sqlitebrowser/src/sqlitedb.cpp

#include "sqlitedb.h"
#include "sqlitetablemodel.h"
#include "CipherDialog.h"

#include <QFile>
#include <QMessageBox>
#include <QProgressDialog>
#include <QApplication>
#include <QSettings>
#include <QDebug>
#include <QInputDialog>

// collation callbacks
int collCompare(void* /*pArg*/, int /*eTextRepA*/, const void* sA, int /*eTextRepB*/, const void* sB)
{
    size_t sizeA = strlen((const char*)sA);
    size_t sizeB = strlen((const char*)sB);

    if(sizeA == sizeB)
        return memcmp(sA, sB, sizeA);
    return sizeA - sizeB;
}

void collation_needed(void* /*pData*/, sqlite3* db, int eTextRep, const char* sCollationName)
{
    QMessageBox::StandardButton reply = QMessageBox::question(
                0,
                QObject::tr("Collation needed! Proceed?"),
                QObject::tr("A table in this database requires a special collation function '%1' "
                            "that this application can't provide without further knowledge.\n"
                            "If you choose to proceed, be aware bad things can happen to your database.\n"
                            "Create a backup!").arg(sCollationName), QMessageBox::Yes | QMessageBox::No);
    if(reply == QMessageBox::Yes)
        sqlite3_create_collation(db, sCollationName, eTextRep, NULL, collCompare);
}

bool DBBrowserDB::isOpen ( ) const
{
    return _db!=0;
}

bool DBBrowserDB::getDirty() const
{
    return !savepointList.empty();
}

bool DBBrowserDB::open(const QString& db)
{
    if (isOpen()) close();

    lastErrorMessage = tr("no error");

    isEncrypted = false;

    // Get encryption settings for database file
    CipherDialog* cipher = 0;
    if(tryEncryptionSettings(db, &isEncrypted, cipher) == false)
    {
        lastErrorMessage = QString::fromUtf8((const char*)sqlite3_errmsg(_db));
        return false;
    }

    // Open database file
    if(sqlite3_open_v2(db.toUtf8(), &_db, SQLITE_OPEN_READWRITE, NULL) != SQLITE_OK)
    {
        lastErrorMessage = QString::fromUtf8((const char*)sqlite3_errmsg(_db));
        return false;
    }

    // Set encryption details if database is encrypted
#ifdef ENABLE_SQLCIPHER
    if(isEncrypted && cipher)
    {
        sqlite3_key(_db, cipher->password().toUtf8(), cipher->password().toUtf8().length());
        if(cipher->pageSize() != 1024)
            sqlite3_exec(_db, QString("PRAGMA cipher_page_size = %1;").arg(cipher->pageSize()).toUtf8(), NULL, NULL, NULL);
    }
#endif
    delete cipher;

    if (_db)
    {
        // register collation callback
        sqlite3_collation_needed(_db, NULL, collation_needed);

        // set preference defaults
        QSettings settings(QApplication::organizationName(), QApplication::organizationName());
        settings.sync();
        bool foreignkeys = settings.value( "/db/foreignkeys", false ).toBool();
        setPragma("foreign_keys", foreignkeys ? "1" : "0");

        // Enable extension loading
        sqlite3_enable_load_extension(_db, 1);

        curDBFilename = db;
        return true;
    } else {
        return false;
    }
}

bool DBBrowserDB::attach(const QString& filename, QString attach_as)
{
    // Ask for name to be given to the attached database if none was provided
    if(attach_as.isEmpty())
        attach_as = QInputDialog::getText(0,
                                          qApp->applicationName(),
                                          tr("Please specify the database name under which you want to access the attached database")
                                          ).trimmed();
    if(attach_as.isEmpty())
        return false;

#ifdef ENABLE_SQLCIPHER
    // Try encryption settings
    CipherDialog* cipher = 0;
    bool is_encrypted;
    if(tryEncryptionSettings(filename, &is_encrypted, cipher) == false)
        return false;

    // Attach database
    QString key;
    if(cipher) key = cipher->password();
    if(!executeSQL(QString("ATTACH '%1' AS `%2` KEY '%3'").arg(filename).arg(attach_as).arg(key), false))
    {
        QMessageBox::warning(0, qApp->applicationName(), lastErrorMessage);
        return false;
    }
    if(cipher && cipher->pageSize() != 1024)
    {
        if(!executeSQL(QString("PRAGMA `%1`.cipher_page_size = %2").arg(attach_as).arg(cipher->pageSize()), false))
        {
            QMessageBox::warning(0, qApp->applicationName(), lastErrorMessage);
            return false;
        }
    }
#else
    // Attach database
    if(!executeSQL(QString("ATTACH '%1' AS `%2`").arg(filename).arg(attach_as), false))
    {
        QMessageBox::warning(0, qApp->applicationName(), lastErrorMessage);
        return false;
    }
#endif

    return true;
}

bool DBBrowserDB::tryEncryptionSettings(const QString& filename, bool* encrypted, CipherDialog*& cipherSettings)
{
    // Open database file
    sqlite3* dbHandle;
    if(sqlite3_open_v2(filename.toUtf8(), &dbHandle, SQLITE_OPEN_READWRITE, NULL) != SQLITE_OK)
        return false;

