diff --git a/sql/server/src/main/java/org/elasticsearch/xpack/sql/expression/function/scalar/processor/definition/ProcessorDefinition.java b/sql/server/src/main/java/org/elasticsearch/xpack/sql/expression/function/scalar/processor/definition/ProcessorDefinition.java
index e8b7a7fd7f0..8e5692192c3 100644
--- a/sql/server/src/main/java/org/elasticsearch/xpack/sql/expression/function/scalar/processor/definition/ProcessorDefinition.java
+++ b/sql/server/src/main/java/org/elasticsearch/xpack/sql/expression/function/scalar/processor/definition/ProcessorDefinition.java
@@ -37,6 +37,13 @@ public abstract class ProcessorDefinition extends Node<ProcessorDefinition> impl
         // No fields needed
     }
 
+    /**
+     * Resolve {@link Attribute}s which are unprocessable into
+     * {@link ColumnReference}s which are processable.
+     *
+     * @return {@code this} if the resolution doesn't change the
+     *      definition, a new {@link ProcessorDefinition} otherwise
+     */
     public abstract ProcessorDefinition resolveAttributes(AttributeResolver resolver);
     public interface AttributeResolver {
         ColumnReference resolve(Attribute attribute);