Enhance error handling for entity generation by checking for primary keys and unsupported types

persist-core/src/main/java/io/ballerina/persist/introspect/Introspector.java

@@ -373,7 +373,16 @@ private void mapEntities() throws BalException {
                 }
             });
             entityBuilder.setKeys(keys);
-            entityBuilderMap.put(entityBuilder.getEntityName(), entityBuilder);
+
+            // Mark entities without primary keys as containing unsupported types
+            // This prevents IndexOutOfBoundsException during code generation
+            if (keys.isEmpty()) {
+                entityBuilder.setContainsUnsupportedTypes(true);
+                errStream.println("WARNING: Table '" + table.getTableName() +
+                        "' does not have a primary key and will be excluded from entity generation.");
+            } else {
+                entityBuilderMap.put(entityBuilder.getEntityName(), entityBuilder);
+            }
         });
         HashMap<String, Integer> ownerFieldNames = new HashMap<>();
         HashMap<String, Integer> assocFieldNames = new HashMap<>();

persist-core/src/main/java/io/ballerina/persist/nodegenerator/syntax/sources/DbModelGenSyntaxTree.java

@@ -20,17 +20,28 @@
 
 import io.ballerina.compiler.syntax.tree.SyntaxTree;
 import io.ballerina.persist.BalException;
+import io.ballerina.persist.models.Entity;
 import io.ballerina.persist.models.Module;
 import io.ballerina.persist.nodegenerator.syntax.utils.BalSyntaxUtils;
 
 public class DbModelGenSyntaxTree implements IntrospectSyntaxTree {
 
     @Override
     public SyntaxTree getDataModels(Module entityModule) throws BalException {
-        if (!entityModule.getEntityMap().values().isEmpty()) {
+        if (!entityModule.getEntityMap().isEmpty()) {
+            // Check if all entities have unsupported types
+            boolean allUnsupported = entityModule.getEntityMap().values().stream()
+                    .allMatch(Entity::containsUnsupportedTypes);
+
+            if (allUnsupported) {
+                throw new BalException("No valid entities found in the database. " +
+                        "All tables either lack primary keys or contain unsupported types.");
+            }
+
             return BalSyntaxUtils.generateModelSyntaxTree(entityModule);
         }
-        throw new BalException("No entities found in the database");
+        throw new BalException("No entities found in the database. " +
+                "The database may be empty or contain no accessible tables.");
     }
 
     @Override

persist-core/src/main/java/io/ballerina/persist/nodegenerator/syntax/sources/DbSyntaxTree.java

@@ -124,6 +124,13 @@ private static Client getClientObject(Module entityModule, ClientSyntax dbClient
             resource.addFunction(dbClientSyntax.getDeleteFunction(entity), true);
             resourceList.add(resource);
         }
+
+        // Check if all entities were filtered out
+        if (resourceList.isEmpty()) {
+            throw new BalException("No valid entities found for client generation. " +
+                    "All entities contain unsupported types or are missing primary keys.");
+        }
+
         resourceList.forEach(resource -> {
             resource.getFunctions().forEach(function -> {
                 clientObject.addMember(function, false);

persist-core/src/main/java/io/ballerina/persist/utils/ScriptRunner.java

@@ -147,9 +147,8 @@ public List<SqlTable> getSQLTables(String query) throws SQLException {
                 while (results.next()) {
                     tables.add(SqlTable.newBuilder(results.getString("table_name")).build());
                 }
-                if (tables.isEmpty()) {
-                    throw new SQLException("No tables found in the database.");
-                }
+                // Return empty list instead of throwing exception for empty databases
+                // The error is handled in the calling function
                 return tables;
             }
         } catch (SQLException e) {