```
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
expectError("from text | stats", "At least one aggregation or grouping expression required in [stats]");
    }
    public void testAggsWithGroupKeyAsAgg() throws Exception {
        var queries = new String[] { """
            row a = 1, b = 2
            | stats a by a
            """, """
            row a = 1, b = 2
            | stats a by a
            | sort a
            """, """
            row a = 1, b = 2
            | stats a = a by a
            """, """
            row a = 1, b = 2
            | stats x = a by a
            """ };
        for (String query : queries) {
            expectError(query, "Cannot specify grouping expression [a] as an aggregate");
        }
    }
    public void testInlineStatsWithGroups() {
        assertEquals(
            new InlineStats(
                EMPTY,
                PROCESSING_CMD_INPUT,
                List.of(attribute("c"), attribute("d.e")),
                List.of(
                    new Alias(EMPTY, "b", new UnresolvedFunction(EMPTY, "min", DEFAULT, List.of(attribute("a")))),
                    attribute("c"),