Added some comments to EvalMapper.toEvaluator

Author: carlosdelest

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/evaluator/EvalMapper.java

@@ -56,6 +56,14 @@ public static ExpressionEvaluator.Factory toEvaluator(FoldContext foldCtx, Expre
     }
 
     @SuppressWarnings({ "rawtypes", "unchecked" })
+    /**
+     * Provides an ExpressionEvaluator factory to evaluate an expression.
+     *
+     * @param foldCtx the fold context for folding expressions
+     * @param exp the expression to generate an evaluator for
+     * @param layout the mapping from attributes to channels
+     * @param shardContexts the shard contexts, needed to generate queries for expressions that couldn't be pushed down to Lucene
+     */
     public static ExpressionEvaluator.Factory toEvaluator(
         FoldContext foldCtx,
         Expression exp,