/*
 * Copyright 2004-2018 H2 Group. Multiple-Licensed under the MPL 2.0,
 * and the EPL 1.0 (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2.test.store;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.StringReader;
import java.math.BigDecimal;
import java.nio.channels.FileChannel;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Savepoint;
import java.sql.Statement;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import org.h2.api.ErrorCode;
import org.h2.engine.Constants;
import org.h2.engine.Database;
import org.h2.jdbc.JdbcConnection;
import org.h2.mvstore.MVMap;
import org.h2.mvstore.MVStore;
import org.h2.mvstore.tx.TransactionStore;
import org.h2.store.fs.FileUtils;
import org.h2.test.TestBase;
import org.h2.test.TestDb;
import org.h2.tools.Recover;
import org.h2.tools.Restore;
import org.h2.util.JdbcUtils;
import org.h2.util.Task;

/**
 * Tests the MVStore in a database.
 */
public class TestMVTableEngine extends TestDb {

    /**
     * Run just this test.
     *
     * @param a ignored
     */
    public static void main(String... a) throws Exception {
        TestBase.createCaller().init().test();
    }

    @Override
    public void test() throws Exception {
        if (!config.mvStore) {
            return;
        }
        testLobCopy();
        testLobReuse();
        testShutdownDuringLobCreation();
        testLobCreationThenShutdown();
        testManyTransactions();
        testAppendOnly();
        testLowRetentionTime();
        testOldAndNew();
        testTemporaryTables();
        testUniqueIndex();
        testSecondaryIndex();
        testGarbageCollectionForLOB();
        testSpatial();
        testCount();
        testMinMaxWithNull();
        testTimeout();
        testExplainAnalyze();
        testTransactionLogUsuallyNotStored();
        testShrinkDatabaseFile();
        testTwoPhaseCommit();
        testRecover();
        testSeparateKey();
        testRollback();
        testRollbackAfterCrash();
        testReferentialIntegrity();
        testWriteDelay();
        testAutoCommit();
        testReopen();
        testBlob();
        testEncryption();
        testReadOnly();
        testReuseDiskSpace();
        testDataTypes();
        testSimple();
        if (!config.travis) {
            testReverseDeletePerformance();
        }
    }

    private void testLobCopy() throws Exception {
        deleteDb(getTestName());
        Connection conn = getConnection(getTestName());
        Statement stat = conn.createStatement();
        stat.execute("create table test(id int primary key, data clob)");
        stat = conn.createStatement();
        stat.execute("insert into test(id, data) values(2, space(300))");
        stat.execute("insert into test(id, data) values(1, space(300))");
        stat.execute("alter table test add column x int");
        if (!config.memory) {
            conn.close();
            conn = getConnection(getTestName());
        }
        stat = conn.createStatement();
        ResultSet rs = stat.executeQuery("select data from test");
        while (rs.next()) {
            rs.getString(1);
        }
        conn.close();
    }

    private void testLobReuse() throws Exception {
        deleteDb(getTestName());
        Connection conn1 = getConnection(getTestName());
        Statement stat = conn1.createStatement();
        stat.execute("create table test(id identity primary key, lob clob)");
        byte[] buffer = new byte[8192];
        for (int i = 0; i < 20; i++) {
            Connection conn2 = getConnection(getTestName());
            stat = conn2.createStatement();
            stat.execute("insert into test(lob) select space(1025) from system_range(1, 10)");
            stat.execute("delete from test where random() > 0.5");
            ResultSet rs = conn2.createStatement().executeQuery(
                    "select lob from test");
            while (rs.next()) {
                InputStream is = rs.getBinaryStream(1);
                while (is.read(buffer) != -1) {
                    // ignore
                }
            }
            conn2.close();
        }
        conn1.close();
    }

    private void testShutdownDuringLobCreation() throws Exception {
        if (config.memory) {
            return;
        }
        deleteDb(getTestName());
        Connection conn = getConnection(getTestName());
        Statement stat = conn.createStatement();
        stat.execute("create table test(data clob) as select space(10000)");
        final PreparedStatement prep = conn
                .prepareStatement("set @lob = ?");
        final AtomicBoolean end = new AtomicBoolean();
        Task t = new Task() {

            @Override
            public void call() throws Exception {
                prep.setBinaryStream(1, new InputStream() {

                    int len;

                    @Override
                    public int read() throws IOException {
                        if (len++ < 1024 * 1024 * 4) {
                            return 0;
                        }
                        end.set(true);
                        while (!stop) {
                            try {
                                Thread.sleep(1);
                            } catch (InterruptedException e) {
                                // ignore
                            }
                        }
                        return -1;
                    }
                }    , -1);
            }
        };
        t.execute();
        while (!end.get()) {
            Thread.sleep(1);
        }
        stat.execute("checkpoint");
        stat.execute("shutdown immediately");
        Exception ex = t.getException();
        assertNotNull(ex);
        try {
            conn.close();
        } catch (Exception e) {
            // ignore
        }
        conn = getConnection(getTestName());
        stat = conn.createStatement();
        stat.execute("shutdown defrag");
        try {
            conn.close();
        } catch (Exception e) {
            // ignore
        }
        conn = getConnection(getTestName());
        stat = conn.createStatement();
        ResultSet rs = stat.executeQuery("select * " +
                "from information_schema.settings " +
                "where name = 'info.PAGE_COUNT'");
        rs.next();
        int pages = rs.getInt(2);
        // only one lob should remain (but it is small and compressed)
        assertTrue("p:" + pages, pages < 4);
        conn.close();
    }

    private void testLobCreationThenShutdown() throws Exception {
        if (config.memory) {
            return;
        }
        deleteDb(getTestName());
        Connection conn = getConnection(getTestName());
        Statement stat = conn.createStatement();
        stat.execute("create table test(id identity, data clob)");
        PreparedStatement prep = conn
                .prepareStatement("insert into test values(?, ?)");
        for (int i = 0; i < 9; i++) {
            prep.setInt(1, i);
            int size = i * i * i * i * 1024;
            prep.setCharacterStream(2, new StringReader(new String(
                    new char[size])));
            prep.execute();
        }
        stat.execute("shutdown immediately");
        try {
            conn.close();
        } catch (Exception e) {
            // ignore
        }
        conn = getConnection(getTestName());
        stat = conn.createStatement();
        stat.execute("drop all objects");
        stat.execute("shutdown defrag");
        try {
            conn.close();
        } catch (Exception e) {
            // ignore
        }
        conn = getConnection(getTestName());
        stat = conn.createStatement();
        ResultSet rs = stat.executeQuery("select * " +
                "from information_schema.settings " +
                "where name = 'info.PAGE_COUNT'");
        rs.next();
        int pages = rs.getInt(2);
        // no lobs should remain
        assertTrue("p:" + pages, pages < 4);
        conn.close();
    }

    private void testManyTransactions() throws Exception {
        deleteDb(getTestName());
        Connection conn = getConnection(getTestName());
        Statement stat = conn.createStatement();
        stat.execute("create table test()");
        conn.setAutoCommit(false);
        stat.execute("insert into test values()");