    // Try reading from database
    *encrypted = false;
    cipherSettings = 0;
    while(true)
    {
        QString statement = "SELECT COUNT(*) FROM sqlite_master;";
        QByteArray utf8Statement = statement.toUtf8();
        sqlite3_stmt* vm;
        const char* tail;
        sqlite3_prepare_v2(dbHandle, utf8Statement, utf8Statement.length(), &vm, &tail);
        if(sqlite3_step(vm) != SQLITE_ROW)
        {
            sqlite3_finalize(vm);
#ifdef ENABLE_SQLCIPHER
            delete cipherSettings;
            cipherSettings = new CipherDialog(0, false);
            if(cipherSettings->exec())
            {
                // Close and reopen database first to be in a clean state after the failed read attempt from above
                sqlite3_close(dbHandle);
                if(sqlite3_open_v2(filename.toUtf8(), &dbHandle, SQLITE_OPEN_READWRITE, NULL) != SQLITE_OK)
                {
                    delete cipherSettings;
                    cipherSettings = 0;
                    return false;
                }

                // Set key and, if it differs from the default value, the page size
                sqlite3_key(dbHandle, cipherSettings->password().toUtf8(), cipherSettings->password().toUtf8().length());
                if(cipherSettings->pageSize() != 1024)
                    sqlite3_exec(dbHandle, QString("PRAGMA cipher_page_size = %1;").arg(cipherSettings->pageSize()).toUtf8(), NULL, NULL, NULL);

                *encrypted = true;
            } else {
                sqlite3_close(dbHandle);
                *encrypted = false;
                delete cipherSettings;
                cipherSettings = 0;
                return false;
            }
#else
            sqlite3_close(dbHandle);
            return false;
#endif
        } else {
            sqlite3_finalize(vm);
            sqlite3_close(dbHandle);
            return true;
        }
    }
}

bool DBBrowserDB::setRestorePoint(const QString& pointname)
{
    if(!isOpen())
        return false;
    if(savepointList.contains(pointname))
        return true;

    if(_db)
    {
        QString query = QString("SAVEPOINT %1;").arg(pointname);
        sqlite3_exec(_db, query.toUtf8(), NULL, NULL, NULL);
        savepointList.append(pointname);
        emit dbChanged(getDirty());
    }
    return true;
}

bool DBBrowserDB::save(const QString& pointname)
{
    if(!isOpen() || savepointList.contains(pointname) == false)
        return false;

    if(_db)
    {
        QString query = QString("RELEASE %1;").arg(pointname);
        sqlite3_exec(_db, query.toUtf8(), NULL,NULL,NULL);
        savepointList.removeAll(pointname);
        emit dbChanged(getDirty());
    }
    return true;
}

bool DBBrowserDB::revert(const QString& pointname)
{
    if(!isOpen() || savepointList.contains(pointname) == false)
        return false;

    if(_db)
    {
        QString query = QString("ROLLBACK TO SAVEPOINT %1;").arg(pointname);
        sqlite3_exec(_db, query.toUtf8(), NULL, NULL, NULL);
        query = QString("RELEASE %1;").arg(pointname);
        sqlite3_exec(_db, query.toUtf8(), NULL, NULL, NULL);
        savepointList.removeAll(pointname);
        emit dbChanged(getDirty());
    }
    return true;
}

bool DBBrowserDB::saveAll()
{
    foreach(const QString& point, savepointList)
    {
        if(!save(point))
            return false;
    }
    return true;
}

bool DBBrowserDB::revertAll()
{
    foreach(const QString& point, savepointList)
    {
        if(!revert(point))
            return false;
    }
    return true;
}

bool DBBrowserDB::create ( const QString & db)
{
    bool ok=false;

    if (isOpen()) close();

    lastErrorMessage = tr("no error");

    // read encoding from settings and open with sqlite3_open for utf8
    // and sqlite3_open16 for utf16
    QSettings settings(QApplication::organizationName(), QApplication::organizationName());
    QString sEncoding = settings.value("/db/defaultencoding", "UTF-8").toString();

    int openresult = SQLITE_OK;

    if(sEncoding == "UTF-8" || sEncoding == "UTF8" || sEncoding == "Latin1")
        openresult = sqlite3_open(db.toUtf8(), &_db);
    else
        openresult = sqlite3_open16(db.utf16(), &_db);

    if( openresult != SQLITE_OK ){
        lastErrorMessage = QString::fromUtf8((const char*)sqlite3_errmsg(_db));
        sqlite3_close(_db);
        _db = 0;
        return false;
    }

    if (_db)
    {
        // Enable extension loading
        sqlite3_enable_load_extension(_db, 1);

