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A dump and a verified restore

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Step 1 of 7 · on a machine · 5 min

A dump on a live database

What you will learn

  • Read what a PostgreSQL dump holds: tables, rows, counters and keys.
  • Take a dump of a database and restore it into a new database without touching the working one.
  • Compare a restored copy with the original by its rows and its counter.

Yesterday evening someone took a dump of the shop database: the file ~/backup/shop.dump. Today a colleague decided to check that the dump works and restored it straight into shop: the tables are there, so nothing can break.

Repeat the check, then do what the shop does every minute: add an order. You have your own student role in PostgreSQL, with no password needed. “Start” launches the server and prepares the database and the dump.

Exercise · look

Restore the dump over the live database

In ~/backup, restore yesterday's dump straight into the shop database, count the orders and add a new one.

First, predict

What will pg_restore do to the shop database?

Now start the exercise, run the command and compare your prediction with the output.

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Check yourself 1 question

How many orders were left in orders after pg_restore?

  • No duplicates got in: the primary key stopped COPY with duplicate key … Key (id)=(1) already exists.

  • CREATE TABLE failed with already exists: the table is the same one, and count(*) showed 6.

  • count(*) showed 6: pg_restore did not replace any rows, and its COPY failed on the very first id.

All 6 of today's orders stayed in orders because the dump's COPY did not get through.

Found an inaccuracy? Report an error in the lesson

Ubuntu 24.04
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