        Connection conn2 = getConnection(getTestName());
        Statement stat2 = conn2.createStatement();
        for (long i = 0; i < 100000; i++) {
            stat2.execute("insert into test values()");
        }
        conn2.close();
        conn.close();
    }

    private void testAppendOnly() throws Exception {
        if (config.memory) {
            return;
        }
        deleteDb(getTestName());
        Connection conn = getConnection(getTestName());
        Statement stat = conn.createStatement();
        stat.execute("set retention_time 0");
        for (int i = 0; i < 10; i++) {
            stat.execute("create table dummy" + i +
                    " as select x, space(100) from system_range(1, 1000)");
            stat.execute("checkpoint");
        }
        stat.execute("create table test as select x from system_range(1, 1000)");
        conn.close();
        String fileName = getBaseDir() + "/" + getTestName() + Constants.SUFFIX_MV_FILE;
        long fileSize = FileUtils.size(fileName);

        conn = getConnection(
                getTestName() + ";reuse_space=false");
        stat = conn.createStatement();
        stat.execute("set retention_time 0");
        for (int i = 0; i < 10; i++) {
            stat.execute("drop table dummy" + i);
            stat.execute("checkpoint");
        }
        stat.execute("alter table test alter column x rename to y");
        stat.execute("select y from test where 1 = 0");
        stat.execute("create table test2 as select x from system_range(1, 1000)");
        conn.close();

        FileChannel fc = FileUtils.open(fileName, "rw");
        // undo all changes
        fc.truncate(fileSize);
        fc.close();

        conn = getConnection(getTestName());
        stat = conn.createStatement();
        stat.execute("select * from dummy0 where 1 = 0");
        stat.execute("select * from dummy9 where 1 = 0");
        stat.execute("select x from test where 1 = 0");
        conn.close();
    }

    private void testLowRetentionTime() throws SQLException {
        deleteDb(getTestName());
        Connection conn = getConnection(
                getTestName() + ";RETENTION_TIME=10;WRITE_DELAY=10");
        Statement stat = conn.createStatement();
        Connection conn2 = getConnection(getTestName());
        Statement stat2 = conn2.createStatement();
        stat.execute("create alias sleep as " +
                "$$void sleep(int ms) throws Exception { Thread.sleep(ms); }$$");
        stat.execute("create table test(id identity, name varchar) " +
                "as select x, 'Init' from system_range(0, 1999)");
        for (int i = 0; i < 10; i++) {
            stat.execute("insert into test values(null, 'Hello')");
            // create and delete a large table: this will force compaction
            stat.execute("create table temp(id identity, name varchar) as " +
                    "select x, space(1000000) from system_range(0, 10)");
            stat.execute("drop table temp");
        }
        ResultSet rs = stat2
                .executeQuery("select *, sleep(1) from test order by id");
        for (int i = 0; i < 2000 + 10; i++) {
            assertTrue(rs.next());
            assertEquals(i, rs.getInt(1));
        }
        assertFalse(rs.next());
        conn2.close();
        conn.close();
    }

    private void testOldAndNew() throws SQLException {
        if (config.memory) {
            return;
        }
        Connection conn;
        deleteDb(getTestName());
        String urlOld = getURL(getTestName() + ";MV_STORE=FALSE", true);
        String urlNew = getURL(getTestName() + ";MV_STORE=TRUE", true);
        String url = getURL(getTestName(), true);

        conn = getConnection(urlOld);
        conn.createStatement().execute("create table test_old(id int)");
        conn.close();
        conn = getConnection(url);
        conn.createStatement().execute("select * from test_old");
        conn.close();
        conn = getConnection(urlNew);
        conn.createStatement().execute("create table test_new(id int)");
        conn.close();
        conn = getConnection(url);
        conn.createStatement().execute("select * from test_new");
        conn.close();
        conn = getConnection(urlOld);
        conn.createStatement().execute("select * from test_old");
        conn.close();
        conn = getConnection(urlNew);
        conn.createStatement().execute("select * from test_new");
        conn.close();
    }

    private void testTemporaryTables() throws SQLException {
        Connection conn;
        Statement stat;
        deleteDb(getTestName());
        String url = getTestName() + ";MV_STORE=TRUE";
        url = getURL(url, true);
        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("set max_memory_rows 100");
        stat.execute("create table t1 as select x from system_range(1, 200)");
        stat.execute("create table t2 as select x from system_range(1, 200)");
        for (int i = 0; i < 20; i++) {
            // this will create temporary results that
            // internally use temporary tables, which are not all closed
            stat.execute("select count(*) from t1 where t1.x in (select t2.x from t2)");
        }
        conn.close();
        conn = getConnection(url);
        stat = conn.createStatement();
        for (int i = 0; i < 20; i++) {
            stat.execute("create table a" + i + "(id int primary key)");
            ResultSet rs = stat.executeQuery("select count(*) from a" + i);
            rs.next();
            assertEquals(0, rs.getInt(1));
        }
        conn.close();
    }

    private void testUniqueIndex() throws SQLException {
        Connection conn;
        Statement stat;
        deleteDb(getTestName());
        String url = getTestName() + ";MV_STORE=TRUE";
        url = getURL(url, true);
        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("create table test as select x, 0 from system_range(1, 5000)");
        stat.execute("create unique index on test(x)");
        ResultSet rs = stat.executeQuery("select * from test where x=1");
        assertTrue(rs.next());
        assertFalse(rs.next());
        conn.close();
    }

