Fix executeBatch in auto-commit mode

This change fixes the problem when connection is left in inconsistent
state when `executeBatch` throws constraint (or some other) error with
auto-commit enabled.

In duckdb#213 `executeBatch` was changed to effectively disable auto-commit
for the whole batch. In this case the rollback on error needs to be
handled inside `executeBatch` too.

Testing: new tests added that cover constrain violation with
`executeBatch`.

Fixes: duckdb#259

Author: staticlibs

src/main/java/org/duckdb/DuckDBPreparedStatement.java

@@ -645,11 +645,13 @@ public long[] executeLargeBatch() throws SQLException {
 
     private long[] executeBatchedPreparedStatement() throws SQLException {
         stmtRefLock.lock();
+        boolean tranStarted = false;
+        DuckDBConnection conn = this.conn;
         try {
             checkOpen();
             checkPrepared();
 
-            boolean tranStarted = startTransaction();
+            tranStarted = startTransaction();
 
             long[] updateCounts = new long[this.batchedParams.size()];
             for (int i = 0; i < this.batchedParams.size(); i++) {
@@ -664,17 +666,25 @@ private long[] executeBatchedPreparedStatement() throws SQLException {
             }
 
             return updateCounts;
+
+        } catch (SQLException e) {
+            if (tranStarted && conn.getAutoCommit()) {
+                conn.rollback();
+            }
+            throw e;
         } finally {
             stmtRefLock.unlock();
         }
     }
 
     private long[] executeBatchedStatements() throws SQLException {
         stmtRefLock.lock();
+        boolean tranStarted = false;
+        DuckDBConnection conn = this.conn;
         try {
             checkOpen();
 
-            boolean tranStarted = startTransaction();
+            tranStarted = startTransaction();
 
             long[] updateCounts = new long[this.batchedStatements.size()];
             for (int i = 0; i < this.batchedStatements.size(); i++) {
@@ -689,6 +699,12 @@ private long[] executeBatchedStatements() throws SQLException {
             }
 
             return updateCounts;
+
+        } catch (SQLException e) {
+            if (tranStarted && conn.getAutoCommit()) {
+                conn.rollback();
+            }
+            throw e;
         } finally {
             stmtRefLock.unlock();
         }

src/test/java/org/duckdb/TestBatch.java

@@ -4,6 +4,7 @@
 import static org.duckdb.test.Assertions.*;
 
 import java.sql.*;
+import java.util.Properties;
 
 public class TestBatch {
 
@@ -206,4 +207,102 @@ public static void test_statement_batch_rollback() throws Exception {
             }
         }
     }
+
+    public static void test_statement_batch_autocommit_constraint_violation() throws Exception {
+        try (Connection conn = DriverManager.getConnection(JDBC_URL)) {
+            assertTrue(conn.getAutoCommit());
+            try (Statement stmt = conn.createStatement()) {
+                stmt.execute("CREATE TABLE tab1 (col1 VARCHAR NOT NULL)");
+            }
+            try (Statement stmt = conn.createStatement()) {
+                stmt.addBatch("INSERT INTO tab1 VALUES('foo')");
+                stmt.addBatch("INSERT INTO tab1 VALUES(NULL)");
+                assertThrows(stmt::executeBatch, SQLException.class);
+            }
+            try (Statement stmt = conn.createStatement();
+                 ResultSet rs = stmt.executeQuery("SELECT count(*) FROM tab1")) {
+                rs.next();
+                assertEquals(rs.getLong(1), 0L);
+            }
+        }
+    }
+
+    public static void test_prepared_statement_batch_autocommit_constraint_violation() throws Exception {
+        try (Connection conn = DriverManager.getConnection(JDBC_URL)) {
+            assertTrue(conn.getAutoCommit());
+            try (Statement stmt = conn.createStatement()) {
+                stmt.execute("CREATE TABLE tab1 (col1 VARCHAR NOT NULL)");
+            }
+            try (PreparedStatement ps = conn.prepareStatement("INSERT INTO tab1 VALUES(?)")) {
+                ps.setString(1, "foo");
+                ps.addBatch();
+                ps.setString(1, null);
+                ps.addBatch();
+                assertThrows(ps::executeBatch, SQLException.class);
+            }
+            try (Statement stmt = conn.createStatement();
+                 ResultSet rs = stmt.executeQuery("SELECT count(*) FROM tab1")) {
+                rs.next();
+                assertEquals(rs.getLong(1), 0L);
+            }
+        }
+    }
+
+    public static void test_statement_batch_constraint_violation() throws Exception {
+        Properties config = new Properties();
+        config.put(DuckDBDriver.JDBC_AUTO_COMMIT, false);
+        try (Connection conn = DriverManager.getConnection(JDBC_URL, config)) {
+            assertFalse(conn.getAutoCommit());
+            try (Statement stmt = conn.createStatement()) {
+                stmt.execute("CREATE TABLE tab1 (col1 VARCHAR NOT NULL)");
+                conn.commit();
+            }
+            boolean thrown = false;
+            try (Statement stmt = conn.createStatement()) {
+                stmt.addBatch("INSERT INTO tab1 VALUES('foo')");
+                stmt.addBatch("INSERT INTO tab1 VALUES(NULL)");
+                stmt.executeBatch();
+                conn.commit();
+            } catch (SQLException e) {
+                thrown = true;
+                conn.rollback();
+            }
+            assertTrue(thrown);
+            try (Statement stmt = conn.createStatement();
+                 ResultSet rs = stmt.executeQuery("SELECT count(*) FROM tab1")) {
+                rs.next();
+                assertEquals(rs.getLong(1), 0L);
+            }
+        }
+    }
+
+    public static void test_prepared_statement_batch_constraint_violation() throws Exception {
+        Properties config = new Properties();
+        config.put(DuckDBDriver.JDBC_AUTO_COMMIT, false);
+        try (Connection conn = DriverManager.getConnection(JDBC_URL, config)) {
+            assertFalse(conn.getAutoCommit());
+            try (Statement stmt = conn.createStatement()) {
+                stmt.execute("CREATE TABLE tab1 (col1 VARCHAR NOT NULL)");
+                conn.commit();
+            }
+            boolean thrown = false;
+            try (PreparedStatement ps = conn.prepareStatement("INSERT INTO tab1 VALUES(?)")) {
+                ps.setString(1, "foo");
+                ps.addBatch();
+                ps.setString(1, null);
+                ps.addBatch();
+                ps.executeBatch();
+                conn.commit();
+            } catch (SQLException e) {
+                thrown = true;
+                conn.rollback();
+            }
+            assertTrue(thrown);
+            try (Statement stmt = conn.createStatement();
+                 ResultSet rs = stmt.executeQuery("SELECT count(*) FROM tab1")) {
+                rs.next();
+                assertEquals(rs.getLong(1), 0L);
+            }
+        }
+    }
 }