> ## Documentation Index
> Fetch the complete documentation index at: https://private-7c7dfe99-parallel-read-in-order-multi-part.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# PostgreSQL dictionary source

> Configure PostgreSQL as a dictionary source in ClickHouse.

Example of settings:

<Tabs>
  <Tab title="DDL">
    ```sql theme={null}
    SOURCE(POSTGRESQL(
        port 5432
        host 'postgresql-hostname'
        user 'postgres_user'
        password 'postgres_password'
        db 'db_name'
        table 'table_name'
        replica(host 'example01-1' port 5432 priority 1)
        replica(host 'example01-2' port 5432 priority 2)
        where 'id=10'
        invalidate_query 'SQL_QUERY'
        query 'SELECT id, value_1, value_2 FROM db_name.table_name'
    ))
    ```
  </Tab>

  <Tab title="Configuration file">
    ```xml theme={null}
    <source>
      <postgresql>
          <host>postgresql-hostname</host>
          <port>5432</port>
          <user>clickhouse</user>
          <password>qwerty</password>
          <db>db_name</db>
          <table>table_name</table>
          <where>id=10</where>
          <invalidate_query>SQL_QUERY</invalidate_query>
          <query>SELECT id, value_1, value_2 FROM db_name.table_name</query>
      </postgresql>
    </source>
    ```
  </Tab>
</Tabs>

<br />

Setting fields:

| Setting | Description |
| - | - |
| `host` | The host on the PostgreSQL server. You can specify it for all replicas, or for each one individually (inside `<replica>`). |
| `port` | The port on the PostgreSQL server. You can specify it for all replicas, or for each one individually (inside `<replica>`). |
| `user` | Name of the PostgreSQL user. You can specify it for all replicas, or for each one individually (inside `<replica>`). |
| `password` | Password of the PostgreSQL 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 PostgreSQL host. |
| `replica/port` | The PostgreSQL port. |
| `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. The syntax for conditions is the same as for `WHERE` clause in PostgreSQL. For example, `id > 10 AND id < 20`. Optional. |
| `invalidate_query` | Query for checking the dictionary status. Optional. Read more in the section [Refreshing dictionary data using LIFETIME](/reference/statements/create/dictionary/lifetime). |
| `background_reconnect` | Reconnect to replica in background if connection fails. Optional. |
| `query` | The custom query. Optional. |
| `sslmode` | TLS/SSL mode passed to `libpq`: `disable`, `allow`, `prefer`, `require`, `verify-ca` or `verify-full`. When unset, the `libpq` default of `prefer` applies. Optional. |
| `sslrootcert_pem` | Contents of the CA certificate that the PostgreSQL server certificate is verified against. Optional. |
| `sslcert_pem` | Contents of the client certificate, for certificate-based authentication. Optional. |
| `sslkey_pem` | Contents of the private key belonging to `sslcert_pem`. Optional. |
| `sslrootcert`, `sslcert`, `sslkey` | The same credentials as paths to files on the server. Only allowed for a dictionary defined in a server configuration file, or through a named collection defined there, see below. Optional. |

<Note>
  The `table` or `where` fields cannot be used together with the `query` field. And either one of the `table` or `query` fields must be declared.
</Note>

<Note>
  `sslrootcert`, `sslcert` and `sslkey` name files that the server opens with its own privileges, so they are only accepted for a dictionary defined in a server configuration file, or through a named collection defined there. A dictionary created with a `CREATE DICTIONARY` query must pass the contents instead, in `sslrootcert_pem`, `sslcert_pem` and `sslkey_pem`. Those values are masked in logs and in `SHOW` queries, the same way passwords are.
</Note>