fixed isLast for an empty set

Author: chernser

jdbc-v2/src/main/java/com/clickhouse/jdbc/ResultSetImpl.java

@@ -545,7 +545,7 @@ public boolean isFirst() throws SQLException {
     @Override
     public boolean isLast() throws SQLException {
         checkClosed();
-        return !reader.hasNext() && rowPos != AFTER_LAST;
+        return !reader.hasNext() && rowPos != AFTER_LAST && rowPos != BEFORE_FIRST;
     }
 
     @Override

jdbc-v2/src/main/java/com/clickhouse/jdbc/StatementImpl.java

@@ -131,10 +131,10 @@ protected ResultSetImpl executeQueryImpl(String sql, QuerySettings settings) thr
         // release before this one completes.
         if (resultSetAutoClose) {
             closeCurrentResultSet();
-            // There is a feature `closeOnComplete` that dictate closing statement when all
+            // There is a feature `closeOnComplete` that dictates closing the statement when all
             // result sets are closed. Call to `closeCurrentResultSet` will trigger this statement
-            // closure. But it should not happen because this was introduces instead of spec and will be remove in future/
-            // So we need make this statement open again because we going to create a new result set.
+            // closure. But it should not happen because this was introduces instead of spec and will be removed in the future.
+            // So we need to make this statement open again because we're going to create a new result set.
             this.closed = false;
         }
 
@@ -370,7 +370,7 @@ public int getFetchDirection() throws SQLException {
     public void setFetchSize(int rows) throws SQLException {
         ensureOpen();
         if (rows < 0) {
-            throw new SQLException("rows should be greater than 0.");
+            throw new SQLException("rows should be greater or equal to 0.");
         }
         this.fetchSize = rows;
     }

jdbc-v2/src/test/java/com/clickhouse/jdbc/ResultSetImplTest.java

@@ -241,7 +241,22 @@ public void testCursorPosition() throws SQLException {
                 Assert.assertFalse(rs.isFirst());
                 Assert.assertFalse(rs.isLast());
                 Assert.assertEquals(rs.getRow(), 0);
+            }
 
+            try (ResultSet rs = stmt.executeQuery("select 1 LIMIT 0")) {
+                Assert.assertTrue(rs.isBeforeFirst());
+                Assert.assertFalse(rs.isAfterLast());
+                Assert.assertFalse(rs.isFirst());
+                Assert.assertFalse(rs.isLast());
+                Assert.assertEquals(rs.getRow(), 0);
+
+                Assert.assertFalse(rs.next());
+
+                Assert.assertFalse(rs.isBeforeFirst()); // we stepped over the end
+                Assert.assertTrue(rs.isAfterLast()); // we stepped over the end
+                Assert.assertFalse(rs.isFirst());
+                Assert.assertFalse(rs.isLast());
+                Assert.assertEquals(rs.getRow(), 0);
             }
         }
     }