        // force sqlite3 do write proper file header
        // if we don't create and drop the table we might end up
        // with a 0 byte file, if the user cancels the create table dialog
        sqlite3_exec(_db, "CREATE TABLE notempty (id integer primary key);", NULL, NULL, NULL);
        sqlite3_exec(_db, "DROP TABLE notempty", NULL, NULL, NULL);
        sqlite3_exec(_db, "COMMIT;", NULL, NULL, NULL);

        ok = true;
        curDBFilename = db;
    }

    return ok;
}


bool DBBrowserDB::close()
{
    if(_db)
    {
        if (getDirty())
        {
            QMessageBox::StandardButton reply = QMessageBox::question(0,
                                                                      QApplication::applicationName(),
                                                                      tr("Do you want to save the changes "
                                                                         "made to the database file %1?").arg(curDBFilename),
                                                                      QMessageBox::Yes | QMessageBox::No | QMessageBox::Cancel);

            // If the user clicked the cancel button stop here and return false
            if(reply == QMessageBox::Cancel)
                return false;

            // If he didn't it was either yes or no
            if(reply == QMessageBox::Yes)
                saveAll();
            else
                revertAll(); //not really necessary, I think... but will not hurt.
        }
        sqlite3_close(_db);
    }
    _db = 0;
    objMap.clear();
    savepointList.clear();
    emit dbChanged(getDirty());

    // Return true to tell the calling function that the closing wasn't cancelled by the user
    return true;
}

bool DBBrowserDB::dump(const QString& filename)
{
    // Open file
    QFile file(filename);
    if(file.open(QIODevice::WriteOnly))
    {
        QApplication::setOverrideCursor(Qt::WaitCursor);

        size_t numRecordsTotal = 0, numRecordsCurrent = 0;
        QList<DBBrowserObject> tables = objMap.values("table");
        QMutableListIterator<DBBrowserObject> it(tables);
        while(it.hasNext())
        {
            it.next();

            // Remove the sqlite_stat1 table if there is one
            if(it.value().getname() == "sqlite_stat1" || it.value().getname() == "sqlite_sequence")
            {
                it.remove();
            } else {
                // Otherwise get the number of records in this table
                SqliteTableModel tableModel(0, this);
                tableModel.setTable(it.value().getname());
                numRecordsTotal += tableModel.totalRowCount();
            }
        }

        QProgressDialog progress(tr("Exporting database to SQL file..."),
                                 tr("Cancel"), 0, numRecordsTotal);
        progress.setWindowModality(Qt::ApplicationModal);
        progress.show();
        qApp->processEvents();

        // Open text stream to the file
        QTextStream stream(&file);

        // Put the SQL commands in a transaction block
        stream << "BEGIN TRANSACTION;\n";

        // Loop through all tables first as they are required to generate views, indices etc. later
        for(QList<DBBrowserObject>::ConstIterator it=tables.begin();it!=tables.end();++it)
        {
            // Write the SQL string used to create this table to the output file
            stream << it->getsql() << ";\n";

            QString sQuery = QString("SELECT * FROM `%1`;").arg(it->getTableName());
            QByteArray utf8Query = sQuery.toUtf8();
            sqlite3_stmt *stmt;

            int status = sqlite3_prepare_v2(this->_db, utf8Query.data(), utf8Query.size(), &stmt, NULL);
            if(SQLITE_OK == status)
            {
                int columns = sqlite3_column_count(stmt);
                size_t counter = 0;
                qApp->processEvents();
                while(sqlite3_step(stmt) == SQLITE_ROW)
                {
                    stream << "INSERT INTO `" << it->getTableName() << "` VALUES (";
                    for (int i = 0; i < columns; ++i)
                    {
                        int fieldsize = sqlite3_column_bytes(stmt, i);
                        int fieldtype = sqlite3_column_type(stmt, i);
                        QByteArray bcontent(
                                    (const char*)sqlite3_column_blob(stmt, i),
                                    fieldsize);

                        if(bcontent.left(2048).contains('\0')) // binary check
                        {
                            stream << QString("X'%1'").arg(QString(bcontent.toHex()));
                        }
                        else
                        {
                            switch(fieldtype)
                            {
                            case SQLITE_TEXT:
                            case SQLITE_BLOB:
                                stream << "'" << bcontent.replace("'", "''") << "'";
                            break;
                            case SQLITE_NULL:
                                stream << "NULL";
                            break;
                            default:
                                stream << bcontent;
                            }
                        }
                        if(i != columns - 1)
                            stream << ',';
                    }
                    stream << ");\n";

                    progress.setValue(++numRecordsCurrent);
                    if(counter % 5000 == 0)
                        qApp->processEvents();
                    counter++;

                    if(progress.wasCanceled())
                    {
                        sqlite3_finalize(stmt);
                        file.close();
                        file.remove();
                        QApplication::restoreOverrideCursor();
                        return false;
                    }
                }
            }
            sqlite3_finalize(stmt);
        }

