```
ROW a="b c d"
| DISSECT a "%{b} %{} %{d}"
```
returns

```
       a       |       b       |               |       d       
---------------+---------------+---------------+---------------
b c d          |b              |null           |d 
```

it should ignore the empty pattern instead, and only return `a, b, d`
x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/parser/StatementParserTests.java
new Alias(EMPTY, "b", integer(2)),
                    new Alias(EMPTY, "@timestamp", new Literal(EMPTY, "2022-26-08T00:00:00", KEYWORD))
                )
            ),
            statement("row a.b.c = 1, `b` = 2, `@timestamp`=\"2022-26-08T00:00:00\"")
        );
    }
    public void testCompositeCommand() {
        assertEquals(
            new Filter(EMPTY, new Row(EMPTY, List.of(new Alias(EMPTY, "a", integer(1)))), TRUE),
            statement("row a = 1 | where true")
        );
    }
    public void testMultipleCompositeCommands() {
        assertEquals(
            new Filter(
                EMPTY,
                new Filter(EMPTY, new Filter(EMPTY, new Row(EMPTY, List.of(new Alias(EMPTY, "a", integer(1)))), TRUE), FALSE),
                TRUE
            ),
            statement("row a = 1 | where true | where false | where true")
        );
    }
    public void testEval() {
        assertEquals(
            new Eval(EMPTY, PROCESSING_CMD_INPUT, List.of(new Alias(EMPTY, "b", attribute("a")))),
            processingCommand("eval b = a")
        );
        assertEquals(
            new Eval(