0.4.0

0.4.0 brings lots of new features including switch, select ![] and numbers with underscores. We have initial (unpublished) bindings to Elixir. And there's the usual improvements to fixes & documentation (only a minority are listed below in this release).

0.4.0 also has some breaking changes: table is let, dialect is renamed to target, and the compiler's API has changed. Full details below.

Features:

• Defining a temporary table is now expressed as let rather than table (@aljazerzen, #1315). See the tables docs for details.

• Experimental: The switch function sets a variable to a value based on one of several expressions (@aljazerzen, #1278).

  derive var = switch [
    score <= 10 -> "low",
    score <= 30 -> "medium",
    score <= 70 -> "high",
    true -> "very high",
  ]
  

  ...compiles to:

  SELECT
    *,
    CASE
      WHEN score <= 10 THEN 'low'
      WHEN score <= 30 THEN 'medium'
      WHEN score <= 70 THEN 'high'
      ELSE 'very high'
    END AS var
  FROM
    bar

  Check out the switch docs for more details.

• Experimental: Columns can be excluded by name with select (@aljazerzen, #1329)

  from albums
  select ![title, composer]
  

• Experimental: append transform, equivalent to UNION ALL in SQL. (@aljazerzen, #894)

  from employees
  append managers
  

  Check out the append docs for more details.

• Numbers can contain underscores, which can make reading long numbers easier (@max-sixty, #1467):

  from numbers
  select [
      small = 1.000_000_1,
      big = 5_000_000,
  ]
  

• The SQL output contains a comment with the PRQL compiler version (@aljazerzen, #1322)

• dialect is renamed to target, and its values are prefixed with sql. (@max-sixty, #1388); for example:

  prql target:sql.bigquery  # previously was `dialect:bigquery`
  
  from employees
  

  This gives us the flexibility to target other languages than SQL in the long term.

• Tables definitions can contain a bare s-string (@max-sixty, #1422), which enables us to include a full CTE of SQL, for example:

  let grouping = s"""
    SELECT SUM(a)
    FROM tbl
    GROUP BY
      GROUPING SETS
      ((b, c, d), (d), (b, d))
  """
  

• Ranges supplied to in can be half-open (@aljazerzen, #1330).

• The crate's external API has changed to allow for compiling to intermediate representation. This also affects bindings. See prql_compiler docs for more details.

Fixes:

[This release, the changelog only contains a subset of fixes]

• Allow interpolations in table s-strings (@aljazerzen, #1337)

Documentation:

[This release, the changelog only contains a subset of documentation improvements]

• Add docs on aliases in
  Select
• Add JS template literal and multiline example (@BCsabaEngine, #1432)
• JS template literal and multiline example (@BCsabaEngine, #1432)
• Improve prql-compiler docs & examples (@aljazerzen, #1515)
• Fix string highlighting in book (@max-sixty, #1264)

Web:

• The playground allows querying some sample data. As before, the result updates
  on every keystroke. (@aljazerzen, #1305)

Integrations:

[This release, the changelog only contains a subset of integration improvements]

• Added Elixir integration exposing PRQL functions as NIFs (#1500, @kasvith)
• Exposed Elixir flavor with exceptions (#1513, @kasvith)
• Rename prql-compiler binary to prqlc (@aljazerzen #1515)

Internal changes:

[This release, the changelog only contains a subset of internal changes]

• Add parsing for negative select (@max-sixty, #1317)
• Allow for additional builtin functions (@aljazerzen, #1325)
• Add an automated check for typos (@max-sixty, #1421)
• Add tasks for running playground & book (@max-sixty, #1265)
• Add tasks for running tests on every file change (@max-sixty, #1380)

New contributors:

• @EArazli, with #1359
• @boramalper, with #1362
• @allurefx, with #1377
• @bcho, with #1375
• @JettChenT, with #1385
• @BlurrechDev, with #1411
• @BCsabaEngine, with #1432
• @kasvith, with #1500