Distributed queries

Run queries across multiple servers.

Distributed query

A distributed query pulls data from several databases with one SQL statement. In PostgreSQL a Foreign Data Wrapper (FDW) lets a remote table act like a local one.

CREATE FOREIGN TABLE remote_orders (id INT)
SERVER remote_server;

A distributed query calls a remote table.

Distributed query — details

Federation is a layout where each node keeps its own data but a central query joins them all. A JOIN can run across remote and local tables.

Exercise Distributed query

Create the remote_orders foreign table from remote_server: CREATE FOREIGN TABLE remote_orders (id INT) SERVER remote_server.

Show example solution

CREATE FOREIGN TABLE remote_orders (id INT) SERVER remote_server;

Test yourself

What does a distributed query combine?
- An index
- One table
- One column
- Several databases
Show answer

Several databases — A distributed query combines several databases.

Create a foreign table

CREATE FOREIGN TABLE remote_orders (id INT) SERVER ____

Show answer

CREATE FOREIGN TABLE remote_orders (id INT) SERVER remote_server

Distributed queries: match the terms

distributed

distributed
foreign

foreign
federation

federation
remote

remote

Next lesson: MPP

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