        // Now dump all the other objects
        for(objectMap::ConstIterator it=objMap.begin();it!=objMap.end();++it)
        {
            // Make sure it's not a table again
            if(it.value().gettype() == "table")
                continue;

            // Write the SQL string used to create this object to the output file
            if(!it->getsql().isEmpty())
            {
                stream << it->getsql() << ";\n";
            }
        }

        // Done
        stream << "COMMIT;\n";
        file.close();

        QApplication::restoreOverrideCursor();
        qApp->processEvents();
        return true;
    }
    return false;
}

bool DBBrowserDB::executeSQL ( const QString & statement, bool dirtyDB, bool logsql)
{
    char *errmsg;
    bool ok = false;

    if (!isOpen()) return false;

    if (_db){
        if (logsql) logSQL(statement, kLogMsg_App);
        if (dirtyDB) setRestorePoint();
        if (SQLITE_OK==sqlite3_exec(_db,statement.toUtf8(),
                                    NULL,NULL,&errmsg)){
            ok=true;
        }
    }

    if (!ok){
        lastErrorMessage = QString::fromUtf8(errmsg);
        qWarning() << "executeSQL: " << statement << "->" << lastErrorMessage;
        return false;
    }
    return true;
}

bool DBBrowserDB::executeMultiSQL(const QString& statement, bool dirty, bool log)
{
    // First check if a DB is opened
    if(!isOpen())
        return false;

    // Log the statement if needed
    if(log)
        logSQL(statement, kLogMsg_App);

    // Set DB to dirty/create restore point if necessary
    if(dirty)
        setRestorePoint();

    // Show progress dialog
    int statement_size = statement.size();
    QProgressDialog progress(tr("Executing SQL..."),
                             tr("Cancel"), 0, statement_size);
    progress.setWindowModality(Qt::ApplicationModal);
    progress.show();

    // Execute the statement by looping until SQLite stops giving back a tail string
    sqlite3_stmt* vm;
    QByteArray utf8Query = statement.toUtf8();
    const char *tail = utf8Query.data();
    int res = 0;
    unsigned int line = 0;
    do
    {
        line++;
        size_t tail_length = strlen(tail);

        // Update progress dialog, keep UI responsive
        progress.setValue(statement_size - tail_length);
        qApp->processEvents();
        if(progress.wasCanceled())
        {
            lastErrorMessage = tr("Action cancelled.");
            return false;
        }

        // Execute next statement
        res = sqlite3_prepare_v2(_db, tail, tail_length, &vm, &tail);
        if(res == SQLITE_OK)
        {
            if(sqlite3_step(vm) == SQLITE_ERROR)
            {
                sqlite3_finalize(vm);
                lastErrorMessage = tr("Error in statement #%1: %2.\n"
                    "Aborting execution.").arg(line).arg(sqlite3_errmsg(_db));
                qWarning() << lastErrorMessage;
                return false;
            } else {
                sqlite3_finalize(vm);
            }
        } else {
            lastErrorMessage = tr("Error in statement #%1: %2.\n"
                "Aborting execution.").arg(line).arg(sqlite3_errmsg(_db));
            qWarning() << lastErrorMessage;
            return false;
        }
    } while(tail && *tail != 0 && (res == SQLITE_OK || res == SQLITE_DONE));

    // Exit
    return true;
}

bool DBBrowserDB::getRow(const QString& sTableName, sqlite3_int64 rowid, QList<QByteArray>& rowdata)
{
    QString sQuery = QString("SELECT * FROM `%1` WHERE `%2`=%3;").arg(sTableName).arg(getObjectByName(sTableName).table.rowidColumn()).arg(rowid);
    QByteArray utf8Query = sQuery.toUtf8();
    sqlite3_stmt *stmt;
    bool ret = false;

    int status = sqlite3_prepare_v2(_db, utf8Query, utf8Query.size(), &stmt, NULL);
    if(SQLITE_OK == status)
    {
        // even this is a while loop, the statement should always only return 1 row
        while(sqlite3_step(stmt) == SQLITE_ROW)
        {
            for (int i = 0; i < sqlite3_column_count(stmt); ++i)
                rowdata.append(QByteArray(static_cast<const char*>(sqlite3_column_blob(stmt, i)), sqlite3_column_bytes(stmt, i)));
            ret = true;
        }
    }
    sqlite3_finalize(stmt);

