abstract function

Author: not-napoleon

x-pack/plugin/esql-core/src/main/java/org/elasticsearch/xpack/esql/core/expression/Attribute.java

@@ -134,4 +134,9 @@ public String nodeString() {
     }
 
     protected abstract String label();
+
+    /**
+     * @return true if the attribute represents a TSDB dimension type
+     */
+    public abstract boolean isDimension();
 }

x-pack/plugin/esql-core/src/main/java/org/elasticsearch/xpack/esql/core/expression/EmptyAttribute.java

@@ -44,6 +44,11 @@ protected String label() {
         return "e";
     }
 
+    @Override
+    public boolean isDimension() {
+        return false;
+    }
+
     @Override
     public boolean resolved() {
         return true;