[client][hotfix] Invoke RowType#getFieldNames only once in ConverterCommons (#1920)

Author: snuyanzin

fluss-client/src/main/java/org/apache/fluss/client/converter/ConverterCommons.java

@@ -26,6 +26,7 @@
 import java.util.Arrays;
 import java.util.EnumMap;
 import java.util.HashSet;
+import java.util.List;
 import java.util.Map;
 import java.util.Set;
 
@@ -67,15 +68,15 @@ private static Map<DataTypeRoot, Set<Class<?>>> createSupportedTypes() {
 
     static void validatePojoMatchesTable(PojoType<?> pojoType, RowType tableSchema) {
         Set<String> pojoNames = pojoType.getProperties().keySet();
-        Set<String> tableNames = new HashSet<>(tableSchema.getFieldNames());
-        if (!pojoNames.equals(tableNames)) {
+        List<String> fieldNames = tableSchema.getFieldNames();
+        if (!pojoNames.containsAll(fieldNames)) {
             throw new IllegalArgumentException(
                     String.format(
                             "POJO fields %s must exactly match table schema fields %s.",
-                            pojoNames, tableNames));
+                            pojoNames, fieldNames));
         }
         for (int i = 0; i < tableSchema.getFieldCount(); i++) {
-            String name = tableSchema.getFieldNames().get(i);
+            String name = fieldNames.get(i);
             DataType dt = tableSchema.getTypeAt(i);
             PojoType.Property prop = pojoType.getProperty(name);
             validateCompatibility(dt, prop);