    return ret;
}

int64_t DBBrowserDB::max(const sqlb::Table& t, sqlb::FieldPtr field) const
{
    QString sQuery = QString("SELECT MAX(`%2`) from `%1`;").arg(t.name()).arg(field->name());
    QByteArray utf8Query = sQuery.toUtf8();
    sqlite3_stmt *stmt;
    int64_t ret = 0;

    int status = sqlite3_prepare_v2(_db, utf8Query, utf8Query.size(), &stmt, NULL);
    if(SQLITE_OK == status)
    {
        // even this is a while loop, the statement should always only return 1 row
        while(sqlite3_step(stmt) == SQLITE_ROW)
        {
            if(sqlite3_column_count(stmt) == 1)
            {
                ret = sqlite3_column_int64(stmt, 0);
            }
        }
    }
    sqlite3_finalize(stmt);

    return ret;
}

QString DBBrowserDB::emptyInsertStmt(const sqlb::Table& t, sqlite3_int64 pk_value) const
{
    QString stmt = QString("INSERT INTO `%1`").arg(t.name());

    QStringList vals;
    QStringList fields;
    foreach(sqlb::FieldPtr f, t.fields()) {
        if(f->primaryKey()) {
            if(f->isInteger())
            {
                fields << f->name();

                if(pk_value != -1)
                    vals << QString::number(pk_value);
                else
                {
                    if(f->notnull())
                    {
                        int64_t maxval = this->max(t, f);
                        vals << QString::number(maxval + 1);
                    }
                    else
                    {
                        vals << "NULL";
                    }
                }
            }
            else
            {
                fields << f->name();

                vals << "''";
            }
        } else if(f->notnull() && f->defaultValue().length() == 0) {
            fields << f->name();

            if(f->isInteger())
                vals << "0";
            else
                vals << "''";
        } else {
            // don't insert into fields with a default value
            // or we will never see it.
            if(f->defaultValue().length() == 0)
            {
                fields << f->name();
                vals << "NULL";
            }
        }
    }

    if(!fields.empty())
    {
        stmt.append("(`");
        stmt.append(fields.join("`,`"));
        stmt.append("`)");
    }
    stmt.append(" VALUES (");
    stmt.append(vals.join(","));
    stmt.append(");");

    return stmt;
}

long DBBrowserDB::addRecord(const QString& sTableName)
{
    char *errmsg;
    if (!isOpen()) return false;

    sqlb::Table table = getObjectByName(sTableName).table;

    // For tables without rowid we have to set the primary key by ourselves. We do so by querying for the largest value in the PK column
    // and adding one to it.
    QString sInsertstmt;
    long pk_value;
    if(table.isWithoutRowidTable())
    {
        SqliteTableModel m(this, this);
        m.setQuery(QString("SELECT MAX(`%1`) FROM `%2`;").arg(table.rowidColumn()).arg(sTableName));
        pk_value = m.data(m.index(0, 0)).toLongLong() + 1;
        sInsertstmt = emptyInsertStmt(table, pk_value);
    } else {
        sInsertstmt = emptyInsertStmt(table);
    }

    lastErrorMessage = "";
    logSQL(sInsertstmt, kLogMsg_App);
    setRestorePoint();

    if (SQLITE_OK != sqlite3_exec(_db, sInsertstmt.toUtf8(), NULL, NULL, &errmsg))
    {
        lastErrorMessage = QString::fromUtf8(errmsg);
        qWarning() << "addRecord: " << lastErrorMessage;
        return -1;
    } else {
        if(table.isWithoutRowidTable())
            return pk_value;
        else
            return sqlite3_last_insert_rowid(_db);
    }
}

bool DBBrowserDB::deleteRecord(const QString& table, sqlite3_int64 rowid)
{
    char * errmsg;
    if (!isOpen()) return false;
    bool ok = false;
    lastErrorMessage = QString("no error");

    QString statement = QString("DELETE FROM `%1` WHERE `%2`=%3;").arg(table).arg(getObjectByName(table).table.rowidColumn()).arg(rowid);

    if (_db){
        logSQL(statement, kLogMsg_App);
        setRestorePoint();
        if (SQLITE_OK==sqlite3_exec(_db,statement.toUtf8(),
                                    NULL,NULL,&errmsg)){
            ok=true;
        } else {
            lastErrorMessage = QString::fromUtf8(errmsg);
            qWarning() << "deleteRecord: " << lastErrorMessage;
        }
    }
    return ok;
}

bool DBBrowserDB::updateRecord(const QString& table, const QString& column, sqlite3_int64 row, const QByteArray& value)
{
    if (!isOpen()) return false;

    lastErrorMessage = QString("no error");

