Fix few bug with the current implemntation

Author: afoucret

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

@@ -18,6 +18,7 @@
 import org.elasticsearch.xpack.esql.plan.logical.Project;
 import org.elasticsearch.xpack.esql.plan.logical.RegexExtract;
 import org.elasticsearch.xpack.esql.plan.logical.UnaryPlan;
+import org.elasticsearch.xpack.esql.plan.logical.inference.Rerank;
 import org.elasticsearch.xpack.esql.plan.logical.join.Join;
 import org.elasticsearch.xpack.esql.plan.logical.join.JoinTypes;
 
@@ -52,11 +53,14 @@ public LogicalPlan rule(Limit limit, LogicalOptimizerContext ctx) {
                     mvx = new MvExpand(mvx.source(), mvx.child(), mvx.target(), mvx.expanded(), limitVal);
                 }
                 return mvx.replaceChild(limit.replaceChild(mvx.child()));
-            }
-            // check if there's a 'visible' descendant limit lower than the current one
-            // and if so, align the current limit since it adds no value
-            // this applies for cases such as | limit 1 | sort field | limit 10
-            else {
+            } else if (unary instanceof Rerank) {
+                Limit descendantLimit = descendantLimit(unary);
+                if (descendantLimit == null) {
+                    var rerankerDefaultLimit = ctx.configuration().resultTruncationDefaultSize();
+                    var rerankerLimit = new Limit(limit.source(), Literal.of(limit.limit(), rerankerDefaultLimit), unary.child());
+                    return limit.replaceChild(unary.replaceChild(rerankerLimit));
+                }
+            } else {
                 Limit descendantLimit = descendantLimit(unary);
                 if (descendantLimit != null) {
                     var l1 = (int) limit.limit().fold(ctx.foldCtx());

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/plan/logical/inference/Rerank.java

@@ -68,11 +68,6 @@ public String getWriteableName() {
         return ENTRY.name;
     }
 
-    @Override
-    public String commandName() {
-        return "RERANK";
-    }
-
     @Override
     public UnaryPlan replaceChild(LogicalPlan newChild) {
         return new Rerank(source(), newChild, inferenceId(), queryText, input);