    private void testSecondaryIndex() throws SQLException {
        Connection conn;
        Statement stat;
        deleteDb(getTestName());
        String url = getTestName() + ";MV_STORE=TRUE";
        url = getURL(url, true);
        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("create table test(id int)");
        int size = 8 * 1024;
        stat.execute("insert into test select mod(x * 111, " + size + ") " +
                "from system_range(1, " + size + ")");
        stat.execute("create index on test(id)");
        ResultSet rs = stat.executeQuery(
                "select count(*) from test inner join " +
                "system_range(1, " + size + ") where " +
                "id = mod(x * 111, " + size + ")");
        rs.next();
        assertEquals(size, rs.getInt(1));
        conn.close();
    }

    private void testGarbageCollectionForLOB() throws SQLException {
        if (config.memory) {
            return;
        }
        Connection conn;
        Statement stat;
        deleteDb(getTestName());
        String url = getTestName() + ";MV_STORE=TRUE";
        url = getURL(url, true);
        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("create table test(id int, data blob)");
        stat.execute("insert into test select x, repeat('0', 10000) " +
                "from system_range(1, 10)");
        stat.execute("drop table test");
        stat.execute("create table test2(id int, data blob)");
        PreparedStatement prep = conn.prepareStatement(
                "insert into test2 values(?, ?)");
        prep.setInt(1, 1);
        assertThrows(ErrorCode.IO_EXCEPTION_1, prep).
            setBinaryStream(1, createFailingStream(new IOException()));
        prep.setInt(1, 2);
        assertThrows(ErrorCode.IO_EXCEPTION_1, prep).
            setBinaryStream(1, createFailingStream(new IllegalStateException()));
        conn.close();
        MVStore s = MVStore.open(getBaseDir()+ "/" + getTestName() + ".mv.db");
        assertTrue(s.hasMap("lobData"));
        MVMap<Long, byte[]> lobData = s.openMap("lobData");
        assertEquals(0, lobData.sizeAsLong());
        assertTrue(s.hasMap("lobMap"));
        MVMap<Long, byte[]> lobMap = s.openMap("lobMap");
        assertEquals(0, lobMap.sizeAsLong());
        assertTrue(s.hasMap("lobRef"));
        MVMap<Long, byte[]> lobRef = s.openMap("lobRef");
        assertEquals(0, lobRef.sizeAsLong());
        s.close();
    }

    private void testSpatial() throws SQLException {
        Connection conn;
        Statement stat;
        deleteDb(getTestName());
        String url = getTestName() + ";MV_STORE=TRUE";
        url = getURL(url, true);
        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("call rand(1)");
        stat.execute("create table coordinates as select rand()*50 x, " +
                "rand()*50 y from system_range(1, 5000)");
        stat.execute("create table test(id identity, data geometry)");
        stat.execute("create spatial index on test(data)");
        stat.execute("insert into test(data) select 'polygon(('||" +
                "(1+x)||' '||(1+y)||', '||(2+x)||' '||(2+y)||', "+
                "'||(3+x)||' '||(1+y)||', '||(1+x)||' '||(1+y)||'))' from coordinates;");
        conn.close();
    }

    private void testCount() throws Exception {
        if (config.memory) {
            return;
        }

        Connection conn;
        Connection conn2;
        Statement stat;
        Statement stat2;
        deleteDb(getTestName());
        String url = getTestName() + ";MV_STORE=TRUE";
        url = getURL(url, true);
        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("create table test(id int)");
        stat.execute("create table test2(id int)");
        stat.execute("insert into test select x from system_range(1, 10000)");
        conn.close();

        ResultSet rs;
        String plan;

        conn2 = getConnection(url);
        stat2 = conn2.createStatement();
        rs = stat2.executeQuery("explain analyze select count(*) from test");
        rs.next();
        plan = rs.getString(1);
        assertTrue(plan, plan.indexOf("reads:") < 0);

        conn = getConnection(url);
        stat = conn.createStatement();
        conn.setAutoCommit(false);
        stat.execute("insert into test select x from system_range(1, 1000)");
        rs = stat.executeQuery("select count(*) from test");
        rs.next();
        assertEquals(11000, rs.getInt(1));

        // not yet committed
        rs = stat2.executeQuery("explain analyze select count(*) from test");
        rs.next();
        plan = rs.getString(1);
        // transaction log is small, so no need to read the table
        assertTrue(plan, plan.indexOf("reads:") < 0);
        rs = stat2.executeQuery("select count(*) from test");
        rs.next();
        assertEquals(10000, rs.getInt(1));

        stat.execute("insert into test2 select x from system_range(1, 11000)");
        rs = stat2.executeQuery("explain analyze select count(*) from test");
        rs.next();
        plan = rs.getString(1);
        // transaction log is larger than the table, so read the table
        assertContains(plan, "reads:");
        rs = stat2.executeQuery("select count(*) from test");
        rs.next();
        assertEquals(10000, rs.getInt(1));

        conn2.close();
        conn.close();
    }

    private void testMinMaxWithNull() throws Exception {
        Connection conn;
        Connection conn2;
        Statement stat;
        Statement stat2;
        deleteDb(getTestName());
        String url = getTestName() + ";MV_STORE=TRUE";
        url = getURL(url, true);
        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("create table test(data int)");
        stat.execute("create index on test(data)");
        stat.execute("insert into test values(null), (2)");
        conn2 = getConnection(url);
        stat2 = conn2.createStatement();
        conn.setAutoCommit(false);
        conn2.setAutoCommit(false);
        stat.execute("insert into test values(1)");
        ResultSet rs;
        rs = stat.executeQuery("select min(data) from test");
        rs.next();
        assertEquals(1, rs.getInt(1));
        rs = stat2.executeQuery("select min(data) from test");
        rs.next();
        // not yet committed
        assertEquals(2, rs.getInt(1));
        conn2.close();
        conn.close();
    }

