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You use foreign data wrappers (FDWs) to query external data sources from a . These external data sources can be one of the following:
  • Other s
  • databases outside of
If you are using peering, you can create FDWs in your Customer VPC to query a in your project. However, you can’t create FDWs in your s to query a data source in your Customer VPC. This is because peering uses AWS PrivateLink for increased security. See VPC peering documentation for additional details. FDWs are particularly useful if you manage multiple s with different capabilities, and need to seamlessly access and merge regular and time-series data.

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Prerequisites

To follow the steps on this page:
  • Create a target with the Real-time analytics capability enabled.

     You need your connection details. This procedure also works for .

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Query another data source

To query another data source:
You create FDWs with the postgres_fdw extension, which is enabled by default in .
  1. Connect to your service See how to connect.
  2. Create a server Run the following command using your connection details: 
    CREATE SERVER myserver 
FOREIGN DATA WRAPPER postgres_fdw 
OPTIONS (host '<host>', dbname 'tsdb', port '<port>');
  3. Create user mapping Run the following command using your connection details: 
    CREATE USER MAPPING FOR tsdbadmin 
SERVER myserver 
OPTIONS (user 'tsdbadmin', password '<password>');
  4. Import a foreign schema (recommended) or create a foreign table
    • Import the whole schema: 
      CREATE SCHEMA foreign_stuff;

IMPORT FOREIGN SCHEMA public 
FROM SERVER myserver 
INTO foreign_stuff ;
    • Alternatively, import a limited number of tables: 
      CREATE SCHEMA foreign_stuff;

IMPORT FOREIGN SCHEMA public 
LIMIT TO (table1, table2) 
FROM SERVER myserver 
INTO foreign_stuff;
    • Create a foreign table. Skip if you are importing a schema: 
      CREATE FOREIGN TABLE films (
    code        char(5) NOT NULL,
    title       varchar(40) NOT NULL,
    did         integer NOT NULL,
    date_prod   date,
    kind        varchar(10),
    len         interval hour to minute
)
SERVER film_server;
A user with the tsdbadmin role assigned already has the required USAGE permission to create FDWs. You can enable another user, without the tsdbadmin role assigned, to query foreign data. To do so, explicitly grant the permission. For example, for a new grafana user:
CREATE USER grafana;
       
GRANT grafana TO tsdbadmin;

CREATE SCHEMA fdw AUTHORIZATION grafana;

CREATE SERVER db1 FOREIGN DATA WRAPPER postgres_fdw 
OPTIONS (host '<host>', dbname 'tsdb', port '<port>');

CREATE USER MAPPING FOR grafana SERVER db1 
OPTIONS (user 'tsdbadmin', password '<password>');

GRANT USAGE ON FOREIGN SERVER db1 TO grafana;

SET ROLE grafana;

IMPORT FOREIGN SCHEMA public 
       FROM SERVER db1 
       INTO fdw;