Update javadoc

Signed-off-by: Chen Dai <daichen@amazon.com>

Author: dai-chen

core/src/main/java/org/opensearch/sql/calcite/CalciteRelNodeVisitor.java

@@ -193,15 +193,12 @@ public RelNode analyze(UnresolvedPlan unresolved, CalcitePlanContext context) {
     return unresolved.accept(this, context);
   }
 
-  /**
-   * Override visitChildren to auto-materialize MAP dotted paths after children are visited. When a
-   * command references dotted paths into MAP columns, they are materialized as flat columns before
-   * the command's own logic runs.
-   */
   @Override
   public RelNode visitChildren(Node node, CalcitePlanContext context) {
     RelNode result = super.visitChildren(node, context);
     if (node instanceof UnresolvedPlan plan) {
+      // Materialize MAP dotted paths as flat columns after children are analyzed
+      // (so MAP/struct types are known) but before the command's own visit logic runs.
       mapPathMaterializer.materializePaths(plan, context);
     }
     return result;

core/src/main/java/org/opensearch/sql/calcite/MapPathPreMaterializer.java

@@ -73,15 +73,17 @@ private void doMaterializeMapPaths(List<Field> fields, CalcitePlanContext contex
     Set<String> existingFields =
         new HashSet<>(context.relBuilder.peek().getRowType().getFieldNames());
     List<RexNode> newColumns = new ArrayList<>();
-    for (Field f : fields) {
+    for (Field field : fields) {
       try {
-        RexNode resolved = rexVisitor.analyze(f, context);
-        String name = f.getField().toString();
+        RexNode resolved = rexVisitor.analyze(field, context);
+        String name = field.getField().toString();
         if (resolved.getKind() == SqlKind.ITEM && !existingFields.contains(name)) {
           newColumns.add(context.relBuilder.alias(resolved, name));
+          existingFields.add(name);
         }
       } catch (RuntimeException e) {
-        log.debug("Skipping field resolution for '{}': {}", f.getField(), e.getMessage(), e);
+        // Skip unresolvable fields (e.g. wildcards); let the command itself handle them
+        log.debug("Skipping field resolution for '{}': {}", field.getField(), e.getMessage(), e);
       }
     }
 

core/src/test/java/org/opensearch/sql/calcite/MapPathPreMaterializerTest.java

@@ -56,7 +56,6 @@
 import org.opensearch.sql.calcite.utils.OpenSearchTypeFactory;
 import org.opensearch.sql.executor.QueryType;
 
-/** Unit tests for {@link MapPathPreMaterializer}. */
 @ExtendWith(MockitoExtension.class)
 public class MapPathPreMaterializerTest {