    private void testTimeout() throws Exception {
        Connection conn;
        Connection conn2;
        Statement stat;
        Statement stat2;
        deleteDb(getTestName());
        String url = getTestName() + ";MV_STORE=TRUE";
        url = getURL(url, true);
        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("create table test(id identity, name varchar)");
        conn2 = getConnection(url);
        stat2 = conn2.createStatement();
        conn.setAutoCommit(false);
        conn2.setAutoCommit(false);
        stat.execute("insert into test values(1, 'Hello')");
        assertThrows(ErrorCode.LOCK_TIMEOUT_1, stat2).
                execute("insert into test values(1, 'Hello')");
        conn2.close();
        conn.close();
    }

    private void testExplainAnalyze() throws Exception {
        if (config.memory) {
            return;
        }
        Connection conn;
        Statement stat;
        deleteDb(getTestName());
        String url = getTestName() + ";MV_STORE=TRUE";
        url = getURL(url, true);
        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("create table test(id identity, name varchar) as " +
                "select x, space(1000) from system_range(1, 1000)");
        ResultSet rs;
        conn.close();
        conn = getConnection(url);
        stat = conn.createStatement();
        rs = stat.executeQuery("explain analyze select * from test");
        rs.next();
        String plan = rs.getString(1);
        // expect about 1000 reads
        String readCount = plan.substring(plan.indexOf("reads: "));
        readCount = readCount.substring("reads: ".length(), readCount.indexOf('\n'));
        int rc = Integer.parseInt(readCount);
        assertTrue(plan, rc >= 60 && rc <= 70);
//        assertTrue(plan, rc >= 1000 && rc <= 1200);
        conn.close();
    }

    private void testTransactionLogUsuallyNotStored() throws Exception {
        Connection conn;
        Statement stat;
        // we expect the transaction log is empty in at least some of the cases
        for (int test = 0; test < 5; test++) {
            deleteDb(getTestName());
            String url = getTestName() + ";MV_STORE=TRUE";
            url = getURL(url, true);
            conn = getConnection(url);
            stat = conn.createStatement();
            stat.execute("create table test(id identity, name varchar)");
            conn.setAutoCommit(false);
            PreparedStatement prep = conn.prepareStatement(
                    "insert into test(name) values(space(10000))");
            for (int j = 0; j < 100; j++) {
                for (int i = 0; i < 100; i++) {
                    prep.execute();
                }
                conn.commit();
            }
            stat.execute("shutdown immediately");
            JdbcUtils.closeSilently(conn);

            String file = getBaseDir() + "/" + getTestName() +
                    Constants.SUFFIX_MV_FILE;

            MVStore store = MVStore.open(file);
            TransactionStore t = new TransactionStore(store);
            t.init();
            int openTransactions = t.getOpenTransactions().size();
            store.close();
            if (openTransactions == 0) {
                return;
            }
        }
        fail("transaction log was never empty");
    }

    private void testShrinkDatabaseFile() throws Exception {
        if (config.memory) {
            return;
        }
        deleteDb(getTestName());
        String dbName = getTestName() + ";MV_STORE=TRUE";
        Connection conn;
        Statement stat;
        long maxSize = 0;
        // by default, the database does not shrink for 45 seconds
        int retentionTime = 45000;
        for (int i = 0; i < 20; i++) {
            // the first 10 times, keep the default retention time
            // then switch to 0, at which point the database file
            // should stop to grow
            conn = getConnection(dbName);
            stat = conn.createStatement();
            if (i == 10) {
                stat.execute("set retention_time 0");
                retentionTime = 0;
            }
            ResultSet rs = stat.executeQuery(
                    "select value from information_schema.settings " +
                    "where name='RETENTION_TIME'");
            assertTrue(rs.next());
            assertEquals(retentionTime, rs.getInt(1));
            stat.execute("create table test(id int primary key, data varchar)");
            stat.execute("insert into test select x, space(100) " +
                    "from system_range(1, 1000)");
            // this table is kept
            if (i < 10) {
                stat.execute("create table test" + i +
                        "(id int primary key, data varchar) " +
                        "as select x, space(10) from system_range(1, 100)");
            }
            // force writing the chunk
            stat.execute("checkpoint");
            // drop the table - but the chunk is still used
            stat.execute("drop table test");
            stat.execute("checkpoint");
            stat.execute("shutdown immediately");
            try {
                conn.close();
            } catch (Exception e) {
                // ignore
            }
            String fileName = getBaseDir() + "/" + getTestName()
                    + Constants.SUFFIX_MV_FILE;
            long size = FileUtils.size(fileName);
            if (i < 10) {
                maxSize = (int) (Math.max(size, maxSize) * 1.2);
            } else if (size > maxSize) {
                fail(i + " size: " + size + " max: " + maxSize);
            }
        }
        long sizeOld = FileUtils.size(getBaseDir() + "/" + getTestName()
                + Constants.SUFFIX_MV_FILE);
        conn = getConnection(dbName);
        stat = conn.createStatement();
        stat.execute("shutdown compact");
        conn.close();
        long sizeNew = FileUtils.size(getBaseDir() + "/" + getTestName()
                + Constants.SUFFIX_MV_FILE);
        println("new: " + sizeNew + " old: " + sizeOld);
//        assertTrue("new: " + sizeNew + " old: " + sizeOld, sizeNew < sizeOld);
    }

    private void testTwoPhaseCommit() throws Exception {
        if (config.memory) {
            return;
        }
        Connection conn;
        Statement stat;
        deleteDb(getTestName());
        String url = getTestName() + ";MV_STORE=TRUE";
        url = getURL(url, true);
        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("create table test(id int primary key, name varchar)");
        stat.execute("set write_delay 0");
        conn.setAutoCommit(false);
        stat.execute("insert into test values(1, 'Hello')");
        stat.execute("prepare commit test_tx");
        stat.execute("shutdown immediately");
        JdbcUtils.closeSilently(conn);

        conn = getConnection(url);
        stat = conn.createStatement();
        ResultSet rs;
        rs = stat.executeQuery("select * from information_schema.in_doubt");
        assertTrue(rs.next());
        stat.execute("commit transaction test_tx");
        rs = stat.executeQuery("select * from test");
        assertTrue(rs.next());
        conn.close();
    }

    private void testRecover() throws Exception {
        if (config.memory) {
            return;
        }
        Connection conn;
        Statement stat;
        deleteDb(getTestName());
        String url = getTestName() + ";MV_STORE=TRUE";
        url = getURL(url, true);
        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("create table test(id int primary key, name varchar)");
        stat.execute("insert into test values(1, 'Hello')");
        stat.execute("create table test2(name varchar)");
        stat.execute("insert into test2 values('Hello World')");
        conn.close();