    QString sql = QString("UPDATE `%1` SET `%2`=? WHERE `%3`=%4;").arg(table).arg(column).arg(getObjectByName(table).table.rowidColumn()).arg(row);

    logSQL(sql, kLogMsg_App);
    setRestorePoint();

    sqlite3_stmt* stmt;
    int success = 1;
    if(sqlite3_prepare_v2(_db, sql.toUtf8(), -1, &stmt, 0) != SQLITE_OK)
        success = 0;
    if(success == 1 && sqlite3_bind_text(stmt, 1, value.constData(), value.length(), SQLITE_STATIC) != SQLITE_OK)
        success = -1;
    if(success == 1 && sqlite3_step(stmt) != SQLITE_DONE)
        success = -1;
    if(success != 0 && sqlite3_finalize(stmt) != SQLITE_OK)
        success = -1;

    if(success == 1)
    {
        return true;
    } else {
        lastErrorMessage = sqlite3_errmsg(_db);
        qWarning() << "updateRecord: " << lastErrorMessage;
        return false;
    }
}

bool DBBrowserDB::createTable(const QString& name, const sqlb::FieldVector& structure)
{
    // Build SQL statement
    sqlb::Table table(name);
    for(int i=0;i<structure.size();i++)
        table.addField(structure.at(i));

    // Execute it and update the schema
    bool result = executeSQL(table.sql());
    updateSchema();
    return result;
}

bool DBBrowserDB::addColumn(const QString& tablename, const sqlb::FieldPtr& field)
{
    QString sql = QString("ALTER TABLE `%1` ADD COLUMN %2").arg(tablename).arg(field->toString());

    // Execute it and update the schema
    bool result = executeSQL(sql);
    updateSchema();
    return result;
}

bool DBBrowserDB::renameColumn(const QString& tablename, const QString& name, sqlb::FieldPtr to, int move)
{
    // NOTE: This function is working around the incomplete ALTER TABLE command in SQLite.
    // If SQLite should fully support this command one day, this entire
    // function can be changed to executing something like this:
    //QString sql;
    //if(to.isNull())
    //    sql = QString("ALTER TABLE `%1` DROP COLUMN `%2`;").arg(table).arg(column);
    //else
    //    sql = QString("ALTER TABLE `%1` MODIFY `%2` %3").arg(tablename).arg(to).arg(type);    // This is wrong...
    //return executeSQL(sql);

    // Collect information on the current DB layout
    QString tableSql = getObjectByName(tablename).getsql();
    if(tableSql.isEmpty())
    {
        lastErrorMessage = tr("renameColumn: cannot find table %1.").arg(tablename);
        qWarning() << lastErrorMessage;
        return false;
    }

    // Create table schema
    sqlb::Table oldSchema = sqlb::Table::parseSQL(tableSql).first;

    // Check if field actually exists
    if(oldSchema.findField(name) == -1)
    {
        lastErrorMessage = tr("renameColumn: cannot find column %1.").arg(name);
        qWarning() << lastErrorMessage;
        return false;
    }

    // Create savepoint to be able to go back to it in case of any error
    if(!executeSQL("SAVEPOINT sqlitebrowser_rename_column"))
    {
        lastErrorMessage = tr("renameColumn: creating savepoint failed. DB says: %1").arg(lastErrorMessage);
        qWarning() << lastErrorMessage;
        return false;
    }

    // Create a new table with a name that hopefully doesn't exist yet.
    // Its layout is exactly the same as the one of the table to change - except for the column to change
    // of course
    sqlb::Table newSchema = oldSchema;
    newSchema.setName("sqlitebrowser_rename_column_new_table");
    QString select_cols;
    if(to.isNull())
    {
        // We want drop the column - so just remove the field
        newSchema.removeField(name);

        for(int i=0;i<newSchema.fields().count();++i)
            select_cols.append(QString("`%1`,").arg(newSchema.fields().at(i)->name()));
        select_cols.chop(1);    // remove last comma
    } else {
        // We want to modify it

        // Move field
        int index = newSchema.findField(name);
        sqlb::FieldPtr temp = newSchema.fields().at(index);
        newSchema.setField(index, newSchema.fields().at(index + move));
        newSchema.setField(index + move, temp);

        // Get names of fields to select from old table now - after the field has been moved and before it might be renamed
        for(int i=0;i<newSchema.fields().count();++i)
            select_cols.append(QString("`%1`,").arg(newSchema.fields().at(i)->name()));
        select_cols.chop(1);    // remove last comma

        // Modify field
        newSchema.setField(index + move, to);
    }

    // Create the new table
    if(!executeSQL(newSchema.sql()))
    {
        lastErrorMessage = tr("renameColumn: creating new table failed. DB says: %1").arg(lastErrorMessage);
        qWarning() << lastErrorMessage;
        executeSQL("ROLLBACK TO SAVEPOINT sqlitebrowser_rename_column;");
        return false;
    }

