From f8149afb63b9a66e89119290c594b50e599f351a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Knut=20Olav=20L=C3=B8ite?= <koloite@gmail.com>
Date: Mon, 18 Jan 2021 00:38:46 +0100
Subject: [PATCH] fix: getting resultset metadata twice could skip row (#323)

* fix: getting resultset metadata twice could skip row

If the client application would call ResultSet#getMetaData() more than once
**before** calling ResultSet#next(), the ResultSet would skip a row when the
rows would be consumed.

Fixes #322

* test: add test for getMetaData twice
---
 .../cloud/spanner/jdbc/JdbcResultSet.java     |  2 +-
 .../cloud/spanner/jdbc/JdbcResultSetTest.java | 27 +++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/main/java/com/google/cloud/spanner/jdbc/JdbcResultSet.java b/src/main/java/com/google/cloud/spanner/jdbc/JdbcResultSet.java
index 3f10b0c1..c4ca6b5e 100644
--- a/src/main/java/com/google/cloud/spanner/jdbc/JdbcResultSet.java
+++ b/src/main/java/com/google/cloud/spanner/jdbc/JdbcResultSet.java
@@ -547,7 +547,7 @@ public InputStream getBinaryStream(String columnLabel) throws SQLException {
   @Override
   public JdbcResultSetMetaData getMetaData() throws SQLException {
     checkClosed();
-    if (isBeforeFirst()) {
+    if (isBeforeFirst() && !nextCalledForMetaData) {
       // do a call to next() on the underlying resultset to initialize metadata
       nextCalledForMetaData = true;
       nextCalledForMetaDataResult = spanner.next();
diff --git a/src/test/java/com/google/cloud/spanner/jdbc/JdbcResultSetTest.java b/src/test/java/com/google/cloud/spanner/jdbc/JdbcResultSetTest.java
index 9429288d..2ad4a6d4 100644
--- a/src/test/java/com/google/cloud/spanner/jdbc/JdbcResultSetTest.java
+++ b/src/test/java/com/google/cloud/spanner/jdbc/JdbcResultSetTest.java
@@ -25,6 +25,7 @@
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 import com.google.cloud.ByteArray;
 import com.google.cloud.Date;
@@ -802,6 +803,32 @@ public void testGetMetaData() throws SQLException {
     assertNotNull(metadata);
   }
 
+  @Test
+  public void testGetMetaDataBeforeNext() throws SQLException {
+    ResultSet spannerResultSet = mock(ResultSet.class);
+    when(spannerResultSet.next()).thenReturn(true, false);
+
+    JdbcResultSet resultSet = JdbcResultSet.of(spannerResultSet);
+    assertNotNull(resultSet.getMetaData());
+    assertTrue(resultSet.next());
+    assertFalse(resultSet.next());
+  }
+
+  @Test
+  public void testGetMetaDataTwiceBeforeNext() throws SQLException {
+    ResultSet spannerResultSet = mock(ResultSet.class);
+    when(spannerResultSet.next()).thenReturn(true, false);
+
+    JdbcResultSet resultSet = JdbcResultSet.of(spannerResultSet);
+    assertNotNull(resultSet.getMetaData());
+    assertNotNull(resultSet.getMetaData());
+
+    // This would have returned false before the fix in
+    // https://github.com/googleapis/java-spanner-jdbc/pull/323
+    assertTrue(resultSet.next());
+    assertFalse(resultSet.next());
+  }
+
   @Test
   public void testFindColumn() throws SQLException {
     assertEquals(2, subject.findColumn(STRING_COL_NOT_NULL));