        Recover.execute(getBaseDir(), getTestName());
        deleteDb(getTestName());
        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("runscript from '" + getBaseDir() + "/" + getTestName()+ ".h2.sql'");
        ResultSet rs;
        rs = stat.executeQuery("select * from test");
        assertTrue(rs.next());
        assertEquals(1, rs.getInt(1));
        assertEquals("Hello", rs.getString(2));
        rs = stat.executeQuery("select * from test2");
        assertTrue(rs.next());
        assertEquals("Hello World", rs.getString(1));
        conn.close();
    }

    private void testRollback() throws Exception {
        Connection conn;
        Statement stat;
        deleteDb(getTestName());
        String url = getTestName() + ";MV_STORE=TRUE";
        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("create table test(id identity)");
        conn.setAutoCommit(false);
        stat.execute("insert into test values(1)");
        stat.execute("delete from test");
        conn.rollback();
        conn.close();
    }

    private void testSeparateKey() throws Exception {
        if (config.memory) {
            return;
        }
        Connection conn;
        Statement stat;
        deleteDb(getTestName());
        String url = getTestName() + ";MV_STORE=TRUE";

        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("create table a(id int)");
        stat.execute("insert into a values(1)");
        stat.execute("insert into a values(1)");

        stat.execute("create table test(id int not null) as select 100");
        stat.execute("create primary key on test(id)");
        ResultSet rs = stat.executeQuery("select * from test where id = 100");
        assertTrue(rs.next());
        conn.close();

        conn = getConnection(url);
        stat = conn.createStatement();
        rs = stat.executeQuery("select * from test where id = 100");
        assertTrue(rs.next());
        conn.close();
    }

    private void testRollbackAfterCrash() throws Exception {
        if (config.memory) {
            return;
        }
        Connection conn;
        Statement stat;
        deleteDb(getTestName());
        String url = getTestName() + ";MV_STORE=TRUE";
        String url2 = getTestName() + "2;MV_STORE=TRUE";

        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("create table test(id int)");
        stat.execute("insert into test values(0)");
        stat.execute("set write_delay 0");
        conn.setAutoCommit(false);
        stat.execute("insert into test values(1)");
        stat.execute("shutdown immediately");
        JdbcUtils.closeSilently(conn);

        conn = getConnection(url);
        stat = conn.createStatement();
        ResultSet rs = stat.executeQuery("select row_count_estimate " +
                "from information_schema.tables where table_name='TEST'");
        rs.next();
        assertEquals(1, rs.getLong(1));
        stat.execute("drop table test");

        stat.execute("create table test(id int primary key, data clob)");
        stat.execute("insert into test values(1, space(10000))");
        conn.setAutoCommit(false);
        stat.execute("delete from test");
        stat.execute("checkpoint");
        stat.execute("shutdown immediately");
        JdbcUtils.closeSilently(conn);

        conn = getConnection(url);
        stat = conn.createStatement();
        rs = stat.executeQuery("select * from test");
        assertTrue(rs.next());
        stat.execute("drop all objects delete files");
        conn.close();

        conn = getConnection(url);
        stat = conn.createStatement();
        stat.execute("create table test(id int primary key, name varchar)");
        stat.execute("create index idx_name on test(name, id)");
        stat.execute("insert into test select x, x || space(200 * x) " +
                "from system_range(1, 10)");
        conn.setAutoCommit(false);
        stat.execute("delete from test where id > 5");
        stat.execute("backup to '" + getBaseDir() + "/" + getTestName() + ".zip'");
        conn.rollback();
        Restore.execute(getBaseDir() + "/" +getTestName() + ".zip",
                getBaseDir(), getTestName() + "2");
        Connection conn2;
        conn2 = getConnection(url2);
        conn.close();
        conn2.close();

    }

    private void testReferentialIntegrity() throws Exception {
        Connection conn;
        Statement stat;
        deleteDb(getTestName());
        conn = getConnection(getTestName() + ";MV_STORE=TRUE");

        stat = conn.createStatement();
        stat.execute("create table test(id int, parent int " +
                "references test(id) on delete cascade)");
        stat.execute("insert into test values(0, 0)");
        stat.execute("delete from test");
        stat.execute("drop table test");

        stat.execute("create table parent(id int, name varchar)");
        stat.execute("create table child(id int, parentid int, " +
        "foreign key(parentid) references parent(id))");
        stat.execute("insert into parent values(1, 'mary'), (2, 'john')");
        stat.execute("insert into child values(10, 1), (11, 1), (20, 2), (21, 2)");
        stat.execute("update parent set name = 'marc' where id = 1");
        stat.execute("merge into parent key(id) values(1, 'marcy')");
        stat.execute("drop table parent, child");

        stat.execute("create table test(id identity, parent bigint, " +
                "foreign key(parent) references(id))");
        stat.execute("insert into test values(0, 0), (1, NULL), " +
                "(2, 1), (3, 3), (4, 3)");
        stat.execute("drop table test");

        stat.execute("create table parent(id int)");
        stat.execute("create table child(pid int)");
        stat.execute("insert into parent values(1)");
        stat.execute("insert into child values(2)");
        try {
            stat.execute("alter table child add constraint cp " +
                    "foreign key(pid) references parent(id)");
            fail();
        } catch (SQLException e) {
            assertEquals(
                    ErrorCode.REFERENTIAL_INTEGRITY_VIOLATED_PARENT_MISSING_1,
                    e.getErrorCode());
        }
        stat.execute("update child set pid=1");
        stat.execute("drop table child, parent");

        stat.execute("create table parent(id int)");
        stat.execute("create table child(pid int)");
        stat.execute("insert into parent values(1)");
        stat.execute("insert into child values(2)");
        try {
            stat.execute("alter table child add constraint cp " +
                        "foreign key(pid) references parent(id)");
            fail();
        } catch (SQLException e) {
            assertEquals(
                    ErrorCode.REFERENTIAL_INTEGRITY_VIOLATED_PARENT_MISSING_1,
                    e.getErrorCode());
        }
        stat.execute("drop table child, parent");

