### Elasticsearch Version

main

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

all

### Problem Description

Do this

### Steps to Reproduce

```
rm /tmp/evil
for a in {0..9}; do
   for b in {0..9}; do
      echo '{"index": {}}' >> /tmp/evil
      echo '{"a": '$a', "b": '$b'}' >> /tmp/evil
   done
done
echo >> /tmp/evil

curl -uelastic:password -XDELETE localhost:9200/test
curl -HContent-Type:application/json -uelastic:password -XPUT localhost:9200/test
curl -HContent-Type:application/json -uelastic:password -XPOST localhost:9200/test/_bulk --data-binary @/tmp/evil
curl -HContent-Type:application/json -uelastic:password -XPOST localhost:9200/test/_forcemerge?max_num_segments=1
curl -HContent-Type:application/json -uelastic:password -XPOST localhost:9200/test/_refresh

curl -HContent-Type:application/json -uelastic:password -XPOST localhost:9200/_esql?pretty -d'{
   "query": "FROM test | STATS MAX(a) BY a, b | KEEP a"
}'
```

### Logs (if relevant)

_No response_
x-pack/plugin/esql/compute/src/test/java/org/elasticsearch/compute/operator/ProjectOperatorTests.java
return expectedDescriptionOfSimple();
    }
    @Override
    protected void assertSimpleOutput(List<Page> input, List<Page> results) {
        long expected = input.stream().mapToInt(Page::getPositionCount).sum();
        int total = 0;
        for (Page page : results) {
            assertThat(page.getBlockCount(), equalTo(1));
            LongBlock remaining = page.getBlock(0);
            total += page.getPositionCount();
            for (int i = 0; i < page.getPositionCount(); i++) {
                assertThat(remaining.getLong(i), equalTo(expected));
                expected--;
            }
        }
        assertThat(total, equalTo(input.stream().mapToInt(Page::getPositionCount).sum()));
    }
    @Override
    protected ByteSizeValue smallEnoughToCircuitBreak() {
        assumeTrue("doesn't use big arrays so can't break", false);
        return null;
    }
    
    static CircuitBreakerService mockBreakerService(CircuitBreaker breaker) {
        CircuitBreakerService breakerService = mock(CircuitBreakerService.class);
        when(breakerService.getBreaker(CircuitBreaker.REQUEST)).thenReturn(breaker);
        return breakerService;
    }
}