Revert change to PruneEmptyPlans.java

Author: astefan

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

@@ -9,33 +9,13 @@
 
 import org.elasticsearch.xpack.esql.plan.logical.LogicalPlan;
 import org.elasticsearch.xpack.esql.plan.logical.UnaryPlan;
-import org.elasticsearch.xpack.esql.plan.logical.join.InlineJoin;
-import org.elasticsearch.xpack.esql.plan.logical.join.StubRelation;
 import org.elasticsearch.xpack.esql.plan.logical.local.EmptyLocalSupplier;
 import org.elasticsearch.xpack.esql.plan.logical.local.LocalRelation;
 
 public final class PruneEmptyPlans extends OptimizerRules.OptimizerRule<UnaryPlan> {
 
     public static LogicalPlan skipPlan(UnaryPlan plan) {
-        // this basically is a decision to create a different shortcut for an empty plan for the right hand side of an InlineJoin
-        // where the StubRelation is the EsRelation/LocalRelation equivalent
-        return hasStubRelation(plan)
-            ? new StubRelation(plan.source(), plan.output())
-            : new LocalRelation(plan.source(), plan.output(), EmptyLocalSupplier.EMPTY);
-    }
-
-    private static boolean hasStubRelation(LogicalPlan plan) {
-        for (var child : plan.children()) {
-            if (child instanceof StubRelation) {
-                return true;
-            } else if (child instanceof InlineJoin) {
-                // we don't want to find the StubRelation of a different InlineJoin
-                return false;
-            } else {
-                return hasStubRelation(child);
-            }
-        }
-        return false;
+        return new LocalRelation(plan.source(), plan.output(), EmptyLocalSupplier.EMPTY);
     }
 
     @Override

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

@@ -105,11 +105,11 @@ protected LogicalPlan rule(LogicalPlan plan) {
                         // project the correct output (the one of the former inlinejoin) and remove the InlineJoin altogether,
                         // replacing it with its right-hand side followed by its left-hand side
                         plan = new Project(newIJ.source(), newIJ.right(), newIJ.output());
-                    } else {
+                    } else { // this is a standalone Aggregate
                         plan = localRelation(aggregate.source(), newEvals);
                     }
                 } else {
-                    if (ij.get() != null) {
+                    if (ij.get() != null) { // this is an Aggregate part of right-hand side of an InlineJoin
                         // only update the Aggregate and add an Eval for the removed aggregations
                         plan = ij.get().transformUp(Aggregate.class, agg -> {
                             // if the aggregate is not the one we are looking for, return it unchanged
@@ -121,7 +121,7 @@ protected LogicalPlan rule(LogicalPlan plan) {
                             newPlan = new Project(aggregate.source(), newPlan, newProjections);
                             return newPlan;
                         });
-                    } else {
+                    } else { // this is a standalone Aggregate
                         plan = aggregate.with(aggregate.child(), aggregate.groupings(), newAggs);
                         plan = new Eval(aggregate.source(), plan, newEvals);
                         plan = new Project(aggregate.source(), plan, newProjections);