        stat.execute("create table test(id identity, parent bigint, " +
                "foreign key(parent) references(id))");
        stat.execute("insert into test values(0, 0), (1, NULL), " +
                "(2, 1), (3, 3), (4, 3)");
        stat.execute("drop table test");

        stat.execute("create table parent(id int, x int)");
        stat.execute("insert into parent values(1, 2)");
        stat.execute("create table child(id int references parent(id)) as select 1");

        conn.close();
    }

    private void testWriteDelay() throws Exception {
        if (config.memory) {
            return;
        }
        Connection conn;
        Statement stat;
        ResultSet rs;
        deleteDb(getTestName());
        conn = getConnection(getTestName() + ";MV_STORE=TRUE");
        stat = conn.createStatement();
        stat.execute("create table test(id int)");
        stat.execute("set write_delay 0");
        stat.execute("insert into test values(1)");
        stat.execute("shutdown immediately");
        try {
            conn.close();
        } catch (Exception e) {
            // ignore
        }
        conn = getConnection(getTestName() + ";MV_STORE=TRUE");
        stat = conn.createStatement();
        rs = stat.executeQuery("select * from test");
        assertTrue(rs.next());
        conn.close();
    }

    private void testAutoCommit() throws SQLException {
        Connection conn;
        Statement stat;
        ResultSet rs;
        deleteDb(getTestName());
        conn = getConnection(getTestName() + ";MV_STORE=TRUE");
        for (int i = 0; i < 2; i++) {
            stat = conn.createStatement();
            stat.execute("create table test(id int primary key, name varchar)");
            stat.execute("create index on test(name)");
            conn.setAutoCommit(false);
            stat.execute("insert into test values(1, 'Hello')");
            stat.execute("insert into test values(2, 'World')");
            rs = stat.executeQuery("select count(*) from test");
            rs.next();
            assertEquals(2, rs.getInt(1));
            conn.rollback();
            rs = stat.executeQuery("select count(*) from test");
            rs.next();
            assertEquals(0, rs.getInt(1));

            stat.execute("insert into test values(1, 'Hello')");
            Savepoint sp = conn.setSavepoint();
            stat.execute("insert into test values(2, 'World')");
            conn.rollback(sp);
            rs = stat.executeQuery("select count(*) from test");
            rs.next();
            assertEquals(1, rs.getInt(1));
            stat.execute("drop table test");
        }

        conn.close();
    }

    private void testReopen() throws SQLException {
        if (config.memory) {
            return;
        }
        Connection conn;
        Statement stat;
        deleteDb(getTestName());
        conn = getConnection(getTestName() + ";MV_STORE=TRUE");
        stat = conn.createStatement();
        stat.execute("create table test(id int, name varchar)");
        conn.close();
        conn = getConnection(getTestName() + ";MV_STORE=TRUE");
        stat = conn.createStatement();
        stat.execute("drop table test");
        conn.close();
    }

    private void testBlob() throws SQLException, IOException {
        if (config.memory) {
            return;
        }
        deleteDb(getTestName());
        String dbName = getTestName() + ";MV_STORE=TRUE";
        Connection conn;
        Statement stat;
        conn = getConnection(dbName);
        stat = conn.createStatement();
        stat.execute("create table test(id int, name blob)");
        PreparedStatement prep = conn.prepareStatement(
                "insert into test values(1, ?)");
        prep.setBinaryStream(1,  new ByteArrayInputStream(new byte[129]));
        prep.execute();
        conn.close();
        conn = getConnection(dbName);
        stat = conn.createStatement();
        ResultSet rs = stat.executeQuery("select * from test");
        while (rs.next()) {
            InputStream in = rs.getBinaryStream(2);
            int len = 0;
            while (in.read() >= 0) {
                len++;
            }
            assertEquals(129, len);
        }
        conn.close();
    }

    private void testEncryption() throws Exception {
        if (config.memory) {
            return;
        }
        deleteDb(getTestName());
        String dbName = getTestName() + ";MV_STORE=TRUE";
        Connection conn;
        Statement stat;
        String url = getURL(dbName + ";CIPHER=AES", true);
        String user = "sa";
        String password = "123 123";
        conn = DriverManager.getConnection(url, user, password);
        stat = conn.createStatement();
        stat.execute("create table test(id int primary key)");
        conn.close();
        conn = DriverManager.getConnection(url, user, password);
        stat = conn.createStatement();
        stat.execute("select * from test");
        stat.execute("drop table test");
        conn.close();
    }

    private void testReadOnly() throws Exception {
        if (config.memory) {
            return;
        }
        deleteDb(getTestName());
        String dbName = getTestName() + ";MV_STORE=TRUE";
        Connection conn;
        Statement stat;
        conn = getConnection(dbName);
        stat = conn.createStatement();
        stat.execute("create table test(id int)");
        conn.close();
        FileUtils.setReadOnly(getBaseDir() + "/" + getTestName() +
                Constants.SUFFIX_MV_FILE);
        conn = getConnection(dbName);
        Database db = (Database) ((JdbcConnection) conn).getSession()
                .getDataHandler();
        assertTrue(db.getMvStore().getStore().getFileStore().isReadOnly());
        conn.close();
    }

    private void testReuseDiskSpace() throws Exception {
        deleteDb(getTestName());
        String dbName = getTestName() + ";MV_STORE=TRUE";
        Connection conn;
        Statement stat;
        long maxSize = 0;
        for (int i = 0; i < 20; i++) {
            conn = getConnection(dbName);
            Database db = (Database) ((JdbcConnection) conn).
                    getSession().getDataHandler();
            db.getMvStore().getStore().setRetentionTime(0);
            stat = conn.createStatement();
            stat.execute("create table test(id int primary key, data varchar)");
            stat.execute("insert into test select x, space(1000) " +
                    "from system_range(1, 1000)");
            stat.execute("drop table test");
            conn.close();
            long size = FileUtils.size(getBaseDir() + "/" + getTestName()
                    + Constants.SUFFIX_MV_FILE);
            if (i < 10) {
                maxSize = (int) (Math.max(size, maxSize) * 1.1);
            } else if (size > maxSize) {
                fail(i + " size: " + size + " max: " + maxSize);
            }
        }
    }

