DROP of EVAL planning issues

[dnhatn]

PUT /test/_doc/1?refresh
{
    "k": "a",
    "v": 1
}

PUT /test/_doc/2?refresh
{
    "k": "a",
    "v": 2
}

POST /_query?error_trace
{
    "query": "FROM test | EVAL k1 = k | STATS avg(v) BY k, k1 | DROP k1"
}

"reason": "Found 1 problem\nline 1:27: Plan [Aggregate[[k{f}#199, k1{r}#192],[SUM(v{f}#198) AS $$SUM$avg(v)$0, COUNT(v{f}#198) AS $$COUNT$avg(v)$1, k{f}#199]]] optimized incorrectly due to missing references [k1{r}#192]",

And without aggs

POST /_query?error_trace
{
    "query": "FROM test | EVAL k1 = k | STATS BY k, k1 | DROP k1"
}

"stack_trace": "java.lang.NullPointerException: Cannot invoke \"org.elasticsearch.xpack.esql.planner.Layout$ChannelSet.nameIds()\" because the return value of 
 \"java.util.List.get(int)\" is null
\tat org.elasticsearch.xpack.esql.planner.ExchangeLayout.get(ExchangeLayout.java:36)
\tat org.elasticsearch.xpack.esql.planner.AbstractPhysicalOperationProviders.groupingPhysicalOperation(AbstractPhysicalOperationProviders.java:122)
\tat org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.planAggregation(LocalExecutionPlanner.java:234)
\tat org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.plan(LocalExecutionPlanner.java:182)
\tat org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.planProject(LocalExecutionPlanner.java:508)
\tat org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.plan(LocalExecutionPlanner.java:196)
\tat org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.planLimit(LocalExecutionPlanner.java:548)
\tat org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.plan(LocalExecutionPlanner.java:200)
\tat org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.planOutput(LocalExecutionPlanner.java:267)
\tat org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.plan(LocalExecutionPlanner.java:224)
\tat org.elasticsearch.xpack.esql.planner.LocalExecutionPlanner.plan(LocalExecutionPlanner.java:167)
\tat org.elasticsearch.xpack.esql.plugin.ComputeService.runCompute(ComputeService.java:441)
\tat org.elasticsearch.xpack.esql.plugin.ComputeService.execute(
        ComputeService.java:208)
\tat org.elasticsearch.xpack.esql.plugin.TransportEsqlQueryAction.lambda$innerExecute$4(TransportEsqlQueryAction.java:166)

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[alex-spies]

Re-opening as I found another reproducer:

FROM employees
| EVAL k = languages, k1 = k
| STATS c = 3*COUNT() BY languages, k, k1, languages
| DROP k

Found 1 problem
line 3:3: Plan [Aggregate[[languages{f}#101, k{r}#95],[COUNT([2a][KEYWORD]) AS $$COUNT$3*count(*)$0, languages{f}#101]]] optimized incorrectly due to missing references [k{r}#95]