postgresql: better handle DISTINCT clause

[holymonson]

At present sql-formatter produces:

SELECT
  DISTINCT ON (c1, c2) c1,
  c2
FROM
  t1;

But we expect:

SELECT
DISTINCT ON (c1, c2)
  c1,
  c2
FROM
  t1;

-- or 

SELECT DISTINCT ON (c1, c2)
  c1,
  c2
FROM
  t1;

[nene]

The latest version in master produces:

SELECT
  DISTINCT
  ON (c1, c2) c1,
  c2
FROM
  t1;

This isn't really better either :(

[nene]

With 9.0.0 there's another slight change. It now gets formatted as:

SELECT DISTINCT
  ON (c1, c2) c1,
  c2
FROM
  t1;

Still not there though :(

[QoVoQ]

const reservedSelect = expandPhrases(['SELECT [ALL | DISTINCT] [ON]']);
should be able to solve the issue?

[nene]

This would result in:

SELECT DISTINCT ON
  (c1, c2) c1,
  c2
FROM
  t1;

which isn't better. What one really wants is:

SELECT DISTINCT ON (c1, c2)
  c1,
  c2
FROM
  t1;