fix: null pointer exception from PgResultSetMetaData when there's no …

…column metadata (#1615)

* fix all possible NPE in PgResultSetMetaData when there's column metadata

pgjdbc/src/main/java/org/postgresql/jdbc/PgResultSetMetaData.java

@@ -113,7 +113,8 @@ public boolean isCurrency(int column) throws SQLException {
   public int isNullable(int column) throws SQLException {
     fetchFieldMetaData();
     Field field = getField(column);
-    return field.getMetadata().nullable;
+    FieldMetadata metadata = field.getMetadata();
+    return metadata == null ? ResultSetMetaData.columnNullable : metadata.nullable;
   }
 
   /**
@@ -151,7 +152,8 @@ public String getBaseColumnName(int column) throws SQLException {
       return "";
     }
     fetchFieldMetaData();
-    return field.getMetadata().columnName;
+    FieldMetadata metadata = field.getMetadata();
+    return metadata == null ? "" : metadata.columnName;
   }
 
   public String getSchemaName(int column) throws SQLException {
@@ -268,7 +270,8 @@ private void fetchFieldMetaData() throws SQLException {
   public String getBaseSchemaName(int column) throws SQLException {
     fetchFieldMetaData();
     Field field = getField(column);
-    return field.getMetadata().schemaName;
+    FieldMetadata metadata = field.getMetadata();
+    return metadata == null ? "" : metadata.schemaName;
   }
 
   public int getPrecision(int column) throws SQLException {
@@ -288,7 +291,8 @@ public String getTableName(int column) throws SQLException {
   public String getBaseTableName(int column) throws SQLException {
     fetchFieldMetaData();
     Field field = getField(column);
-    return field.getMetadata().tableName;
+    FieldMetadata metadata = field.getMetadata();
+    return metadata == null ? "" : metadata.tableName;
   }
 
   /**

pgjdbc/src/test/java/org/postgresql/jdbc/NoColumnMetadataIssue1613.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2019, PostgreSQL Global Development Group
+ * See the LICENSE file in the project root for more information.
+ */
+
+package org.postgresql.jdbc;
+
+import static org.junit.Assert.assertTrue;
+
+import org.postgresql.test.TestUtil;
+import org.postgresql.test.jdbc2.BaseTest4;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.sql.ResultSet;
+import java.sql.Statement;
+
+/**
+ * If the SQL query has no column metadata, the driver shouldn't break by a null pointer exception.
+ * It should return the result correctly.
+ *
+ * @author Ivy (ivyyiyideng@gmail.com)
+ *
+ */
+public class NoColumnMetadataIssue1613 extends BaseTest4 {
+  @Override
+  @Before
+  public void setUp() throws Exception {
+    super.setUp();
+    TestUtil.createTempTable(con, "test_no_column_metadata","id int");
+  }
+
+  @Test
+  public void shouldBeNoNPE() throws Exception {
+    Statement statement = con.createStatement();
+    statement.executeQuery("INSERT INTO test_no_column_metadata values (1)");
+    ResultSet rs = statement.executeQuery("SELECT x FROM test_no_column_metadata x");
+    assertTrue(rs.next());
+  }
+}