    // Copy the data from the old table to the new one
    if(!executeSQL(QString("INSERT INTO sqlitebrowser_rename_column_new_table SELECT %1 FROM `%2`;").arg(select_cols).arg(tablename)))
    {
        lastErrorMessage = tr("renameColumn: copying data to new table failed. DB says:\n%1").arg(lastErrorMessage);
        qWarning() << lastErrorMessage;
        executeSQL("ROLLBACK TO SAVEPOINT sqlitebrowser_rename_column;");
        return false;
    }

    // Save all indices, triggers and views associated with this table because SQLite deletes them when we drop the table in the next step
    QString otherObjectsSql;
    for(objectMap::ConstIterator it=objMap.begin();it!=objMap.end();++it)
    {
        // If this object references the table and it's not the table itself save it's SQL string
        if((*it).getTableName() == tablename && (*it).gettype() != "table")
            otherObjectsSql += (*it).getsql() + "\n";
    }

    // Delete the old table
    if(!executeSQL(QString("DROP TABLE `%1`;").arg(tablename)))
    {
        lastErrorMessage = tr("renameColumn: deleting old table failed. DB says: %1").arg(lastErrorMessage);
        qWarning() << lastErrorMessage;
        executeSQL("ROLLBACK TO SAVEPOINT sqlitebrowser_rename_column;");
        return false;
    }

    // Rename the temporary table
    if(!renameTable("sqlitebrowser_rename_column_new_table", tablename))
    {
        executeSQL("ROLLBACK TO SAVEPOINT sqlitebrowser_rename_column;");
        return false;
    }

    // Restore the saved triggers, views and indices
    if(!executeMultiSQL(otherObjectsSql, true, true))
    {
        QMessageBox::information(0, qApp->applicationName(), tr("Restoring some of the objects associated with this table failed. "
                                                                "This is most likely because some column names changed. "
                                                                "Here's the SQL statement which you might want to fix and execute manually:\n\n")
                                 + otherObjectsSql);
    }

    // Release the savepoint - everything went fine
    if(!executeSQL("RELEASE SAVEPOINT sqlitebrowser_rename_column;"))
    {
        lastErrorMessage = tr("renameColumn: releasing savepoint failed. DB says: %1").arg(lastErrorMessage);
        qWarning() << lastErrorMessage;
        return false;
    }

    // Success, update the DB schema before returning
    updateSchema();
    return true;
}

bool DBBrowserDB::renameTable(const QString& from_table, const QString& to_table)
{
    QString sql = QString("ALTER TABLE `%1` RENAME TO `%2`").arg(from_table, to_table);
    if(!executeSQL(sql))
    {
        QString error = tr("Error renaming table '%1' to '%2'."
            "Message from database engine:\n%3").arg(from_table).arg(to_table).arg(lastErrorMessage);
        lastErrorMessage = error;
        qWarning() << lastErrorMessage;
        return false;
    } else {
        updateSchema();
        return true;
    }
}

QStringList DBBrowserDB::getBrowsableObjectNames() const
{
    objectMap::ConstIterator it;
    QStringList res;

    for(it=objMap.begin();it!=objMap.end();++it)
    {
        if(it.key() == "table" || it.key() == "view")
            res.append(it.value().getname());
    }

    return res;
}

objectMap DBBrowserDB::getBrowsableObjects() const
{
    objectMap::ConstIterator it;
    objectMap res;

    for(it=objMap.begin();it!=objMap.end();++it)
    {
        if(it.key() == "table" || it.key() == "view")
            res.insert(it.key(), it.value());
    }

    return res;
}

DBBrowserObject DBBrowserDB::getObjectByName(const QString& name) const
{
    for (objectMap::ConstIterator it = objMap.begin(); it != objMap.end(); ++it )
    {
        if((*it).getname() == name)
            return *it;
    }
    return DBBrowserObject();
}

void DBBrowserDB::logSQL(QString statement, int msgtype)
{
    // Replace binary log messages by a placeholder text instead of printing gibberish
    for(int i=0;i<statement.size();i++)
    {
        if(statement.at(i) < 32 && statement.at(i) != '\n')
        {
            statement.truncate(32);
            statement.append(tr("... <string can not be logged, contains binary data> ..."));

            // early exit if we detect a binary character,
            // to prevent checking all characters in a potential big string
            break;
        }
    }

    emit sqlExecuted(statement, msgtype);
}

void DBBrowserDB::updateSchema( )
{
    sqlite3_stmt *vm;
    const char *tail;
    int err=0;
    lastErrorMessage = tr("no error");

    objMap.clear();

    // Exit here is no DB is opened
    if(!isOpen())
        return;

    QString statement = "SELECT type,name,sql,tbl_name FROM sqlite_master UNION SELECT type,name,sql,tbl_name FROM sqlite_temp_master;";