    private void testDataTypes() throws Exception {
        deleteDb(getTestName());
        String dbName = getTestName() + ";MV_STORE=TRUE";
        Connection conn = getConnection(dbName);
        Statement stat = conn.createStatement();

        stat.execute("create table test(id int primary key, " +
                "vc varchar," +
                "ch char(10)," +
                "bo boolean," +
                "by tinyint," +
                "sm smallint," +
                "bi bigint," +
                "de decimal," +
                "re real,"+
                "do double," +
                "ti time," +
                "da date," +
                "ts timestamp," +
                "bin binary," +
                "uu uuid," +
                "bl blob," +
                "cl clob)");
        stat.execute("insert into test values(1000, '', '', null, 0, 0, 0, "
                + "9, 2, 3, '10:00:00', '2001-01-01', "
                + "'2010-10-10 10:10:10', x'00', 0, x'b1', 'clob')");
        stat.execute("insert into test values(1, 'vc', 'ch', true, 8, 16, 64, "
                + "123.00, 64.0, 32.0, '10:00:00', '2001-01-01', "
                + "'2010-10-10 10:10:10', x'00', 0, x'b1', 'clob')");
        stat.execute("insert into test values(-1, "
                + "'quite a long string \u1234 \u00ff', 'ch', false, -8, -16, -64, "
                + "0, 0, 0, '10:00:00', '2001-01-01', "
                + "'2010-10-10 10:10:10', SECURE_RAND(100), 0, x'b1', 'clob')");
        stat.execute("insert into test values(-1000, space(1000), 'ch', "
                + "false, -8, -16, -64, "
                + "1, 1, 1, '10:00:00', '2001-01-01', "
                + "'2010-10-10 10:10:10', SECURE_RAND(100), 0, x'b1', 'clob')");
        if (!config.memory) {
            conn.close();
            conn = getConnection(dbName);
            stat = conn.createStatement();
        }
        ResultSet rs;
        rs = stat.executeQuery("select * from test order by id desc");
        rs.next();
        assertEquals(1000, rs.getInt(1));
        assertEquals("", rs.getString(2));
        assertEquals("", rs.getString(3));
        assertFalse(rs.getBoolean(4));
        assertEquals(0, rs.getByte(5));
        assertEquals(0, rs.getShort(6));
        assertEquals(0, rs.getLong(7));
        assertEquals("9", rs.getBigDecimal(8).toString());
        assertEquals(2d, rs.getDouble(9));
        assertEquals(3d, rs.getFloat(10));
        assertEquals("10:00:00", rs.getString(11));
        assertEquals("2001-01-01", rs.getString(12));
        assertEquals("2010-10-10 10:10:10", rs.getString(13));
        assertEquals(1, rs.getBytes(14).length);
        assertEquals("00000000-0000-0000-0000-000000000000",
                rs.getString(15));
        assertEquals(1, rs.getBytes(16).length);
        assertEquals("clob", rs.getString(17));
        rs.next();
        assertEquals(1, rs.getInt(1));
        assertEquals("vc", rs.getString(2));
        assertEquals("ch", rs.getString(3));
        assertTrue(rs.getBoolean(4));
        assertEquals(8, rs.getByte(5));
        assertEquals(16, rs.getShort(6));
        assertEquals(64, rs.getLong(7));
        assertEquals("123.00", rs.getBigDecimal(8).toString());
        assertEquals(64d, rs.getDouble(9));
        assertEquals(32d, rs.getFloat(10));
        assertEquals("10:00:00", rs.getString(11));
        assertEquals("2001-01-01", rs.getString(12));
        assertEquals("2010-10-10 10:10:10", rs.getString(13));
        assertEquals(1, rs.getBytes(14).length);
        assertEquals("00000000-0000-0000-0000-000000000000",
                rs.getString(15));
        assertEquals(1, rs.getBytes(16).length);
        assertEquals("clob", rs.getString(17));
        rs.next();
        assertEquals(-1, rs.getInt(1));
        assertEquals("quite a long string \u1234 \u00ff",
                rs.getString(2));
        assertEquals("ch", rs.getString(3));
        assertFalse(rs.getBoolean(4));
        assertEquals(-8, rs.getByte(5));
        assertEquals(-16, rs.getShort(6));
        assertEquals(-64, rs.getLong(7));
        assertEquals("0", rs.getBigDecimal(8).toString());
        assertEquals(0.0d, rs.getDouble(9));
        assertEquals(0.0d, rs.getFloat(10));
        assertEquals("10:00:00", rs.getString(11));
        assertEquals("2001-01-01", rs.getString(12));
        assertEquals("2010-10-10 10:10:10", rs.getString(13));
        assertEquals(100, rs.getBytes(14).length);
        assertEquals("00000000-0000-0000-0000-000000000000",
                rs.getString(15));
        assertEquals(1, rs.getBytes(16).length);
        assertEquals("clob", rs.getString(17));
        rs.next();
        assertEquals(-1000, rs.getInt(1));
        assertEquals(1000, rs.getString(2).length());
        assertEquals("ch", rs.getString(3));
        assertFalse(rs.getBoolean(4));
        assertEquals(-8, rs.getByte(5));
        assertEquals(-16, rs.getShort(6));
        assertEquals(-64, rs.getLong(7));
        assertEquals("1", rs.getBigDecimal(8).toString());
        assertEquals(1.0d, rs.getDouble(9));
        assertEquals(1.0d, rs.getFloat(10));
        assertEquals("10:00:00", rs.getString(11));
        assertEquals("2001-01-01", rs.getString(12));
        assertEquals("2010-10-10 10:10:10", rs.getString(13));
        assertEquals(100, rs.getBytes(14).length);
        assertEquals("00000000-0000-0000-0000-000000000000",
                rs.getString(15));
        assertEquals(1, rs.getBytes(16).length);
        assertEquals("clob", rs.getString(17));

        stat.execute("drop table test");

