fix minor

Author: JingsongLi

paimon-core/src/main/java/org/apache/paimon/table/source/FullTextSearchBuilderImpl.java

@@ -22,6 +22,9 @@
 import org.apache.paimon.table.InnerTable;
 import org.apache.paimon.types.DataField;
 
+import static org.apache.paimon.utils.Preconditions.checkArgument;
+import static org.apache.paimon.utils.Preconditions.checkNotNull;
+
 /** Implementation for {@link FullTextSearchBuilder}. */
 public class FullTextSearchBuilderImpl implements FullTextSearchBuilder {
 
@@ -57,11 +60,15 @@ public FullTextSearchBuilder withQueryText(String queryText) {
 
     @Override
     public FullTextScan newFullTextScan() {
+        checkNotNull(textColumn, "Text column must be set via withTextColumn()");
         return new FullTextScanImpl(table, textColumn);
     }
 
     @Override
     public FullTextRead newFullTextRead() {
+        checkArgument(limit > 0, "Limit must be positive, set via withLimit()");
+        checkNotNull(textColumn, "Text column must be set via withTextColumn()");
+        checkNotNull(queryText, "Query text must be set via withQueryText()");
         return new FullTextReadImpl(table, limit, textColumn, queryText);
     }
 }

paimon-spark/paimon-spark-common/src/main/scala/org/apache/paimon/spark/PaimonBaseScan.scala

@@ -55,6 +55,10 @@ abstract class PaimonBaseScan(table: InnerTable)
   }
 
   private def evalGlobalIndexSearch(): GlobalIndexResult = {
+    if (pushedVectorSearch.isDefined && pushedFullTextSearch.isDefined) {
+      throw new UnsupportedOperationException(
+        "Cannot push down both vector search and full-text search simultaneously.")
+    }
     if (pushedVectorSearch.isDefined) {
       return evalVectorSearch()
     }