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RegreSQL, Regression Testing your SQL queries

The regresql tool implement a regression testing facility for SQL queries, and supports the PostgreSQL database system. A regression test allows to ensure known results when the code is edited. To enable that we need:

  • some code to test, here SQL queries, each in its own file,
  • a known result set for each SQL query,
  • a regression driver that runs queries again and check their result against the known expected result set.

The RegreSQL tool is that regression driver. It helps with creating the expected result set for each query and then running query files again to check that the results are still the same.

Of course, for the results the be comparable the queries need to be run against a known PostgreSQL database content.


The regresql tool is written in Go, so:

go get

This command will compile and install the command in your $GOPATH/bin, which defaults to ~/go/bin. See if you're new to the Go language.

Basic usage

Basic usage or regresql:

  • regresql init [ -C dir ]

    Creates the regresql main directories and runs all SQL queries found in your target code base (defaults to current directory).

    The -C option changes current directory to dir before running the command.

  • regresql plan [ -C dir ]

    Create query plan files for all queries. Run that command when you add new queries to your repository.

  • regresql update [ -C dir ]

    Updates the expected files from the queries, considering that the output is valid.

  • regresql test [ -C dir ]

    Runs all the SQL queries found in current directory.

    The -C option changes the current directory before running the tests.

  • regresql list [ -C dir ]

    List all SQL files found in current directory.

    The -C option changes the current directory before listing the files.

SQL query files

RegreSQL finds every .sql file in your code repository and runs them against PostgreSQL. It means you're supposed to maintain your queries as separate query files, see the excellent Clojure library to see how that's done. The project links to many implementation in other languages, including Python, PHP or Go.

SQL files might contain variables, and RegreSQL implements the same support for them as psql, see the PostgreSQL documentation about psql variables and their usage syntax and quoting rules: :foo, :'foo' and :"foo".

Test Suites

By default a Test Suite is a source directory.

File organisation

RegreSQL needs the following files and directories to run:

  • ./regresql where to register needed files

  • ./regresql/regresql.yaml

    Configuration file for the directory in which it's installed. It contains the PostgreSQL connection string where to connect to for running the regression tests and the top level directory where to find the SQL files to test against.

  • ./regresql/expected/path/to/query.yaml

    For each file query.sql found in your source tree, RegreSQL creates a subpath in ./regresql/plans with a query.yaml file. This YAML file contains query plans: that's a list of SQL parameters values to use when testing.

  • ./regresql/expected/path/to/query.out

    For each file query.sql found in your source tree, RegreSQL creates a subpath in ./regresql/expected directory and stores in query.out the expected result set of the query,

  • ./regresql/out/path/to/query.sql

    The result of running the query in query.sql is stored in query.out in the regresql/out directory subpath for it, so that it is possible to compare this result to the expected one in regresql/expected.


In a small local application the command regresql list returns the following SQL source files:

$ regresql list

After having done the following commands:

$ regresql init postgres:///chinook?sslmode=disable

$ regresql update

Now we have to edit the YAML plan files to add bindings, here's an example for a query using a single parameter, :name:

$ cat src/sql/album-by-artist.sql
-- name: list-albums-by-artist
-- List the album titles and duration of a given artist
  select album.title as album,
         sum(milliseconds) * interval '1 ms' as duration
    from album
         join artist using(artistid)
         left join track using(albumid)
   where = :name
group by album
order by album;

$ cat regresql/plans/src/sql/album-by-artist.yaml 
  name: "Red Hot Chili Peppers"

And we can now run the tests:

$ regresql test
Connecting to 'postgres:///chinook?sslmode=disable'… ✓
TAP version 13
ok 1 - src/sql/album-by-artist.1.out
ok 2 - src/sql/album-tracks.1.out
ok 3 - src/sql/artist.1.out
ok 4 - src/sql/
ok 5 - src/sql/
ok 6 - src/sql/genre-tracks.out

We can see the following files have been created by the RegreSQL tool:

$ tree regresql/
├── expected
│   └── src
│       └── sql
│           ├── album-by-artist.1.out
│           ├── album-tracks.1.out
│           ├── artist.1.out
│           ├── genre-topn.1.out
│           ├──
│           ├──
│           └── genre-tracks.out
├── out
│   └── src
│       └── sql
│           ├── album-by-artist.1.out
│           ├── album-tracks.1.out
│           ├── artist.1.out
│           ├── genre-topn.1.out
│           ├──\ 1.out
│           ├──\ 3.out
│           ├──
│           ├──
│           └── genre-tracks.out
├── plans
│   └── src
│       └── sql
│           ├── album-by-artist.yaml
│           ├── album-tracks.yaml
│           ├── artist.yaml
│           └── genre-topn.yaml
└── regress.yaml

9 directories, 21 files


This tool is inspired by the PostgreSQL regression testing framework. It's been written in the process of the Mastering PostgreSQL book as an example of an SQL framework for unit testing and regression testing.


The RegreSQL utility is released under The PostgreSQL License.


Regression Testing your SQL queries







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