fix(sql): constant in explicit group by should not remove parallel optimisation

[nwoolmer]

Closes #4380

This is related to Clickbench Q34. Adding an explicit group by that includes an effectively constant expression would prevent generation of Async Group By node.

Change also sorted the ordering of the SqlOptimiser tests. This makes locating the relevant test hard. It is here:

questdb/core/src/test/java/io/questdb/test/griffin/SqlOptimiserTest.java

Lines 194 to 235 in b74fb84

	public void testConstantInGroupByDoesNotPreventOptimisation() throws Exception {
	assertMemoryLeak(() -> {
	ddl("create table hits (\n" +
	" URL string, ts timestamp\n" +
	") timestamp(ts) partition by day wal");
	insert("insert into hits (URL, ts) values ('abc', 0), ('abc', 1), ('def', 2), ('ghi', 3)");
	drainWalQueue();
	String q1 = "SELECT 1, URL, COUNT(*) AS c FROM hits ORDER BY c DESC LIMIT 10;";
	String q2 = "SELECT 1, URL, COUNT(*) AS c FROM hits GROUP BY 1, URL ORDER BY c DESC LIMIT 10;";
	String q3 = "SELECT 1, URL, COUNT(*) AS c FROM hits GROUP BY URL, 1 ORDER BY c DESC LIMIT 10;";
	String q4 = "SELECT 1, URL, COUNT(*) AS c FROM hits GROUP BY 1, 2 ORDER BY c DESC LIMIT 10;";
	String expectedSql = "1\tURL\tc\n" +
	"1\tabc\t2\n" +
	"1\tghi\t1\n" +
	"1\tdef\t1\n";
	String expectedPlan = "Sort light lo: 10\n" +
	" keys: [c desc]\n" +
	" VirtualRecord\n" +
	" functions: [1,URL,c]\n" +
	" Async Group By workers: 1\n" +
	" keys: [URL]\n" +
	" values: [count(*)]\n" +
	" filter: null\n" +
	" DataFrame\n" +
	" Row forward scan\n" +
	" Frame forward scan on: hits\n";
	assertSql(expectedSql, q1);
	assertSql(expectedSql, q2);
	assertSql(expectedSql, q3);
	assertSql(expectedSql, q4);
	assertPlan(q1, expectedPlan);
	assertPlan(q2, expectedPlan);
	assertPlan(q3, expectedPlan);
	assertPlan(q4, expectedPlan);
	});
	}

Control query:

SELECT 1, URL, COUNT(*) AS c FROM hits ORDER BY c DESC LIMIT 10;

Gives:

Sort light lo: 10
  keys: [c desc]
    VirtualRecord
      functions: [1,URL,c]
        Async Group By workers: 16
          keys: [URL]
          values: [count(*)]
          filter: null
            DataFrame
                Row forward scan
                Frame forward scan on: hits

Problematic query:

SELECT 1, URL, COUNT(*) AS c FROM hits GROUP BY 1, URL ORDER BY c DESC LIMIT 10;

Plan before:

Sort light lo: 10
  keys: [c desc]
    VirtualRecord
      functions: [1,URL,c]
        GroupBy vectorized: false
          keys: [URL,1]
          values: [count(*)]
            VirtualRecord
              functions: [URL,1]
                DataFrame
                    Row forward scan
                    Frame forward scan on: hits

Plan after:

Sort light lo: 10
  keys: [c desc]
    VirtualRecord
      functions: [1,URL,c]
        Async Group By workers: 16
          keys: [URL]
          values: [count(*)]
          filter: null
            DataFrame
                Row forward scan
                Frame forward scan on: hits

[bluestreak01]

hey @nwoolmer could yuou do me a favoir and submit the tests avoiding code reformatting. I cannot read the diff unfortuantely.

[ideoma]

[PR Coverage check]

😍 pass : 1 / 1 (100.00%)

file detail

	path	covered line	new line	coverage
🔵	io/questdb/griffin/SqlOptimiser.java	1	1	100.00%