        stat.execute("create table test(id int, obj object, " +
                "rs result_set, arr array, ig varchar_ignorecase)");
        PreparedStatement prep = conn.prepareStatement(
                "insert into test values(?, ?, ?, ?, ?)");
        prep.setInt(1, 1);
        prep.setObject(2, new java.lang.AssertionError());
        prep.setObject(3, stat.executeQuery("select 1 from dual"));
        prep.setObject(4, new Object[]{1, 2});
        prep.setObject(5, "test");
        prep.execute();
        prep.setInt(1, 1);
        prep.setObject(2, new java.lang.AssertionError());
        prep.setObject(3, stat.executeQuery("select 1 from dual"));
        prep.setObject(4, new Object[]{
                new BigDecimal(new String(
                new char[1000]).replace((char) 0, '1'))});
        prep.setObject(5, "test");
        prep.execute();
        if (!config.memory) {
            conn.close();
            conn = getConnection(dbName);
            stat = conn.createStatement();
        }
        stat.execute("select * from test");

        rs = stat.executeQuery("script");
        int count = 0;
        while (rs.next()) {
            count++;
        }
        assertTrue(count < 10);

        stat.execute("drop table test");
        conn.close();
    }

    private void testSimple() throws Exception {
        deleteDb(getTestName());
        String dbName = getTestName() + ";MV_STORE=TRUE";
        Connection conn = getConnection(dbName);
        Statement stat = conn.createStatement();
        stat.execute("create table test(id int primary key, name varchar)");
        stat.execute("insert into test values(1, 'Hello'), (2, 'World')");
        ResultSet rs = stat.executeQuery("select *, _rowid_ from test");
        assertTrue(rs.next());
        assertEquals(1, rs.getInt(1));
        assertEquals("Hello", rs.getString(2));
        assertEquals(1, rs.getInt(3));

        stat.execute("update test set name = 'Hello' where id = 1");

        if (!config.memory) {
            conn.close();
            conn = getConnection(dbName);
            stat = conn.createStatement();
        }

        rs = stat.executeQuery("select * from test order by id");
        assertTrue(rs.next());
        assertEquals(1, rs.getInt(1));
        assertEquals("Hello", rs.getString(2));
        assertTrue(rs.next());
        assertEquals(2, rs.getInt(1));
        assertEquals("World", rs.getString(2));
        assertFalse(rs.next());

        stat.execute("create unique index idx_name on test(name)");
        rs = stat.executeQuery("select * from test " +
                "where name = 'Hello' order by name");
        assertTrue(rs.next());
        assertEquals(1, rs.getInt(1));
        assertEquals("Hello", rs.getString(2));
        assertFalse(rs.next());

        try {
            stat.execute("insert into test(id, name) values(10, 'Hello')");
            fail();
        } catch (SQLException e) {
            assertEquals(e.toString(), ErrorCode.DUPLICATE_KEY_1, e.getErrorCode());
        }

        rs = stat.executeQuery("select min(id), max(id), " +
                "min(name), max(name) from test");
        rs.next();
        assertEquals(1, rs.getInt(1));
        assertEquals(2, rs.getInt(2));
        assertEquals("Hello", rs.getString(3));
        assertEquals("World", rs.getString(4));
        assertFalse(rs.next());

        stat.execute("delete from test where id = 2");
        rs = stat.executeQuery("select * from test order by id");
        assertTrue(rs.next());
        assertEquals(1, rs.getInt(1));
        assertEquals("Hello", rs.getString(2));
        assertFalse(rs.next());

        stat.execute("alter table test add column firstName varchar");
        rs = stat.executeQuery("select * from test where name = 'Hello'");
        assertTrue(rs.next());
        assertEquals(1, rs.getInt(1));
        assertEquals("Hello", rs.getString(2));
        assertFalse(rs.next());

        if (!config.memory) {
            conn.close();
            conn = getConnection(dbName);
            stat = conn.createStatement();
        }

        rs = stat.executeQuery("select * from test order by id");
        assertTrue(rs.next());
        assertEquals(1, rs.getInt(1));
        assertEquals("Hello", rs.getString(2));
        assertFalse(rs.next());

        stat.execute("truncate table test");
        rs = stat.executeQuery("select * from test order by id");
        assertFalse(rs.next());

        rs = stat.executeQuery("select count(*) from test");
        rs.next();
        assertEquals(0, rs.getInt(1));
        stat.execute("insert into test(id) select x from system_range(1, 3000)");
        rs = stat.executeQuery("select count(*) from test");
        rs.next();
        assertEquals(3000, rs.getInt(1));
        try {
            stat.execute("insert into test(id) values(1)");
            fail();
        } catch (SQLException e) {
            assertEquals(ErrorCode.DUPLICATE_KEY_1, e.getErrorCode());
        }
        stat.execute("delete from test");
        stat.execute("insert into test(id, name) values(-1, 'Hello')");
        rs = stat.executeQuery("select count(*) from test where id = -1");
        rs.next();
        assertEquals(1, rs.getInt(1));
        rs = stat.executeQuery("select count(*) from test where name = 'Hello'");
        rs.next();
        assertEquals(1, rs.getInt(1));
        conn.close();
    }

    private void testReverseDeletePerformance() throws Exception {
        long direct = 0;
        long reverse = 0;
        for (int i = 0; i < 5; i++) {
            reverse += testReverseDeletePerformance(true);
            direct += testReverseDeletePerformance(false);
        }
        assertTrue("direct: " + direct + ", reverse: " + reverse, 2 * Math.abs(reverse - direct) < reverse + direct);
    }

    private long testReverseDeletePerformance(boolean reverse) throws Exception {
        deleteDb(getTestName());
        String dbName = getTestName() + ";MV_STORE=TRUE";
        try (Connection conn = getConnection(dbName)) {
            Statement stat = conn.createStatement();
            stat.execute("CREATE TABLE test(id INT PRIMARY KEY, name VARCHAR) AS " +
                    "SELECT x, x || space(1024) || x FROM system_range(1, 1000)");
            conn.setAutoCommit(false);
            PreparedStatement prep = conn.prepareStatement("DELETE FROM test WHERE id = ?");
            long start = System.nanoTime();
            for (int i = 0; i < 1000; i++) {
                prep.setInt(1, reverse ? 1000 - i : i);
                prep.execute();
            }
            long end = System.nanoTime();
            conn.commit();
            return TimeUnit.NANOSECONDS.toMillis(end - start);
        }
    }
}
