Production Usage

SQLFluff is designed to be used both as a utility for developers but also to be part of CI/CD pipelines.

Using SQLFluff on a whole sql codebase

The exit code provided by SQLFluff when run as a command line utility is designed to assist usefulness in deployment pipelines. If no violations are found then the exit code will be 0. If violations are found then a non-zero code will be returned which can be interrogated to find out more.

  • At the moment all error states related to linting return 65.

  • An error as a result of a SQLFluff internal error will return 1.

Using SQLFluff on changes using diff-quality

For projects with large amounts of (potentially imperfect) SQL code, the full SQLFluff output could be very large, which can be distracting – perhaps the CI build for a one-line SQL change shouldn’t encourage the developer to fix lots of unrelated quality issues.

To support this use case, SQLFluff integrates with a quality checking tool called diff-quality. By running SQLFluff using diff-quality (rather than running it directly), you can limit the the output to the new or modified SQL in the branch (aka pull request or PR) containing the proposed changes.

Currently, diff-quality requires that you are using git for version control.

NOTE: Installing SQLFluff automatically installs the diff_cover package that provides the diff-quality tool.

Adding diff-quality to your builds

In your CI build script:

1. Set the current working directory to the git repository containing the SQL code to be checked.

  1. Run diff-quality, specifying SQLFluff as the underlying tool:

diff-quality --violations sqlfluff

The output will look something like:

-------------
Diff Quality
Quality Report: sqlfluff
Diff: origin/master...HEAD, staged and unstaged changes
-------------
sql/audience_size_queries/constraints/_postcondition_check_gdpr_compliance.sql (0.0%):
sql/audience_size_queries/constraints/_postcondition_check_gdpr_compliance.sql:5: Inconsistent capitalisation of unquoted identifiers.
-------------
Total:   1 line
Violations: 1 line
% Quality: 0%
-------------

These messages are basically the same as those provided directly by SQLFluff, although the format is a little different. Note that diff-quality only lists the line _numbers_, not the character position. If you need the character position, you will need to run SQLFluff directly.

For more information on diff-quality, see the [documentation](https://diff-cover.readthedocs.io/en/latest/). It covers topics such as:

  • Generating HTML reports

  • Controlling which branch to compare against (i.e. to determine new/changed lines). The default is origin/master.

  • Configuring diff-quality to return an error code if the quality is too low

  • Troubleshooting

Using pre-commit

pre-commit is a framework to manage git “hooks” triggered right before a commit is made.

A git hook is a git feature to “fire off custom scripts” when specific actions occur.

Using pre-commit with SQLFluff is a good way to provide automated linting to SQL developers.

With pre-commit, you also get the benefit of only linting/fixing the files that changed.

SQLFluff comes with two pre-commit hooks:

  • sqlfluff-lint: returns linting errors.

  • sqlfluff-fix: attempts to fix rule violations.

You should create a file named .pre-commit-config.yaml at the root of your git project, which should look like this:

repos:
- repo: https://github.com/sqlfluff/sqlfluff
  rev: 0.3.6
  hooks:
    - id: sqlfluff-lint
      # For dbt projects, this installs the dbt "extras":
      # additional_dependencies: ['.[dbt]']
    - id: sqlfluff-fix
      # Arbitrary arguments to show an example
      # args: [--rules, "L003,L014"]
      # additional_dependencies: ['.[dbt]']

When trying to use the dbt templater, uncomment the additional_dependencies to install the extras. This is equivalent to running pip install sqlfluff[dbt].

Note that you can pass the same arguments available through the CLI using args:.