```
show functions | rename synopsis AS foo | stats bar = count(*) by foo | drop foo
```

```
{
    "error": {
        "root_cause": [
            {
                "type": "null_pointer_exception",
                "reason": "Cannot invoke \"org.elasticsearch.xpack.ql.expression.Attribute.id()\" because \"sourceAttribute\" is null"
            }
        ],
        "type": "null_pointer_exception",
        "reason": "Cannot invoke \"org.elasticsearch.xpack.ql.expression.Attribute.id()\" because \"sourceAttribute\" is null"
    },
    "status": 500
}
```

```
[2023-11-14T09:49:51,479][WARN ][r.suppressed             ] [runTask-0] path: /_query, params: {format=txt}, status: 500 java.lang.NullPointerException: Cannot invoke "org.elasticsearch.xpack.ql.expression.Attribute.id()" because "sourceAttribute" is null
        at org.elasticsearch.xpack.esql.planner.EsPhysicalOperationProviders.ordinalGroupingOperatorFactory(EsPhysicalOperationProviders.java:172)
        at org.elasticsearch.xpack.esql.planner.AbstractPhysicalOperationProviders.groupingPhysicalOperation(AbstractPhysicalOperationProviders.java:148)
        at org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.planAggregation(LocalExecutionPlanner.java:234)
        at org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.plan(LocalExecutionPlanner.java:182)
        at org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.planAggregation(LocalExecutionPlanner.java:233)
        at org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.plan(LocalExecutionPlanner.java:182)
        at org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.planProject(LocalExecutionPlanner.java:571)
        at org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.plan(LocalExecutionPlanner.java:196)
        at org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.planLimit(LocalExecutionPlanner.java:610)
        at org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.plan(LocalExecutionPlanner.java:200)
        at org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.planOutput(LocalExecutionPlanner.java:310)
        at org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.plan(LocalExecutionPlanner.java:224)
        at org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.plan(LocalExecutionPlanner.java:168)
        at org.elasticsearch.xpack.esql.plugin.ComputeService.runCompute(ComputeService.java:260)
```
x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/LogicalPlanOptimizerTests.java
assertThat(f, hasSize(1));
        assertThat(f.get(0).name(), is("a"));
        var limit = as(eval.child(), Limit.class);
        var agg = as(limit.child(), Aggregate.class);
        var aggs = agg.aggregates();
        var a = as(aggs.get(0), Alias.class);
        assertThat(a.name(), startsWith("__a_SUM@"));
        var sum = as(a.child(), Sum.class);
        a = as(aggs.get(1), Alias.class);
        assertThat(a.name(), startsWith("__a_COUNT@"));
        var count = as(a.child(), Count.class);
        assertThat(Expressions.names(agg.groupings()), contains("last_name"));
    }
    /**
     * Expects
     * EsqlProject[[a{r}#3, c{r}#6, s{r}#9, last_name{f}#15]]
     * \_Eval[[s{r}#9 / c{r}#6 AS a]]
     *   \_Limit[10000[INTEGER]]
     *     \_Aggregate[[last_name{f}#15],[COUNT(salary{f}#16) AS c, SUM(salary{f}#16) AS s, last_name{f}#15]]
     *       \_EsRelation[test][_meta_field{f}#17, emp_no{f}#11, first_name{f}#12, ..]
     */
    public void testClashingAggAvgReplacement() {
        var plan = plan("""
            from test
            | stats a = avg(salary), c = count(salary), s = sum(salary) by last_name
            """);
        assertThat(Expressions.names(plan.output()), contains("a", "c", "s", "last_name"));
        var project = as(plan, EsqlProject.class);
        var eval = as(project.child(), Eval.class);
        var f = eval.fields();