Preserve ORDER BY in Unparser for projection -> order by pattern

[adriangb]

Because of #15886 a parse -> unparse -> parse loop changed the query so that it would give incorrect results.

[adriangb]

@alamb @goldmedal @y-f-u could you folks take a look at this since you originally added this bit of code in #11527? As far as I can tell this has kept all of those tests passing and only produced some formatting changes in one test's SQL, but I'm not familiar with the Unparser code in general so this needs some critical thought.

[adriangb]

We can probably move this to a test in plan_to_sql.rs but I struggled a bit translating it since there's limited functions available (e.g. count(*)). I do also think e2e tests with data are useful in that they don't require a specific SQL representation as long as query semantics are maintained. But I will try to port again once we get some initial feedback here.

[adriangb]

Formatted difference:

- @"SELECT
-   j1.j1_id,
-   j1.j1_string,
-   lochierarchy
- FROM (
-   SELECT
-     j1.j1_id,
-     j1.j1_string,
-     (grouping(j1.j1_id) + grouping(j1.j1_string)) AS lochierarchy,
-     grouping(j1.j1_string),
-     grouping(j1.j1_id)
-   FROM j1
-   GROUP BY ROLLUP (j1.j1_id, j1.j1_string)
-   ORDER BY
-     lochierarchy DESC NULLS FIRST,
-     CASE
-       WHEN ((grouping(j1.j1_id) + grouping(j1.j1_string)) = 0) THEN j1.j1_id
-     END ASC NULLS LAST
- )
- LIMIT 100"
+ @r#"SELECT
+   j1.j1_id,
+   j1.j1_string,
+   lochierarchy
+ FROM (
+   SELECT
+     j1.j1_id,
+     j1.j1_string,
+     (grouping(j1.j1_id) + grouping(j1.j1_string)) AS lochierarchy,
+     grouping(j1.j1_string),
+     grouping(j1.j1_id)
+   FROM j1
+   GROUP BY ROLLUP (j1.j1_id, j1.j1_string)
+ )
+ ORDER BY
+   lochierarchy DESC NULLS FIRST,
+   CASE
+     WHEN (("grouping(j1.j1_id)" + "grouping(j1.j1_string)") = 0) THEN j1.j1_id
+   END ASC NULLS LAST
+ LIMIT 100"#

As you can see the ORDER BY got moved outside of the subquery, which is what we want.

[adriangb]

I've added a property based test that asserts the property that results should be the same after unparsing and re-parsing a query given the same input data*. I think this is a good test because:

• It uses real world queries and data
• It's a property based test on the thing users care about in general (correct results) instead of e.g. asserting the unparsed SQL matches some shape

*: Not all queries have a deterministic sort order. I check if the original query has a known output ordering and if it doesn't I sort both outputs.

These tests show that without these fixes there are two issues for ClickBench queries:

• Column name quoting is missing for columns with uppercase letters
• The ORDER BY bug

Here is the failure output (also relevant to judge since the tests are being added):

3 Clickbench test(s) failed:

Results mismatch for q15.
Original SQL:
-- Must set for ClickBench hits_partitioned dataset. See https://github.com/apache/datafusion/issues/16591
-- set datafusion.execution.parquet.binary_as_string = true

SELECT "UserID", COUNT(*) FROM hits GROUP BY "UserID" ORDER BY COUNT(*) DESC LIMIT 10;

Unparsed SQL:
SELECT
  hits."UserID",
  "count(*)"
FROM
  (
    SELECT
      hits."UserID",
      count(1) AS "count(*)",
      count(1)
    FROM
      hits
    GROUP BY
      hits."UserID" ORDER BY count(1) DESC NULLS FIRST
  ) LIMIT 10

---

Results mismatch for q16.
Original SQL:
-- Must set for ClickBench hits_partitioned dataset. See https://github.com/apache/datafusion/issues/16591
-- set datafusion.execution.parquet.binary_as_string = true

SELECT "UserID", "SearchPhrase", COUNT(*) FROM hits GROUP BY "UserID", "SearchPhrase" ORDER BY COUNT(*) DESC LIMIT 10;

Unparsed SQL:
SELECT
  hits."UserID",
  hits."SearchPhrase",
  "count(*)"
FROM
  (
    SELECT
      hits."UserID",
      hits."SearchPhrase",
      count(1) AS "count(*)",
      count(1)
    FROM
      hits
    GROUP BY
      hits."UserID", hits."SearchPhrase" ORDER BY count(1) DESC NULLS FIRST
  ) LIMIT 10

---

Results mismatch for q18.
Original SQL:
-- Must set for ClickBench hits_partitioned dataset. See https://github.com/apache/datafusion/issues/16591
-- set datafusion.execution.parquet.binary_as_string = true

SELECT "UserID", extract(minute FROM to_timestamp_seconds("EventTime")) AS m, "SearchPhrase", COUNT(*) FROM hits GROUP BY "UserID", m, "SearchPhrase" ORDER BY COUNT(*) DESC LIMIT 10;

Unparsed SQL:
SELECT
  hits."UserID",
  m,
  hits."SearchPhrase",
  "count(*)"
FROM
  (
    SELECT
      hits."UserID",
      date_part('MINUTE', to_timestamp_seconds(hits."EventTime")) AS m,
      hits."SearchPhrase",
      count(1) AS "count(*)",
      count(1)
    FROM
      hits
    GROUP BY
      hits."UserID", date_part('MINUTE', to_timestamp_seconds(hits."EventTime")), hits."SearchPhrase" ORDER BY count(1) DESC NULLS FIRST
  ) LIMIT 10