    QByteArray utf8Statement = statement.toUtf8();
    err=sqlite3_prepare_v2(_db, utf8Statement, utf8Statement.length(),
                        &vm, &tail);
    if (err == SQLITE_OK){
        logSQL(statement, kLogMsg_App);
        while ( sqlite3_step(vm) == SQLITE_ROW ){
            QString val1 = QString::fromUtf8((const char*)sqlite3_column_text(vm, 0));
            QString val2 = QString::fromUtf8((const char*)sqlite3_column_text(vm, 1));
            QString val3 = QString::fromUtf8((const char*)sqlite3_column_text(vm, 2));
            QString val4 = QString::fromUtf8((const char*)sqlite3_column_text(vm, 3));
            val3.replace("\r", "");

            if(val1 == "table" || val1 == "index" || val1 == "view" || val1 == "trigger")
                objMap.insert(val1, DBBrowserObject(val2, val3, val1, val4));
            else
                qWarning() << tr("unknown object type %1").arg(val1);
        }
        sqlite3_finalize(vm);
    }else{
        qWarning() << tr("could not get list of db objects: %1, %2").arg(err).arg(sqlite3_errmsg(_db));
    }

    //now get the field list for each table
    objectMap::Iterator it;
    for ( it = objMap.begin(); it != objMap.end(); ++it )
    {
        // Use our SQL parser to generate the field list for tables. For views we currently have to fall back to the
        // pragma SQLite offers.
        if((*it).gettype() == "table")
        {
            (*it).table = sqlb::Table::parseSQL((*it).getsql()).first;
        } else if((*it).gettype() == "view") {
            statement = QString("PRAGMA TABLE_INFO(`%1`);").arg((*it).getname());
            logSQL(statement, kLogMsg_App);
            err=sqlite3_prepare_v2(_db,statement.toUtf8(),statement.length(),
                                &vm, &tail);
            if (err == SQLITE_OK){
                while ( sqlite3_step(vm) == SQLITE_ROW ){
                    if (sqlite3_column_count(vm)==6)
                    {
                        QString val_name = QString::fromUtf8((const char *)sqlite3_column_text(vm, 1));
                        QString val_type = QString::fromUtf8((const char *)sqlite3_column_text(vm, 2));

                        sqlb::FieldPtr f(new sqlb::Field(val_name, val_type));
                        (*it).table.addField(f);
                    }
                }
                sqlite3_finalize(vm);
            } else{
                lastErrorMessage = tr("could not get types");
            }
        }
    }
}

QString DBBrowserDB::getPragma(const QString& pragma)
{
    if(!isOpen())
        return "";

    QString sql = QString("PRAGMA %1").arg(pragma);
    sqlite3_stmt* vm;
    const char* tail;
    QString retval = "";

    // Get value from DB
    int err = sqlite3_prepare_v2(_db, sql.toUtf8(), sql.toUtf8().length(), &vm, &tail);
    if(err == SQLITE_OK){
        logSQL(sql, kLogMsg_App);
        if(sqlite3_step(vm) == SQLITE_ROW)
            retval = QString::fromUtf8((const char *) sqlite3_column_text(vm, 0));
        else
            qWarning() << tr("didn't receive any output from pragma %1").arg(pragma);

        sqlite3_finalize(vm);
    } else {
        qWarning() << tr("could not execute pragma command: %1, %2").arg(err).arg(sqlite3_errmsg(_db));
    }

    // Return it
    return retval;
}

bool DBBrowserDB::setPragma(const QString& pragma, const QString& value)
{
    // Set the pragma value
    QString sql = QString("PRAGMA %1 = \"%2\";").arg(pragma).arg(value);

    save();
    bool res = executeSQL(sql, false, true); // PRAGMA statements are usually not transaction bound, so we can't revert
    if( !res )
        qWarning() << tr("Error setting pragma %1 to %2: %3").arg(pragma).arg(value).arg(lastErrorMessage);
    return res;
}

bool DBBrowserDB::setPragma(const QString& pragma, const QString& value, QString& originalvalue)
{
    if( originalvalue != value )
    {
        if( setPragma(pragma, value))
        {
            originalvalue = value;
            return true;
        }
    }
    return false;
}

bool DBBrowserDB::setPragma(const QString& pragma, int value, int& originalvalue)
{
    if( originalvalue != value )
    {
        QString val = QString::number(value);
        QString origval = QString::number(originalvalue);
        if( setPragma(pragma, val, origval))
        {
            originalvalue = value;
        }
    }
    return false;
}

bool DBBrowserDB::loadExtension(const QString& filename)
{
    if(!isOpen())
        return false;

    // Check if file exists
    if(!QFile::exists(filename))
    {
        lastErrorMessage = tr("File not found.");
        return false;
    }

    // Try to load extension
    char* error;
    if(sqlite3_load_extension(_db, filename.toUtf8(), 0, &error) == SQLITE_OK)
    {
        return true;
    } else {
        lastErrorMessage = QString::fromUtf8(error);
        sqlite3_free(error);
        return false;
    }
}