MSSQL;UID=test;PWD=test</connection_string>
</odbc>
</source>
<lifetime>
<min>300</min>
<max>360</max>
</lifetime>
<layout>
<flat />
</layout>
<structure>
<id>
<name>k</name>
</id>
<attribute>
<name>s</name>
<type>String</type>
<null_value></null_value>
</attribute>
</structure>
</dictionary>
</yandex>
```
## DBMS
### MySQL {#dicts-external_dicts_dict_sources-mysql}
Example of settings:
```xml
<source>
<mysql>
<port>3306</port>
<user>clickhouse</user>
<password>qwerty</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>
</source>
```
Setting fields:
- `port` The port on the MySQL server. You can specify it for all replicas, or for each one individually (inside `<replica>`).
- `user` Name of the MySQL user. You can specify it for all replicas, or for each one individually (inside `<replica>`).
- `password` Password of the MySQL user. You can specify it for all replicas, or for each one individually (inside `<replica>`).
- `replica` Section of replica configurations. There can be multiple sections.
- `replica/host` The MySQL host.
\* `replica/priority` The replica priority. When attempting to connect, ClickHouse traverses the replicas in order of priority. The lower the number, the higher the priority.
- `db` Name of the database.
- `table` Name of the table.
- `where ` The selection criteria. Optional parameter.
- `invalidate_query` Query for checking the dictionary status. Optional parameter. Read more in the section [Updating dictionaries](external_dicts_dict_lifetime.md).
MySQL can be connected on a local host via sockets. To do this, set `host` and `socket`.
Example of settings:
```xml
<source>
<mysql>
<host>localhost</host>
<socket>/path/to/socket/file.sock</socket>
<user>clickhouse</user>
<password>qwerty</password>
<db>db_name</db>
<table>table_name</table>
<where>id=10</where>
<invalidate_query>SQL_QUERY</invalidate_query>
</mysql>
</source>
```
### ClickHouse {#dicts-external_dicts_dict_sources-clickhouse}
Example of settings:
```xml
<source>
<clickhouse>
<host>example01-01-1</host>
<port>9000</port>
<user>default</user>
<password></password>
<db>default</db>
<table>ids</table>
<where>id=10</where>
</clickhouse>
</source>
```
Setting fields:
- `host` The ClickHouse host. If it is a local host, the query is processed without any network activity. To improve fault tolerance, you can create a [Distributed](../../operations/table_engines/distributed.md) table and enter it in subsequent configurations.
- `port` The port on the ClickHouse server.
- `user` Name of the ClickHouse user.
- `password` Password of the ClickHouse user.
- `db` Name of the database.
- `table` Name of the table.
- `where ` The selection criteria. May be omitted.
- `invalidate_query` Query for checking the dictionary status. Optional parameter. Read more in the section [Updating dictionaries](external_dicts_dict_lifetime.md).
### MongoDB {#dicts-external_dicts_dict_sources-mongodb}
Example of settings:
```xml
<source>
<mongodb>
<host>localhost</host>
<port>27017</port>
<user></user>
<password></password>
<db>test</db>
<collection>dictionary_source</collection>
</mongodb>
</source>
```
Setting fields:
- `host` The MongoDB host.
- `port` The port on the MongoDB server.
- `user` Name of the MongoDB user.
- `password` Password of the MongoDB user.
- `db` Name of the database.
- `collection` Name of the collection.
[Original article](https://clickhouse.yandex/docs/en/query_language/dicts/external_dicts_dict_sources/) <!--hide-->