response to PR feedback

Author: not-napoleon

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/IgnoreNullMetrics.java

@@ -17,6 +17,7 @@
 import org.elasticsearch.xpack.esql.plan.logical.EsRelation;
 import org.elasticsearch.xpack.esql.plan.logical.Filter;
 import org.elasticsearch.xpack.esql.plan.logical.LogicalPlan;
+import org.elasticsearch.xpack.esql.plan.logical.TimeSeriesAggregate;
 import org.elasticsearch.xpack.esql.plan.logical.UnresolvedRelation;
 import org.elasticsearch.xpack.esql.rule.Rule;
 
@@ -58,7 +59,7 @@ public LogicalPlan apply(LogicalPlan logicalPlan) {
     private Set<Attribute> collectMetrics(LogicalPlan logicalPlan) {
         Set<Attribute> metrics = new HashSet<>();
         logicalPlan.forEachDown(p -> {
-            if (p instanceof Aggregate) {
+            if (p instanceof TimeSeriesAggregate) {
                 p.forEachExpression(Attribute.class, attr -> {
                     if (attr.isMetric()) {
                         metrics.add(attr);

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/IgnoreNullMetricsTests.java

@@ -182,4 +182,25 @@ public void testSkipCoalescedMetrics() {
         FieldAttribute attribute = as(condition.field(), FieldAttribute.class);
         assertEquals("metric_1", attribute.fieldName().string());
     }
+
+    /**
+     * check that stats blocks after the first are not sourced for adding metrics to the filter
+     */
+    public void testMultipleStats() {
+        LogicalPlan actual = analyze("""
+            TS test
+            | STATS m = max(max_over_time(metric_1))
+            | STATS sum(m)
+            | LIMIT 10
+            """);
+        Limit limit = as(actual, Limit.class);
+        Aggregate sumAgg = as(limit.child(), Aggregate.class);
+        Aggregate outerAgg = as(sumAgg.child(), Aggregate.class);
+        Aggregate tsAgg = as(outerAgg.child(), Aggregate.class);
+        Filter filter = as(tsAgg.child(), Filter.class);
+        IsNotNull condition = as(filter.condition(), IsNotNull.class);
+        FieldAttribute attribute = as(condition.field(), FieldAttribute.class);
+        assertEquals("metric_1", attribute.fieldName().string());
+
+    }
 }